TY - JOUR A1 - Purohit, Purv A1 - Wang, D.-Y. A1 - Wurm, Andreas A1 - Schick, C. A1 - Schönhals, Andreas T1 - Comparison of thermal and dielectric spectroscopy for nanocomposites based on polypropylene and layered double hydroxide - proof of interfaces N2 - Polymer based nanocomposites by melt blending of synthesized ZnAl-Layered Double Hydroxide (ZnAl-LDH) and polypropylene (PP) were investigated by temperature modulated differential scanning calorimetry (TMDSC). The LDH was organically modified by using a surfactant, sodium dodecylbenzene sulfonate (SDBS) to increase the interlayer spacing of the LDH, so that polymer segments can intercalate the inter layer galleries. The glass transition temperature (Tg) and the thermal relaxation strength (Δcp) were determined. The Tg remains constant for concentration till 12 wt% of LDH and a slight reduction of 3 K might be observed for 16 wt% LDH but within the experimental error. The thermal relaxation strength decreases indicating reduction in the amount of mobile polymer segments from amorphous fraction. This finding is supported by the increase in the rigid amorphous fraction (RAF) which is attributed to the polymer molecules which are in close proximity to the crystals and the LDH sheets, as they hinder their mobility. This is analyzed in detail and related to the dielectric relaxation spectroscopy (BDS) results. KW - Polypropylene KW - Layered double hydroxide KW - Nanocomposites KW - Temperature modulated differential scanning calorimetery KW - Dielectric spectroscopy KW - Rigid amorphous fraction PY - 2014 DO - https://doi.org/10.1016/j.eurpolymj.2014.03.005 SN - 0014-3057 SN - 1873-1945 VL - 55 SP - 48 EP - 56 PB - Elsevier CY - Oxford AN - OPUS4-30626 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Madkour, Sherif A1 - Garwek, Marcel A1 - Hertwig, Andreas A1 - Schönhals, Andreas T1 - Do Interfacial Layers in Thin Films Act as an Independent Layer Within Thin Films? N2 - The thermodynamic behavior of thin PVME films including the irreversible adsorbed layer on the substrate is investigated. In a first step, the growth kinetics of the adsorbed layer was studied combining a leaching technique and atomic force microscopy. Further, it was shown that there is a critical initial film thickness for the formation of a surface-filling adsorbed layer. Additionally, spectroscopic ellipsometry measurements were carried out to investigate the influence of the adsorbed layer on the glass transition temperature of the thin films. For 30 nm films and below, the influence of the adsorbed layer percolates strongly to the bulk-like layer of the film. Finally, the molecular dynamics of the adsorbed layer was studied by broadband dielectric spectroscopy, employing nanostructured-electrode systems. One process was revealed, which was assigned either to molecular fluctuations taking place in a loosely-bounded the part of the adsorbed layer, or to the desorption/adsorption of segments at the substrate. KW - Thin polymer films PY - 2021 DO - https://doi.org/10.1021/acs.macromol.0c02149 VL - 54 IS - 1 SP - 509 EP - 519 PB - ACS Publications AN - OPUS4-52037 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Szymoniak, Paulina A1 - Omar, Hassan A1 - Gawek, Marcel A1 - Hertwik, Andreas A1 - Madkour, Sherif A1 - Schönhals, Andreas T1 - Investigation of the behavior of thin polymeric films including the adsorbed layer on the substrate by nano-sized relaxation spectroscopy and complementary methods N2 - Thin polymeric films are of great importance of high number of high-tech applications for instance in sensors and nanoelectronics. Form the scientific point of view thin films with thickness below 100 nm are ideal model systems to study confinement effects on its properties for instance on the molecular relaxation processes. In this contribution an overview is presented about the behavior of different systems as investigated by nanosized relaxation spectroscopy like broadband dielectric spectroscopy employing nano structured capacitors and AC chip calorimetry complimented by ellipsometry. The systems considered are PVME1, PVME/PS blends2,3 P2VP4, PBAC5 and polysulfone6. Besides the film also the adsorbed layer on the substrate prepared by a leaching approach and investigated by AFM is considered.1,4-7. For these investigationsss it is found that the adsorbed layer itself exhibits a relaxation dynamics which might be assigned either to molecular motions or to adsorptions desorption kinetics. T2 - 9. International Discussion Meeting Relaxation Complex Systems CY - Chiba, Japan DA - 12.08.2023 KW - Thin polymer films PY - 2023 AN - OPUS4-58103 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Omar, Hassan A1 - Hertwig, Andreas A1 - Szymoniak, Paulina A1 - Schönhals, Andreas T1 - Signature of the Adsorbed Layer on the glass transition of thin polymer Films: Broadband Dielectric spectroscopy and related techniques N2 - In well annealed thin polymer films with non-repulsive polymer/substrate interaction with a substrate an irreversibly adsorbed layer is expected to form. These adsorbed layers have shown a great potential for technological applications [1]. However, the growth kinetics and the molecular mobility of the adsorbed layer is still not fully understood. This concerns also the influence of the adsorbed layer on the thickness dependence of the glass transition temperature of thin films. This is partly due to the difficult accessibility of these layers in thin films. Here, the irreversibly adsorbed layers of semi-rigid mail chain polymers like polycarbonate or polysulfone are revealed by solvent-leaching experiments. First, the growth kinetics of these layers is investigated as a function of annealing time. The film thickness, topography and the quality of the adsorbed layer is controlled by Atomic Force Microscopy (AFM). Secondly, the molecular mobility of the adsorbed layer is investigated by Broadband Dielectric Spectroscopy (BDS). A developed nanostructured capacitor arrangement is employed to measure the layer with a free surface. In addition to the dielectric experiments, spectroscopic Ellipsometry measurements are carried out to estimate the glass transition of the thin films. The thickness dependence of the glass transition of the thin films is correlated with the adsorbed layer [2,3]. Acknowledgments D. Hülagü and G. Hidde thanked for the help with the ellipsometry measurements. T2 - 12. Conference on Broabband Dielectric Spectroscopy and its Application CY - Lisbon, Portugal DA - 01.09.2024 KW - Thin films PY - 2024 AN - OPUS4-60959 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Madkour, Sherif A1 - Szymoniak, Paulina A1 - Hertwig, Andreas A1 - Heidari, M. A1 - von Klitzing, R. A1 - Napolitano, S. A1 - Sferrazza, M. A1 - Schönhals, Andreas T1 - Decoupling of dynamic and thermal glass transition in thin films of a PVME/PS blend N2 - The discussions on the nanoconfinement effect on the glass transition and glassy dynamics phenomena have yielded many open questions. Here, the thickness dependence of the thermal glass transition temperature of thin films of a PVME/PS blend is investigated by ellipsometry. Its thickness dependence was compared to that of the dynamic glass transition (measured by specific heat spectroscopy), and the deduced Vogel temperature (T0). While and T0 showed a monotonous increase, with decreasing the film thickness, the dynamic glass transition temperature () measured at a finite frequency showed a non-monotonous dependence that peaks at 30 nm. This was discussed by assuming different cooperativity length scales at these temperatures, which have different sensitivities to composition and thickness. This non-monotonous thickness dependence of disappears for frequencies characteristic for T0. Further analysis of the fragility parameter, showed a change in the glassy dynamics from strong to fragile, with decreasing film thickness. KW - Thin polymeric films KW - Ellipsometry KW - Specific heat spectroscopy PY - 2017 DO - https://doi.org/10.1021/acsmacrolett.7b00625 SN - 2161-1653 VL - 6 IS - 10 SP - 1156 EP - 1161 PB - ACS Publications AN - OPUS4-42266 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Omar, Hassan A1 - Hiid, Gundula A1 - Szymoniak, Paulina A1 - Hertwig, Andreas A1 - Schönhals, Andreas T1 - Growth kinetics of the adsorbed layer of poly(bisphenol A carbonate) and its effect on the glass transition behavior in thin films N2 - The glass transition behavior of thin films of poly(bisphenol A carbonate) (PBAC) was studied employing ellipsometry. The glass transition temperature increases with the reduction of the film thickness. This result is attributed to the formation of an adsorbed layer with a reduced mobility compared to bulk PBAC. Therefore, for the first time, the growth kinetics of the adsorbed layer of PBAC was investigated, prepared by leaching samples from a 200 nm thin film which were annealed for several times at three different temperatures. The thickness of each prepared adsorbed layer was measured by multiple scans using atomic force microscopy (AFM). Additionally, an unannealed sample was measured. Comparison of the measurements of the unannealed and the annealed samples provides proof of a pre-growth regime for all annealing temperatures which was not observed for other polymers. For the lowest annealing temperature after the pre-growth stage only a growth regime with a linear time dependence is observed. For higher annealing temperatures the growth kinetics changes from a linear to a logarithmic growth regime at a critical time. At the longest annealing times the films showed signs of dewetting where segments of the adsorbed film were removed from the substrate (dewetting by desorption). The dependence of the surface roughness of the PBAC surface on annealing time also confirmed that the films annealed at highest temperatures for the longest times desorbed from the substrate. KW - Ultra thin polymer films PY - 2023 UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-574531 DO - https://doi.org/10.1039/D3RA02020G SN - 2046-2069 VL - 13 IS - 21 SP - 14473 EP - 14483 PB - RSC Publishing CY - London AN - OPUS4-57453 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Omar, Hassan A1 - Ahamadi, Shayan A1 - Hülagü, Deniz A1 - Hidde, Gundula A1 - Hertwig, Andreas A1 - Szymoniak, Paulina A1 - Schönhals, Andreas T1 - Investigations of the adsorbed layer of polysulfone: Influence of the thickness of the adsorbed layer on the glass transition of thin films N2 - This work studies the influence of the adsorbed layer on the glass transition of thin films of polysulfone. Therefore, the growth kinetics of the irreversibly adsorbed layer of polysulfone on silicon substrates was first investigated using the solvent leaching approach, and the thickness of the remaining layer was measured with atomic force microscopy. Annealing conditions before leaching were varied in temperature and time (0–336 h). The growth kinetics showed three distinct regions: a pre-growth step where it was assumed that phenyl rings align parallel to the substrate at the shortest annealing times, a linear growth region, and a crossover from linear to logarithmic growth observed at higher temperatures for the longest annealing times. No signs of desorption were observed, pointing to the formation of a strongly adsorbed layer. Second, the glass transition of thin polysulfone films was studied in dependence on the film thickness using spectroscopic ellipsometry. Three annealing conditions were compared: two with only a tightly bound layer formed in the linear growth regime and one with both tightly bound and loosely adsorbed layers formed in the logarithmic growth regime. The onset thickness and increase in the glass transition temperature increases with annealing time and temperature. These differences were attributed to the distinct conformations of the formed adsorbed layers. KW - Glass transition KW - Adsorbed Layer PY - 2024 UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-607701 DO - https://doi.org/10.1063/5.0223415 SN - 0021-9606 VL - 161 IS - 5 SP - 1 EP - 12 PB - AIP Publishing AN - OPUS4-60770 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Leng, Jing A1 - Kang, N. A1 - Wang, D.-Y. A1 - Wurm, Andreas A1 - Schick, C. A1 - Schönhals, Andreas T1 - Crystallization behavior of nanocomposites based on poly(L-lactide) and MgAl layered double hydroxides - Unbiased determination of the rigid amorphous phases due to the crystals and the nanofiller N2 - Semicrystalline polymers have to be described by a three phase model consisting of a mobile amorphous (MAF), a crystalline (CF), and a rigid amorphous fraction (RAF). For nanocomposites based on a semicrystalline polymer the RAF is due to both the crystallites (RAFcrystal) and the filler (RAFfiller). Polymer nanocomposite based on poly(L-lactide) and MgAl layered double hydroxide nanofiller were prepared. Due to the low crystallization rate of PLA ist crystallization can be suppressed by a high enough cooling rate, and the RAF is due only to the nanofiller. The MAF, CF, and RAF were estimated by Temperature Modulated DSC. For the first time CF, MAF, RAFcrystal, and RAFfiller could be estimated. It was found, that RAFfiller increases linearly with the concentration of the nanofiller for this system. Furthermore, RAFcrystal is only slightly influenced by the presence of the nanofiller. KW - Polymer based nanocomposites PY - 2017 DO - https://doi.org/10.1016/j.polymer.2016.11.065 SN - 0032-3861 SN - 1873-2291 VL - 108 SP - 257 EP - 264 PB - Elesevier AN - OPUS4-39052 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Friedrich, Jörg Florian A1 - Kühn, Gerhard A1 - Mix, Renate A1 - Fritz, Andreas A1 - Schönhals, Andreas T1 - Polymer surface modification with monofunctional groups of variable types and densities N2 - The retention of chemical structure and functional groups during pulsed plasma polymerization was used for producing adhesion-promoting plasma polymer layers with high concentrations of exclusively one kind of functional groups, such as OH, NH2, or COOH. The maximum content of functional groups was 31 OH using allyl alcohol, 18 NH2 using allylamine, or 24 COOH per 100 C atoms using acrylic acid. To vary the density of functional groups, chemical co-polymerization with ethylene as 'chain-extending' co-monomer, or butadiene as 'chemical crosslinker' was initiated in the pulsed plasma. The composition of these co-polymers was investigated by XPS and IR spectroscopy. The concentrations of functional groups were measured by derivatizing with fluorine-containing reagents and using XPS. A set of plasma parameters was found to be a good compromise between a high number of functional groups and complete insolubility in water, ethanol or THF,which is needed for further chemical processing. Here, these monotype-functionalized surfaces were used in metal-polymer systems as adhesion-promoting interlayers to examine the influence of type and density of functional groups on adhesion. As expected, COOH- and OH-group-terminated interlayers showed maximum peel strengths to evaporated aluminium layers. The adhesion increased linearly with the number of OH groups to a maximum at about 27 OH per 100 C atoms. Higher concentrations of OH groups did not increase the peel strength further. KW - Co-polymers KW - Adhesion-promoting interlayers KW - Metal-polymer systems PY - 2003 DO - https://doi.org/10.1163/156856103322396695 SN - 0169-4243 SN - 1568-5616 VL - 17 IS - 12 SP - 1591 EP - 1617 PB - VNU Science Press CY - Utrecht AN - OPUS4-2704 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Friedrich, Jörg Florian A1 - Schönhals, Andreas A1 - Fritz, Andreas A1 - Mix, Renate A1 - Kühn, Gerhard ED - d'Agostino, R. T1 - Pulsed plasma initiated homo and copolymerisation - characterization of thin plasma polymer layers by dielectric relaxation spectroscopy T2 - 16th International Symposium on Plasma Chemistry (ISPC-16) CY - Taormina, Italy DA - 2003-06-22 PY - 2003 IS - CD-ROM PB - Dep. of Chemistry, Univ. CY - Bari AN - OPUS4-2711 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Fritz, Andreas A1 - Schönhals, Andreas A1 - Mix, Renate A1 - Kühn, Gerhard A1 - Friedrich, Jörg Florian T1 - Dielectric spectroscopy of plasma copolymers of the system allyl alcohol/alkene N2 - Polymers synthesized with plasma techniques are very interesting materials for electronic, optic, and bio compatible applications. Thin films of plasma polymers shows a good adhesion to metals, glass, or other polymers. But the supramolecular structure, the durability, and the chemical and mechanical behavior of these polymers is poorly understood. Therefore dielectric investigations are carried out to study the dynamic behavior of the plasma polymers. As polymer system allyl alcohol/alkene is chosen to get polymers with a defined concentration of hydroxyl groups. The dielectric investigations shows several relaxation processes and a dependency of the dielectric parameters from the ratio of allyl alcohol in the polymer is observed. This results indicated that the alkene monomers were assembled continuous into the polymer matrix. T2 - Frühjahrstagung des Arbeitskreises Festkörperphysik bei der DPG CY - Regensburg, Deutschland DA - 2002-03-11 PY - 2002 UR - http://old.dpg-tagungen.de/archive/2002/cpp_4.html SN - 0420-0195 SN - 0372-5448 SN - 0343-9216 IS - CPP 4.7 SP - 424 CY - Bad Honnef AN - OPUS4-2057 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Fritz, Andreas A1 - Schönhals, Andreas A1 - Mix, Renate A1 - Kühn, Gerhard A1 - Friedrich, Jörg Florian T1 - Dielectric spectroscopy of plasma copolymers or the system allyl alcohol/alkene T2 - Frühjahrstagung des Arbeitskreises Festkörperphysik bei der DPG CY - Regensburg, Germany DA - 2002-03-11 PY - 2002 SN - 0420-0195 SN - 0372-5448 SN - 0343-9216 IS - CPP 4.7 SP - 424 CY - Bad Honnef AN - OPUS4-2058 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Fritz, Andreas A1 - Schönhals, Andreas A1 - Sapich, B. A1 - Stumpe, J. T1 - Dynamic and photochemical behavior of amorphous comb-like copolymers with photochromic azobenzene side groups N2 - A series of amorphous photochromic homo- and copolymethacrylates with an azobenzene moiety in the side group is investigated systematically by optical and dielectric spectroscopy. The aliphatic ester component of the comonomer unit and the concentration of the azobenzene groups within the copolymer are varied. The kinetics and the temperature dependence of the E/Z (trans/cis) photoisomerization and of the thermal Z/E (cis/trans) isomerization is studied for spin-coated films of the polymers. To understand the polarity of the polymeric materials as well as the matrix dependence of the reactions and of the photoinduced reorientation processes in the steady state molecular dynamics is investigated by dielectric spectroscopy. A variety of relaxation processes is observed: a γ-relaxation at low temperatures followed by a β-, an α-, and a δ-process. Additionally at room temperature a new -relaxation is detected for polymers containing azobenzene moieties. The temperature dependence of the reaction rate of the thermal Z/E isomerization process measured by optical spectroscopy seems to correlate with the values of the β'-process. A correspondence between dielectric and photochemical behavior is discussed. PY - 1999 SN - 1022-1352 SN - 1521-3935 VL - 200 IS - 10 SP - 2213 EP - 2220 PB - Wiley-VCH Verl. CY - Weinheim AN - OPUS4-13687 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Schönhals, Andreas A1 - Fritz, Andreas A1 - Pfeiffer, K. T1 - Characterization of the crosslinking kinetics of a thin polymeric layer by real-time dielectric relaxation spectroscopy N2 - The crosslinking kinetic of a thin polymeric layer based on a prepolymer of a phthalic aciddiallylester was studied by real-time dielectric spectroscopy in the frequency range from 10-1 to 105 Hz. With increasing reaction time the real part of the dielectric function ε ´ decreases. The time dependence of ε ´ can be described by a stretched exponential function with a stretching exponent of 0.5. This means that the influence of the chemical reaction on ε ´ cannot be described by a first order kinetic. From the temperature dependence of the characteristic time constant an activation energy of 71 kJ/mol could be estimated for the reaction. From the dielectric loss data the change of the relaxation rate of the dynamic glass transition fpα with the reaction time is obtained. After a temperature dependent induction period fpα decreases very strongly. No plateau value which corresponds to a glass transition in the crosslinked system is obtained for long reaction times. PY - 2001 SN - 1022-1352 SN - 1521-3935 VL - 202 IS - 16 SP - 3228 EP - 3233 PB - Wiley-VCH Verl. CY - Weinheim AN - OPUS4-13698 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Sapich, B. A1 - Fischer, T. A1 - Haferkorn, J. A1 - Geue, T. A1 - Fritz, Andreas A1 - Schönhals, Andreas A1 - Date, R. A1 - Fawcett, A. A1 - Stumpe, J. T1 - Anisotropic films of poly(olefin sulfone)s with cinnamoyl side groups prepared by self-organisation and photoreactions T2 - Liquid Crystals and its practical application PY - 2006 VL - 4 IS - 18 SP - 9 EP - 21 AN - OPUS4-14594 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Schönhals, Andreas A1 - Hardy, L. A1 - Fritz, Andreas A1 - Stevenson, I. A1 - Boiteux, G. A1 - Seytre, G. T1 - Dielectric relaxation behaviour of poly(ethylene naphthalene 2,6 dicarboxylate) (PEN) N2 - Dielectric spectroscopy has been used to study poly(ethylene naphthalene 2,6 dicarboxylate) (PEN) samples of different morphologies obtained by thermally treating bi-axially stretched PEN films. Neat and thermally treated samples of PEN films have been characterised by differential scanning calorimetry in order to measure the glass transition and melting temperatures as well as the degrees of crystallinity. Dielectric analysis has allowed the observation of the evolution of molecular relaxation phenomena with morphology changes and has revealed three relaxation processes: ?-, ?*- and ?-relaxation (increasing temperature). The ?-relaxation is associated with local motions of ester and the ?*-relaxation with partially cooperative motions of naphthalene groups. The latter has been shown to be related to the morphology of the materials under study. The ?-relaxation associated to the glass transition of PEN corresponds to cooperative motions induced by conformational rearrangements of the main chain and depends also on the morphology of the PEN films. Dielectric relaxation behaviours were compared using the activation energies calculated from Arrhenius equation formalism for the two sub-glass processes. Vogel–Fulcher–Tammann fits were performed on the ?-relaxation. Our important contribution for the bi-axially stretched PEN films study is related to the assignment of the ?*-relaxation that can be attributed to naphthalene aggregates. PY - 2002 DO - https://doi.org/10.1016/S0022-3093(02)01104-3 SN - 0022-3093 VL - 305 SP - 174 EP - 182 PB - North-Holland Publ. Co. CY - Amsterdam AN - OPUS4-1570 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Gawek, Marcel A1 - Szymoniak, Paulina A1 - Hülagü, Deniz A1 - Hertwig, Andreas A1 - Schönhals, Andreas T1 - Molecular Mobility of Thin Films and the Adsorbed Layer of Poly(2-vinylpyridine) N2 - The molecular dynamics of thin films and the adsorbed layer of poly(2-vinylpyridine) (P2VP) were investigated using broadband dielectric spectroscopy (BDS) and spectroscopic ellipsometry. Thin films of P2VP were prepared on silicon substrates and characterized to understand the influence of film thickness on the thermal glass transition temperature (Tg) and molecular mobility. The ellipsometric study revealed a decrease in Tg with decreasing film thickness, attributed to the enhanced mobility at the polymer/air interface. The adsorbed layer, prepared via the solvent leaching approach, exhibited a higher Tg compared to the bulk, indicating reduced molecular mobility due to strong polymer substrate interactions. The dielectric measurements were carried out in two different electrode configurations, crossed electrode capacitors (CEC) and nanostructured electrodes (NSE), where the latter allows for a free surface layer at the polymer/air interface. The relaxation rates of the α-relaxation measured in the CEC geometry collapse into one chart independent from the film thickness. For the thin films measured in the NSE arrangement the relaxation rates slow down with decreasing film thickness which was discussed as related to a stronger interaction of the P2VP segments with the native SiO2 at the surface of the silicon substrate compared to aluminum. It is worth to note that the effect of the enhanced mobility at the polymer/air interface is not observed in the dielectric measurements. BDS measurements in NSE geometry identified an additional relaxation process (α*-relaxation) in thin films, which was more pronounced in the adsorbed layer. This process is hypothesized to be related to molecular fluctuations within the adsorbed layer including the adsorption/desorption dynamics of segments or to a Slow Arrhenius Process (SAP) related to the equilibration dynamics deep in the glassy state. KW - Thin polymer films PY - 2025 UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-637181 DO - https://doi.org/10.1039/d5sm00539f SN - 1744-6848 SP - 1 EP - 12 PB - Royal Society of Chemistry (RSC) AN - OPUS4-63718 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Schönhals, Andreas A1 - Goering, Harald A1 - Böhning, Martin A1 - Fritz, Andreas A1 - Rübner, J. T1 - Structure Analysis of Polymeric Nanomaterials by Relaxation Spectroscopy T2 - Polydays 2002 CY - Berlin, Germany DA - 2002-09-30 PY - 2002 SP - 1(?) AN - OPUS4-2044 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Böhning, Martin A1 - Goering, Harald A1 - Fritz, Andreas A1 - Brzezinka, Klaus-Werner A1 - Turky, Gamal A1 - Schönhals, Andreas A1 - Schartel, Bernhard T1 - Dielectric Study of Molecular Mobility in Poly(propylene-graft-maleic anhydride)/Clay Nanocomposites N2 - Polymer/clay nanocomposite materials based on poly(propylene-graft-maleic anhydride) (PPgMAH) and two different organophilic modified clays were investigated by dielectric relaxation spectroscopy (DRS). In contrast to ungrafted polypropylene (PP), PPgMAH shows a dielectrically active relaxation process which can be assigned to localized fluctuations of the polar maleic anhydride groups. Its relaxation rate exhibits an unusual temperature dependence, which could be attributed to a redistribution of water molecules in the polymeric matrix. This is confirmed by a combination of Raman spectroscopy and thermogravimetric experiments (TGA) with real-time dielectric measurements under controlled atmospheres. In the nanocomposites this relaxation process is shifted to higher frequencies up to 3 orders of magnitude compared to the unfilled polymer. This indicates a significantly enhanced molecular mobility in the interfacial regions. In the nanocomposite materials a separate high-temperature process due to Maxwell-Wagner-Sillars (MWS) polarization was observed. The time constant of this MWS process can be correlated with characteristic length scales in nanocomposites and therefore provides additional information on dispersion and delamination/exfoliation of clay platelets in these materials. These properties also influence the diffusivity of the water molecules as revealed by real-time dielectric investigations. KW - Polymer clay nanocomposites KW - Molecular mobility KW - Dielectric relaxation spectroscopy PY - 2005 DO - https://doi.org/10.1021/ma048315c SN - 0024-9297 SN - 1520-5835 VL - 38 IS - 7 SP - 2764 EP - 2774 PB - American Chemical Society CY - Washington, DC AN - OPUS4-7281 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Said Shabaan Omara, Shereen A1 - Rehim, M.H.A. A1 - Ghoneim, A. A1 - Madkour, Sherif Aly Hassan Aly A1 - Thünemann, Andreas A1 - Turky, G. A1 - Schönhals, Andreas T1 - Structure-property relationships of hyperbranched polymer/kaolinite nanocomposites N2 - Two methods were employed to prepare hyperbranched polyamine ester (HPAE)/kaolinite (Ka) nanocomposites resulting in different morphologies. In the case of the in situ polymerization, diethanolamine is inserted as monomer between the Ka layers and polymerized with methyl acrylate to prepare HPAE/Ka–DEA nanocomposites. For the ex situ method, Ka is modified with dodecylamine and solution-blended with HPAE. The former method leads to an intercalated morphology where the latter approach results in an exfoliated structure, as proofed by SAXS and TEM. A complementary combination of methods like differential scanning calorimetry (DSC), broadband dielectric relaxation (BDS), and specific heat spectroscopy (SHS) was used to investigate both kinds of nanocomposites in detail. Above Tg, the dielectric spectra are dominated by the conductivity contribution while the segmental dynamics is retrieved by SHS. A comparison of the temperature dependencies reveals a decoupling of segmental dynamics and conductivity, which becomes weaker with decreasing fragility. PY - 2015 DO - https://doi.org/10.1021/acs.macromol.5b01693 SN - 0024-9297 SN - 1520-5835 VL - 48 IS - 18 SP - 6562 EP - 6573 PB - American Chemical Society CY - Washington, DC AN - OPUS4-34424 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Omara, Shereen Shabaan A1 - Turky, G. A1 - Ghoneim, A. A1 - Thünemann, Andreas A1 - Abdel Rehim, M. H. A1 - Schönhals, Andreas T1 - Hyperbranched poly(amidoamine)/kaolinite nanocomposites: Structure and charge carrier dynamics N2 - An ex-situ approach was applied to prepare nanocomposites from hyperbranched poly(amidoamine) and modified kaolinite (Ka-DCA). The structure of the polymer and the corresponding nanocomposites was investigated by FTIR, DSC, SAXS and TEM. SAXS might suggest a partly exfoliated structure of the nanocomposites, which was supported by TEM. The molecular dynamics was studied by means of broadband dielectric spectroscopy (BDS). The dielectric spectra are dominated by a conductivity contribution at higher temperatures for all samples investigated. The obtained results further indicated that DC conductivity is increased by 4 orders of magnitude with increasing concentration of Ka-DCA nanofiller. Further, a significant separation between the conductivity relaxation time and that of segmental dynamics was observed. The decoupling phenomenon and the conductivity mechanism were discussed in detail. This study provides insights about the influence of the nanofiller on the structure and the conductivity contribution of nanocomposites of hyperbranched polymers including the decoupling phenomenon and fragility. KW - Hyperbranched polymers KW - Nanocomposites KW - Conductivity PY - 2017 DO - https://doi.org/10.1016/j.polymer.2017.06.017 SN - 0032-3861 VL - 121 SP - 64 EP - 74 PB - Elsevier Ltd. AN - OPUS4-40648 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Purohit, Purv A1 - Huacuja Sánchez, Jesús A1 - Wang, D.-Y. A1 - Emmerling, Franziska A1 - Thünemann, Andreas A1 - Heinrich, G. A1 - Schönhals, Andreas T1 - Structure - property relationships of nanocomposites based on polypropylene and layered double hydroxides N2 - Nanocomposites based on polypropylene (PP) and organically modified ZnAl layered double hydroxides (ZnAl-LDH) were prepared by melt blending and investigated by a combination of differential scanning calorimetry (DSC), small- and wide-angle X-ray scattering (SAXS and WAXS), and dielectric relaxation spectroscopy (DRS). An average number of stack size of LDH layers is calculated by analyzing the SAXS data which is close to that of pure organically modified ZnAl-LDH. Scanning microfocus SAXS investigations show that the ZnAl-LDH is homogeneously distributed in the PP matrix as stacks of 4–5 layers with an intercalated morphology. DSC and WAXS results show that the degree of crystallinity decreases linearly with the increasing content of LDH. The extrapolation of this dependence to zero estimates a limiting concentration of ca. 40% LDH where the crystallization of PP is completely suppressed by the nanofiller. The dielectric spectra of the nanocomposites show several relaxation processes which are discussed in detail. The intensity of the dynamic glass transition (β-relaxation) increases with the concentration of LDH. This is attributed to the increasing concentration of the exchanged anion dodecylbenzenesulfonate (SDBS) which is adsorbed at the LDH layers. Therefore, a detailed analysis of the β-relaxation provides information about the structure and the molecular dynamics in the interfacial region between the LDH layers and the polypropylene matrix which is otherwise dielectrically invisible (low dipole moment). As a main result, it is found that the glass transition temperature in this interfacial region is by 30 K lower than that of pure polypropylene. This is accompanied by a drastic change of the fragility parameter deduced from the relaxation map. KW - Nanocomposites KW - Layered double hydroxide KW - Dielectric spectroscopy KW - X-ray scattering KW - Polypropylene PY - 2011 DO - https://doi.org/10.1021/ma200323k SN - 0024-9297 SN - 1520-5835 VL - 44 IS - 11 SP - 4342 EP - 4354 PB - American Chemical Society CY - Washington, DC AN - OPUS4-23921 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Purohit, Purv A1 - Wang, D.-Y. A1 - Emmerling, Franziska A1 - Thünemann, Andreas A1 - Heinrich, G. A1 - Schönhals, Andreas T1 - Arrangement of layered double hydroxide in a polyethylene matrix studied by a combination of complementary methods N2 - Organically modified ZnAl Layered Double Hydroxides (ZnAl-LDH) was synthesized and melt blended with polyethylene to obtain nanocomposites. The resulting morphology was investigated by a combination of Differential Scanning Calorimetry (DSC), Small and Wide-angle X-ray scattering (SAXS and WAXS) and dielectric relaxation spectroscopy (DRS). The arrangement (intercalation) of polyethylene chains between LDH stacks was investigated employing SAXS. The homogeneity of the nanocomposites and average number of stack size (4–6 layers) were determined using scanning microfocus SAXS (BESSY II). DSC and WAXS results show that the degree of crystallinity decreases linearly with the increasing content of LDH. The extrapolation of this dependence to zero estimates a limiting concentration of ca. 45% LDH where the crystallization of PE is completely suppressed by the nanofiller. The dielectric spectra of the nanocomposites show several relaxation processes which are discussed in detail. The intensity of the dynamic glass transition (β-relaxation) increases with the concentration of LDH. This is attributed to the increasing concentration of the exchanged anion sodium dodecylbenzene sulfonate (SDBS) which is adsorbed at the LDH layers. Therefore, a detailed analysis of the β-relaxation provides information about the structure and the molecular dynamics in the interfacial region between the LDH layers and the polyethylene matrix which is otherwise dielectrically invisible (low dipole moment). KW - Dielectric spectroscopy KW - Polyethylene nanocomposites KW - Layered double hydroxides PY - 2012 DO - https://doi.org/10.1016/j.polymer.2012.03.041 SN - 0032-3861 SN - 1873-2291 VL - 53 IS - 11 SP - 2245 EP - 2254 PB - Springer CY - Berlin AN - OPUS4-25810 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Krause, Christina A1 - Yin, Huajie A1 - Cerclier, C. A1 - Morineau, D. A1 - Wurm, Andreas A1 - Schick, C. A1 - Emmerling, Franziska A1 - Schönhals, Andreas T1 - Molecular dynamics of a discotic liquid crystal investigated by a combination of dielectric relaxation and specific heat spectroscopy N2 - The molecular dynamics of the discotic liquid crystal pyrene-1,3,6,8-tetracarboxylic tetra(2-ethylhexyl)ester is studied by dielectric relaxation and specific heat spectroscopy. Dielectric spectroscopy shows 3 processes: a β-relaxation at low temperatures and an α-relaxation in the temperature range of the mesophases followed by conductivity. The dielectric α-relaxation is assigned to a restricted glassy dynamics in the plastic crystal as well as in the liquid crystalline phase. The obtained different Vogel–Fulcher–Tammann laws (different Vogel temperatures and fragility) are related to the different restrictions of the dipolar fluctuations in the corresponding phases. By means of specific heat spectroscopy glassy dynamics is also detected in the plastic crystalline phase but with quite a different temperature dependence of the relaxation times. This is discussed considering the different probes involved and how they are influenced by the structure. In the frame of the fluctuation approach a correlation length of glassy dynamics is calculated to 0.78 nm which corresponds to the core–core distance estimated by X-ray scattering. PY - 2012 DO - https://doi.org/10.1039/c2sm25610j SN - 1744-683X VL - 8 IS - 43 SP - 11115 EP - 11122 PB - RSC Publ. CY - Cambridge AN - OPUS4-26826 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Leng, Jing A1 - Purohit, Purv A1 - Kang, N. A1 - Wang, D.-Y. A1 - Falkenhagen, Jana A1 - Emmerling, Franziska A1 - Thünemann, Andreas A1 - Schönhals, Andreas T1 - Structure-property relationships of nanocomposites based on polylactide and MgAl layered double hydroxides N2 - Nanocomposites based on poly(ʟ-lactide) (PLA) and organically modified MgAl Layered Double Hydroxides (MgAl-LDH) were prepared by melt blending and investigated by a combination of Differential Scanning Calorimetry (DSC), Small- and Wide-Angle X-ray Scattering (SAXS, WAXS), and dielectric spectroscopy (BDS). Scanning microfocus SAXS investigations show that the MgAl-LDH is homogeneously distributed in the matrix as stacks of 6 layers and/or partly exfoliated layers. DSC and WAXS show that the degree of crystallinity decreases linearly with the content of LDH. The extrapolation of the dependencies (DSC and WAXS) to zero estimates a limiting concentration of LDH CCri of ca. 21 wt% where the crystallization of PLA is completely suppressed by the nanofiller. The dielectric behavior of neat PLA show two relaxation regions, a β-relaxation at low temperatures related to localized fluctuations and the α-relaxation at higher temperatures due to the dynamic glass transition. The dielectric spectra of the nanocomposites show several additional relaxation processes compared to neat PLA which are discussed in detail. For the nanocomposites around 260 K (ƒ = 1 kHz) an additional process is observed which intensity increases with increasing concentration of LDH. This process is mainly attributed to the exchanged dodecylbenzene sulfonate (SDBS) molecules which are adsorbed at the LDH layers and form a mixed phase with the polymer close to the layers and stacks. An analysis of this process provides information about the molecular dynamics in the interfacial region between the LDH layers and the PLA matrix which reveal glassy dynamics in this region. In the temperature range around 310 K (ƒ = 1 kHz) a further process is observed. Its relaxation rate has an unusual saddle-like temperature dependence. It was assigned to rotational fluctuations of water molecules in a nanoporous environment provided by the LDH filler. Above the glass transition temperature a further process is observed at temperatures above. It is related to Maxwell/Wagner/Sillars polarization due to the blocking of charges at the nanofiller. KW - Polymer based nanocomposites KW - Polylactide KW - Layered double hydroxides KW - Dielectric spectroscopy PY - 2015 DO - https://doi.org/10.1016/j.eurpolymj.2015.05.008 SN - 0014-3057 SN - 1873-1945 VL - 68 SP - 338 EP - 354 PB - Elsevier CY - Oxford AN - OPUS4-33257 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Leng, Jing A1 - Kang, Nianjun A1 - Wang, De-Yi A1 - Falkenhagen, Jana A1 - Thünemann, Andreas A1 - Schönhals, Andreas T1 - Structure–Property Relationships of Nanocomposites Based on Polylactide and Layered Double Hydroxides – Comparison of MgAl and NiAl LDH as Nanofiller N2 - Nanocomposites based on poly(L-lactide) (PLA) and organically modified Ni/Al layered double hydroxides (NiAl/LDHs) are prepared by melt blending and investigated by a combination of size exclusion chromatography, differential scanning calorimetry (DSC), small-angle X-ray scattering (SAXS), wide-angle X-ray scattering, and broadband dielectric spectroscopy. A detailed comparison to the behavior of the corresponding MgAl/LDH–PLA nanocomposites is made. SAXS investigations show that the morphology of the NiAl/LDH–PLA nanocomposites is more intercalated compared to the MgAl/LDH based PLA nanocomposite, which is more exfoliated. The DSC investigation gives a different dependence of the degree of crystallization on the concentration of LDH for NiAl/LDH–PLA than for MgAl/LDH–PLA nanocomposite system. These differences are discussed taking the differences of the morphologies of both systems into account. Broadband dielectric spectroscopy reveals information about the molecular dynamics where essential differences are observed for all relaxation processes taking place in both systems which were related to the different morphologies. KW - Nanocomposites KW - Polylactide PY - 2017 DO - https://doi.org/10.1002/macp.201700232 SN - 1022-1352 SN - 1521-3935 VL - 218 IS - 20 SP - Article 1700232, 1 EP - 12 PB - Wiley-VCH Verlag AN - OPUS4-42597 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Szymoniak, Paulina A1 - Pauw, Brian Richard A1 - Qu, Xintong A1 - Schönhals, Andreas T1 - Competition of nanoparticle-induced mobilization and immobilization effects on segmental dynamics of an epoxy-based nanocomposite N2 - The complex effects of nanoparticles on a thermosetting material based on an anhydride cured DGEBA/Boehmite nanocomposite with different particle concentrations is considered. A combination of X-ray scattering, calorimetry, including fast scanning calorimetry as well as temperature modulated calorimetry and dielectric spectroscopy, was employed to study the structure, the vitrification kinetics and the molecular dynamics of the nanocomposites. For the first time in the literature for an epoxy-based composite a detailed analysis of the X-ray data was carried out. Moreover, the unfilled polymer was found to be intrinsically heterogeneous, showing regions with different crosslinking density, indicated by two separate dynamic glass transitions. The glass transition temperature decreases with increasing nanoparticle concentration, resulting from a change in the crosslinking density. Moreover, on the one hand, for nanocomposites the incorporation of nanofiller increased the number of mobile segments for low nanoparticle concentrations, due to the altered crosslinking density. On the other hand, for higher loading degrees the number of mobile segments decreased, resulting from the formation of an immobilized interphase (RAF). The simultaneous mobilization and immobilization of the segmental dynamics cannot be separated unambiguously. Taking the sample with highest number of mobile segments as reference state it was possible to estimate the amount of RAF. KW - Nanocomposite PY - 2020 DO - https://doi.org/10.1039/d0sm00744g SN - 1744-683X VL - 16 IS - 23 SP - 5406 EP - 5421 PB - Royal Chemical Society AN - OPUS4-50883 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Yildirim, Arda A1 - Krause, Christina A1 - Zorn, R. A1 - Lohstroh, W. A1 - Schneider, G. J. A1 - Zamponi, M. A1 - Holerer, O. A1 - Frick, B. A1 - Schönhals, Andreas T1 - Complex molecular dynamics of a symmetric model discotic liquid crystal revealed by broadband dielectric, thermal and neutron spectroscopy N2 - The molecular dynamics of the triphenylene-based discotic liquid crystal HAT6 is investigated by broadband dielectric spectroscopy, advanced dynamical calorimetry and neutron scattering. Differential scanning calorimetry in combination with X-ray scattering reveals that HAT6 has a plastic crystalline phase at low temperatures, a hexagonally ordered liquid crystalline phase at higher temperatures and undergoes a clearing transition at even higher temperatures. The dielectric spectra show several relaxation processes: a localized gamma-relaxation a lower temperature and a so called alpha-2-relaxation at higher temperatures. The relaxation rates of the alpha-2-relaxation have a complex temperature dependence and bear similarities to a dynamic glass transition. The relaxation rates estimated by hyper DSC, Fast Scanning calorimetry and AC Chip calorimetry have a different temperature dependence than the dielectric alpha-2-relaxation and follows the VFT-behavior characteristic for glassy dynamics. Therefore, this process is called alpha-1-relaxation. Its relaxation rates show a similarity with that of polyethylene. For this reason, the alpha-1-relaxation is assigned to the dynamic glass transition of the alkyl chains in the intercolumnar space. Moreover, this process is not observed by dielectric spectroscopy which supports its assignment. The alpha-2-relaxation was assigned to small scale translatorial and/or small angle fluctuations of the cores. The neutron scattering data reveal two relaxation processes. The process observed at shorter relaxation times is assigned to the methyl group rotation. The second relaxation process at longer time scales agree in the temperature dependence of its relaxation rates with that of the dielectric gamma-relaxation. KW - Discotic Liquid Crystals PY - 2020 DO - https://doi.org/10.1039/c9sm02487e VL - 16 IS - 8 SP - 2005 EP - 2016 PB - Royal Chemical Society AN - OPUS4-50466 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Madkour, Sherif A1 - Szymoniak, Paulina A1 - Heidari, Mojdeh A1 - von Klitzing, Regine A1 - Schönhals, Andreas T1 - Evidence of a three-layered structure in ultra-thin PVME and PVME/PS blend films by nano-sized relaxation spectroscopy N2 - Despite the many controversial discussions about the nanometric confinement effect and the predictions of the three-layer model, much remain not understood and/or experimentally unproven. Here, a combination of Broadband Dielectric Spectroscopy (BDS), Specific Heat Spectroscopy (SHS), and ellipsometry was utilized to investigate the glassy dynamics of ultra-thin films of Poly (vinyl methyl ether) (PVME) and PVME/Polystyrene (PS) 50:50 wt-% miscible blend (thicknesses: 8nm - 200nm). For BDS measurements, a recently developed nano-structured sample arrangement; where ultra-thin films are spin-coated on an ultra-flat highly conductive silicon wafer and sandwiched between a wafer with nanostructured silica nano-spacers, was used. For PVME films, two processes were observed and interpreted to be the α-processes of a bulk-like layer and an absorbed layer to the substrate. BDS and SHS showed that glassy dynamics are bulk-like. However, for films lower than 15nm, BDS showed weakly slowed dynamics. For PVME/PS blend, by a self-assembling process, a nanometer-thin surface layer with a higher molecular mobility is formed at the polymer/air interface. By measuring the dynamic Tg in dependence on the film thickness, both BDS and SHS, showed that the Tg of the whole film was strongly influenced by that nanometer thick surface layer, with a lower Tg. T2 - 80. Jahrestagung der DPG und DPG-Frühjahrstagung CY - Regensburg DA - 06.03.2016 KW - Ultra-thin films PY - 2016 AN - OPUS4-35540 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Schönhals, Andreas T1 - Polymer based nanocomposites - Interplay between interfacial and bulk effects T2 - Workshop about Nanocomposites, Technical University of Athens CY - Athens, Greece DA - 2015-06-16 PY - 2015 AN - OPUS4-34315 LA - deu AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Schönhals, Andreas T1 - Influence of a nanoscale confinement on the dynamics of a discotic liquid crystal T2 - Neutron Scattering on Nano-Structured Soft Matter: Synthetic- and Bio.Materials CY - Tutzing, Germany DA - 2015-10-05 PY - 2015 AN - OPUS4-34569 LA - deu AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Madkour, Sherif Aly Hassan Aly A1 - Yin, Huajie A1 - Füllbrandt, Marieke A1 - Schönhals, Andreas T1 - Calorimetric evidence for a mobile surface layer in ultrathin polymeric films: poly(2-vinyl pyridine) N2 - Specific heat spectroscopy was used to study the dynamic glass transition of ultrathin poly(2-vinyl pyridine) films (thicknesses: 405–10 nm). The amplitude and the phase angle of the differential voltage were obtained as a measure of the complex heat capacity. In a traditional data analysis, the dynamic glass transition temperature Tg is estimated from the phase angle. These data showed no thickness dependency on Tg down to 22 nm (error of the measurement of ±3 K). A derivative-based method was established, evidencing a decrease in Tg with decreasing thickness up to 7 K, which can be explained by a surface layer. For ultrathin films, data showed broadening at the lower temperature side of the spectra, supporting the existence of a surface layer. Finally, temperature dependence of the heat capacity in the glassy and liquid states changes with film thickness, which can be considered as a confinement effect. PY - 2015 DO - https://doi.org/10.1039/c5sm01558h SN - 1744-683X VL - 11 IS - 40 SP - 7942 EP - 7952 PB - RSC Publ. CY - Cambridge AN - OPUS4-34605 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - GEN A1 - Yin, Huajie A1 - Madkour, Sherif Aly Hassan Aly A1 - Schönhals, Andreas ED - Kremer, F. T1 - Glass transition of ultra-thin polymer films: A combination of relaxation spectroscopy with surface analytics N2 - The glass transition behavior of ultra-thin supported polymer films is discussed controversially in the literature for around 20 years. Substantial efforts have been archived to understand it. In this contribution, a combination of methods sensitive to bulk properties of a system, like dielectric or specific heat spectroscopy with surface analytics, for instance, atomic force microscopy (AFM), contact angle measurements, and X-ray photoelectron spectroscopy (XPS) were employed to study the glass transition of ultra-thin supported films. All investigations were carried out on identically prepared and treated samples. Different systems with different complexities going from more or less flexible homopolymers over rigid main chain macromolecules to polymer blends have been studied. For the investigated flexible macromolecules, the dynamic glass transition temperature estimated within the frame of the linear response approach is independent of the film thickness down to several nanometers and identical to the bulk value. For polystyrene it was found the thermal glass transition temperatures can depend on the film thickness. This different behavior is not well understood till now and needs further experimental clarification. For the investigated main chain polymers polycarbonate and polysulfone. Dynamic and thermal glass transition temperature estimated from the dielectric measurements increases with decreasing film thickness. This is discussed in the frame of a strong interaction of the polymer segments with the surface of the substrate. In general for homopolymers, the interaction energy of the polymer segments with the substrate surface cannot be considered as the only parameter, which is responsible for the change in the thermal glass transition with the film thickness. For the investigated miscible blend system of polystyrene/poly(vinyl methyl ether) at a composition of 50/50 wt-% a decrease of the dynamic glass transition temperature with decreasing film thickness is found. This is explained by the formation of a poly(vinyl methyl ether)-rich surface layer with a higher molecular mobility. KW - Broadband dielectric spectroscopy KW - Specific heat spectroscopy KW - Photoelectron spectroscopy KW - Contact angle measurements KW - Polystyrene KW - Poly(vinyl methyl ether) KW - Poly(2-vinylpyridine) KW - Polycarbonate KW - Polysulfone KW - Polystyrene/ Poly(vinyl methyl ether) blend PY - 2014 SN - 978-3-319-06099-6 SN - 978-3-319-06100-9 DO - https://doi.org/10.1007/978-3-319-06100-9_2 SN - 2190-930X SN - 2190-9318 SP - 17 EP - 59 PB - Springer AN - OPUS4-31078 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Schönhals, Andreas T1 - Structure and Dynamics of Calamitic and Discotic Liquid Crystals in the Bulk and in Nanoconfinement T2 - 13. Lähnwitzseminar on Calorimetry CY - Rostock-Warnemünde, Germany DA - 2014-06-15 PY - 2014 AN - OPUS4-31080 LA - deu AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Schönhals, Andreas T1 - Relaxation Phenomena and Cooperative Length Scale at Dynamic Glass Transition in Glass Forming Liquids T2 - Condensed Matter in Paris 2014 CY - Paris, France DA - 2014-08-24 PY - 2014 AN - OPUS4-31081 LA - deu AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Schönhals, Andreas T1 - Quasi- and Inelastic Neutron Scattering to Investigate the Molecular Dynamics of Discotic Liquid Christals in the Bulk and in the Nanoconfined State T2 - QENS2014/WINS2014 CY - Autrans, France DA - 2014-05-11 PY - 2014 AN - OPUS4-31016 LA - deu AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Fahmy, Alaa A1 - Schönhals, Andreas T1 - Reaction of CO2 gas with (radicals in) plasma-polymerized acrylic acid (and formation of COOH-rich polymer layers) N2 - In contrast to most of the existing literature on plasma polymerization of acrylic acid (AA), not only the chemical structure and film thickness of the deposits were studied, but also a new way to obtain COOH-rich surfaces. This is an important aspect when applying the obtained coatings for biomedical and electronics applications. Therefore, acrylic acid/CO2 polymer films with a thickness of ca. 150 nm were deposited in the pulsed plasma regime onto polyethylene and aluminium as organic and inorganic substrates. Their structure–property relationships were studied in dependence on the mixture ratio of acrylic acid monomer and CO2 gas. The influence of the CO2 gas on the regularity and functionality of plasma deposited poly(acrylic acid) (PAA) was studied in detail using bulk-sensitive (dielectric spectroscopy and Fourier transforms infrared spectroscopy) as well as surface-sensitive methods such as X-ray photoelectron spectroscopy. For a clear identification of the functionality of the deposited films, the COOH groups were estimated after derivatization with trifluoroethanol by XPS measurement as well as by the quantitative analysis of the FTIR data. Results show, in presence of a small amount of CO2 gas within the acrylic acid plasma, a structure of poly(acrylic acid) with high concentration of COOH groups was obtained. However, the excess of CO2 gas in the plasma chamber leads to fragmentation of the monomer or/and degradation of the layer which is already deposited. A polymer network is obtained with an increasing abundance of branched groups for AA/CO2 with increasing CO2 gas in the mixture. KW - Poly(acrylic acid) KW - Plasma polymerization KW - COOH rich surfaces PY - 2016 DO - https://doi.org/10.1002/ppap.201500128 SN - 1612-8850 VL - 13 IS - 5 SP - 499 EP - 508 PB - Wiley-VCH Verlag CY - Weinheim AN - OPUS4-36058 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Schönhals, Andreas T1 - Influence of a nanoscale confinement on the dynamics of discotic liquid crystals investigated by inelastic neutron scattering and relaxation spectroscopy N2 - Discotic liquid crystals (DLCs) are self-assembled materials where self-assembly is driven by non-covalent intermolecular interactions. The corresponding molecules consist of a flat and rigid aromatic core substituted by flexible aliphatic side chains. While the former is responsible for the π-stacking, the latter gives rise to an increased solubility, processability, and rich thermotropic behavior. The disc-shaped molecules form columns that further assemble into two-dimensional arrays with a hexagonal mesophase. The alkyl chains fill the intracolumnar space giving rise to a nanophase separated state. Two different homologous systems based on triphenylene derivatives were investigated as model systems for DCLs where the length of the aliphatic side chains is widely varied. Measurements were carried out in the bulk state and confined to the nanometre wide channels of anodic aluminum membranes (Pore diameter 20 nm, 40nm, 80 nm and 180 nm) by means of inelastic and quasielastic neutron scattering. These investigations were accompanied by calorimetry and dielectric relaxation spectroscopy. From the neutron scattering experiments the vibrational density of states (Boson Peak) from neutron time-of-flight spectroscopy, the molecular dynamics on a time scale of ca. 1 ns (elastic scans from neutron backscattering spectrometers) as well as quasielastic neutron scattering by a combination of time-of-flight spectroscopy and backscattering were considered. Structural information is retrieved by X-ray diffraction carried out on a synchrotron. The dynamics of these unique soft matter materials are discussed in detail considering their structure (length of the aliphatic side chain), the effect of self-confinement (of the aliphatic chains in the intracolumnar space) and of outer confinement (influence of the pore size). Comparison is further made to pyrene based system. T2 - 18. International Seminar on Neutron Scattering Investigations in Condensed Matter CY - Poznan, Poland DA - 12.05.2016 KW - Discotic liquid crystals KW - Nanoconfinement KW - Neutron scattering PY - 2016 AN - OPUS4-36059 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Madkour, Sherif A1 - Melnichu, I. A1 - Choukourov, A. A1 - Krakovsky, I. A1 - Biedermann, H. A1 - Schönhals, Andreas T1 - In situ nanocalorimetric investigations of plasma assisted deposited poly(ethylene oxide)-like films by specific heat spectroscopy N2 - In the recent years, highly crosslinked plasma polymers have started to unveil their potential in numerous biomedical applications in thin-films form. However, conventional diagnostic methods often fail due to their diverse molecular dynamics conformations. Here, glassy dynamics and the melting transition of thin PEO-like plasma assisted deposited (ppPEO) films (thickness 100 nm) were In situ studied by a combination of specific heat spectroscopy, utilizing pJ/K sensitive AC-calorimeter chip, and composition analytical techniques. Different crosslinking densities were obtained by different plasma powers during the deposition of the films. Glassy dynamics was observed for all values of the plasma power. It was found that the glassy dynamics slows down with increasing the plasma power. Moreover, the underlying relaxation time spectra broaden indicating that the molecular motions become more heterogeneous with increasing plasma power. In a second set of experiment, the melting behavior of the ppPEO films was studied. The melting temperature of ppPEO was found to be decreasing with increasing plasma power. This was explained by a decrease of the order in the crystals due to formation of chemical defects during the plasma process. KW - Plasma deposited polymers KW - Nanocalorimetry KW - Thin polymer films KW - Glass transition PY - 2016 DO - https://doi.org/10.1021/acs.jpcb.6b01355 SN - 1520-6106 SN - 1520-5207 VL - 120 IS - 16 SP - 3954 EP - 3962 PB - American Chemical Society CY - Washington, DC, USA AN - OPUS4-35922 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Frunza, S. A1 - Frunza, L. A1 - Ganea, C. P. A1 - Zgura, I. A1 - Bras, A. R. A1 - Schönhals, Andreas T1 - Rod-like cyanophenyl probe molecules nanoconfined to oxide particles: Density of adsorbed surface species N2 - Surface layers have already been observed by broadband dielectric spectroscopy for Composite systems formed by adsorption of rod-like cyanophenyl derivates as probe molecules on the surface of oxide particles. In this work, features of the surface layer are reported; samples with different amounts of the probe molecules adsorbed onto oxide (nano) particles were prepared in order to study their interactions with the surface. Thermogravimetric analysis (TGA) was applied to analyze the amount of loaded probe molecules. The density of the surface species ns was introduced and its values were estimated from quantitative Fourier transform infrared spectroscopy (FTIR) coupled with TGA. This parameter allows discriminating the composites into several groups assuming a similar interaction of the probe molecules with the hosts of a given group. An influence factor H is further proposed as the ratio of the number of molecules in the surface layer showing a glassy dynamics and the number of molecules adsorbed tightly on the surface of the support: It was found for aerosil composites and used for calculating the maximum filling degree of partially filled silica MCM-41 composites showing only one dielectric process characteristic for glass-forming liquids and a bulk behavior for higher filling degrees. KW - Cyanophenyl molecules KW - Nanoconfinement KW - Surface Species PY - 2016 DO - https://doi.org/10.1140/epjp/i2016-16027-5 SN - 2190-5444 VL - 131:27 IS - 2 SP - 1 EP - 9 PB - Springer AN - OPUS4-35364 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Yin, Huajie A1 - Madkour, Sherif Aly Hassan Aly A1 - Schönhals, Andreas T1 - Unambiguous evidence for a highly mobile surface layer in ultrathin polymer films by specific heat spectroscopy on blends N2 - Despite the decade long controversial discussion on the effect of nanometer confinement on the glass transition temperature (Tg) of ultrathin polymer films, there is still no consistent picture. Here, the dynamic calorimetric glass transition of ultrathin films of a blend, which is miscible in the bulk, is directly investigated by specific heat spectroscopy. By a self-assembling process, a nanometer thick surface layer with a higher molecular mobility is formed at the polymer/air interface. By measuring the dynamic calorimetric Tg in dependence on the film thickness, it was shown that the Tg of the whole film was strongly influenced by that nanometer thick surface layer, with a lower Tg. Since the observed thickness dependence of the dynamic Tg is similar to the thickness dependence of the Tg for thin films of homopolymers, it is concluded that also for homopolymer a highly mobile surface layer is relevant for the widely observed Tg depression. PY - 2015 DO - https://doi.org/10.1021/acs.macromol.5b01259 SN - 0024-9297 SN - 1520-5835 VL - 48 IS - 14 SP - 4936 EP - 4941 PB - American Chemical Society CY - Washington, DC AN - OPUS4-33841 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Füllbrandt, Marieke A1 - Ermilova, E. A1 - Asadujjaman, Asad A1 - Hölzel, R. A1 - Bier, F.F. A1 - Von Klitzing, R. A1 - Schönhals, Andreas T1 - Dynamics of linear poly(N-isopropylacrylamide) in water around the phase transition investigated by dielectric relaxation spectroscopy N2 - The molecular dynamics of linear poly(N-isopropylacrylamide) (pNIPAM) in aqueous media at temperatures below and above the lower critical solution temperature (LCST) are investigated using broadband dielectric relaxation spectroscopy in a frequency range from 10–1 to 1011 Hz. Below the LCST, two relaxation processes are observed in the megahertz and gigahertz region assigned to the reorientation of dipoles of the solvated polymer segments (p-process) and water molecules (w-process), respectively. Both relaxation processes are analyzed using the Havriliak–Negami (HN) function, taking special attention to the w-process. Above the LCST, the dielectric spectra of the pNIPAM solutions resemble that of pure water, showing only the high frequency relaxation process of the water molecules with a more or less Debye-type behavior. The non-Debye behavior of the w-process below the LCST is mainly induced by the interactions between water and pNIPAM chains via hydrogen bonding. The relaxation time and strength of the w-process is studied with dependence on the concentration, temperature, and the polymer chain length (molecular weight). The information obtained is useful for a deeper understanding of the dehydration behavior at the phase transition. The suggestion of dehydration of the pNIPAM chains at the LCST is confirmed by calculating a dehydration number. PY - 2014 DO - https://doi.org/10.1021/jp501325x SN - 1520-6106 SN - 1520-5207 SN - 1089-5647 VL - 118 IS - 13 SP - 3750 EP - 3759 PB - Soc. CY - Washington, DC AN - OPUS4-30578 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Yildirim, Arda A1 - Kolmangadi, Mohamed Aejaz A1 - Bühlmeyer, A. A1 - Huber, P. A1 - Laschat, S. A1 - Schönhals, Andreas T1 - Electrical conductivity and multiple glassy dynamics of crow-ether based columnar liquid crystals N2 - The phase behavior of two unsymmetrical triphenylene crown ether-based columnar liquid crystals (CLCs) bearing different lengths of alkyl chains, KAL465 and KAL468, was investigated using differential scanning calorimetry (DSC). A plastic crystalline (Cry), columnar liquid crystalline (Colh) and an isotropic phase were observed along with two glass transitions in the Cry phase. The molecular mobility of the KAL compounds was further studied by a combination of broadband dielectric spectroscopy (BDS) and advanced calorimetric techniques. By the BDS investigations, three dielectric active relaxation processes were observed for both samples. At low temperatures, a γ-process in the Cry state was detected and is assigned to the localized fluctuations taking place in the alkyl chains. An α2-process takes place at higher temperatures in the Cry phase. An α3 process was found in the Colh mesophase. The advanced calorimetric techniques consist of fast scanning calorimetry (FSC) and specific heat spectroscopy (SHS) employing temperature modulated DSC and FSC (TMDSC and TMFSC). The advanced calorimetric investigations revealed that besides the α2 process in agreement with BDS, a second dynamic glass transition (α1-process) is present which is not observed by dielectric spectroscopy. The results are in good agreement with the glass transitions detected by DSC for this process. The temperature dependences of the relaxation rates of the α1 , α2 and α3 processes are all different. Therefore, different molecular assignments for the relaxation processes are proposed. In addition to the relaxation processes, a conductivity contribution was explored by BDS for both KAL compounds. The conductivity contribution appears in both Cry and Colh phases, where the conductivity increases by ca. one order of magnitude at phase transition from the crystalline to the hexagonal phase. KW - Columnar Liquid Crystal PY - 2020 DO - https://doi.org/10.1021/acs.jpcb.0c06854 VL - 124 IS - 39 SP - 8728 EP - 8739 PB - ACS AN - OPUS4-51374 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Schönhals, Andreas T1 - Thermal behavior of high preformance polymers - Fast Scanning Calorimetry and more N2 - The glass tranistion behavior of polymers of intrinsic microporosity and polynornornes is discussed. T2 - Flash DSC Conference 2021 CY - Online meeting DA - 06.12.2021 KW - Polymer of Intrisic Maicroporosity KW - Highly permeable polynorbornenes PY - 2021 AN - OPUS4-53938 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Fahmy, Alaa A1 - Saied, M. A. A. A1 - Morgan, N. A1 - Abdelbary, H. A1 - Bahy, S. M. A1 - Schönhals, Andreas A1 - Friedrich, J. F. T1 - Modified polyvinyl chloride membrane grafted with an ultra-thin polystyrene film: structure and electrochemical properties N2 - The work explores the synthesis and the properties of a novel composite membrane System based on modified polystyrene (PS) grafted onto a polyvinyl chloride (PVC) membrane. PVC membranes were prepared by solution-casting followed by exposure to an atmospheric pressure dielectric barrier discharge (DBD) with O2 to obtain an activated Surface for grafting PS to it. Moreover, the thus prepared membranes were chemically modified furthermore by amination with polyethyleneimine or sulfonation with 4 M sulfuric acid. The membrane surface characteristics such as wettability, structure and morphology were investigated using water contact angle measurements, attenuated total reflection Fourier transform infrared spectroscopy and scanning electron microscopy experiments. The thermogravimetric stability and electrolytic responses of the membranes were studied utilizing TGA, ion exchange capacity (IEC), and solvent uptake. A significant result of plasma and chemical modification was to produce a membrane material with low permeability. Thus, the methanol permeability of the sulfonated membranes measured for 12 h was measured to 2.34$10� 8 cm2 s� 1 compared to 177.00$10� 8 cm2 s� 1 of Nafion 117®which is considered as a benchmark. This result indicates that the prepared sulfonated samples are an innovative and effective material for decreasing the methanol crossover in fuel cells to a great extent. This makes the PVC-g-St membranes are promising and attractive as new materials for polyelectrolyte membrane for fuel cells. KW - Electrolyte membrane KW - Fuell cells PY - 2021 UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-526794 DO - https://doi.org/10.1016/j.jmrt.2021.04.018 VL - 12 SP - 2273 EP - 2284 PB - Elsevier B.V. AN - OPUS4-52679 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Kolmangadi, Mohamed Aejaz A1 - Yildirim, Arda A1 - Sentker, K. A1 - Butschies, M. A1 - Bühlmeyer, A. A1 - Huber, P. A1 - Lachat, S. A1 - Schönhals, Andreas T1 - Molecular dynamics and electrical conductivity of Guanidinium based Ionic liquid crystals: Influence of cation headgroup configuration N2 - Molecular mobility and conductivity of four bent shaped tetramethylated guanidinium based ionic liquid crystals (ILCs) with varying head group configuration (cyclic or acyclic) and alkyl chain length is investigated by a combination of broadband dielectric spectroscopy (BDS) and specific heat spectroscopy (SHS). Two dielectrically active processes observed in the plastic crystalline phase at low and high temperatures are denoted as γ and α1 relaxation. The former is assigned to localized fluctuations of methyl groups including nitrogen atoms in the guanidinium head groups. SHS investigations reveal one calorimetrically active process termed as α2 relaxation process. The temperature dependencies of the relaxation rates of α1 and α2 are similar for the cyclic ILC while for the acyclic counterpart they are different. Possible molecular assignments for the α1 and α2 relaxation are discussed in detail. Alongside relaxation processes, a significant conductivity contribution was observed for all ILCs, where the absolute value of DC conductivity increases by 4 orders of magnitude at the transition from the crystalline to the hexagonal columnar phase. The increase is traced to the change in the underlying conduction mechanism from the delocalized electrical conduction in the Cry phase to ionic conduction in the quasi 1D ion columns formed in the hexagonal columnar mesophase. KW - Ionic liquid crystal PY - 2021 DO - https://doi.org/10.1016/j.molliq.2021.115666 VL - 330 SP - 115666 PB - Elsevier B.V. AN - OPUS4-52284 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Szymoniak, Paulina A1 - Qu, Xintong A1 - Abbasi, M. A1 - Pauw, Brian Richard A1 - Henning, S. A1 - Li, Z. A1 - Wang, D.-Y. A1 - Schick, C. A1 - Saalwächter, K. A1 - Schönhals, Andreas T1 - Spatial inhomogeneity, Interfaces and Complex Vitrification Kinetics in a Network Forming Nanocomposite N2 - A detailed calorimetric study on an epoxy-based nanocomposite system was performed employing bisphenol A diglycidyl ether (DGEBA) cured with diethylenetriamine (DETA) as the polymer matrix and taurine-modified MgAL layered double hydroxide (T-LDH) as nanofiller. The -NH2 group of taurine can react with DGEBA improving the interaction of the polymer with the filler. The combined X-ray scattering, and electron microscopy data showed that the nanocomposite has a partially exfoliated morphology. Calorimetric studies were performed with conventional DSC, temperature modulated DSC (TMDSC) and fast scanning calorimetry (FSC) in the temperature modulated approach (TMFSC) to investigate the vitrification and molecular mobility in dependence of the filler concentration. First, TMDSC and NMR were used to estimate the amount of the rigid amorphous fraction which consists of immobilized polymer segments at the nanoparticle surface. It was found to be 40 wt% for the highest filler concentration, indicating that the interface dominates the overall macroscopic properties and behavior of the material to a great extent. Second, the relaxation rates of the α-relaxation obtained by TMDSC and TMFSC were compared with the thermal and dielectric relaxation rates measured by static FSC. The investigation revealed that the system shows two distinct α-relaxation processes. Furthermore, also two separate vitrification mechanisms were found for a bulk network-former without geometrical confinement as also confirmed by NMR. This was discussed in terms of the intrinsic spatial heterogeneity on a molecular scale, which becomes more pronounced with increasing nanofiller content. KW - Polymer based Nanocomposites PY - 2021 UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-523199 DO - https://doi.org/10.1039/d0sm01992e SN - 1744-6848 VL - 17 IS - 10 SP - 2775 EP - 2790 PB - Royal Society of Chemistry AN - OPUS4-52319 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Knelles, J. A1 - Wanner, C. A1 - Schulz, F. A1 - Freund, M. A1 - Kolmangadi, Mohamed Aejaz A1 - Baro, A. A1 - Huber, P. A1 - Schönhals, Andreas A1 - Lachat, S. T1 - Liquid crystalline hydrazones revisited: dipolar interactions vs hydrogen bonding affecting mesomorphic properties N2 - In order to understand the role of dipolar interactions vs. H-bonding, a series of hydrazones were synthesised from 4-alkoxy-, 3,4-dialkoxy- or 3,4,5-trialkoxybenzaldehydes and phenyl, bromo- or nitrophenylhydrazine, respectively. Their mesomorphic properties were investigated by differential scanning calorimetry (DSC), polarising optical microscopy (POM), X-ray diffraction (WAXS, SAXS) and compared with known members. Only those hydrazones derived from 3,4,5-trisalkoxybenzaldehyde and either meta, meta-dinitro- or ortho, para-dinitrophenylhydrazine displayed hexagonal columnar mesophases. All other derivatives were non-mesomorphic, even when H-bonds were present. Dipole moments of the various nitro-substituted hydrazones were experimentally determined by dielectric measurements and supported by theoretical DFT calculations, which indicated that the mesophase formation is mostly governed by strong dipole moment and further enforced by intramolecular H-bonding. KW - Discotic liquid crystals PY - 2021 DO - https://doi.org/10.1080/02678292.2021.1873438 VL - 48 IS - 10 SP - 1382 EP - 1391 PB - Taylor & Francis AN - OPUS4-52409 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Fahmy, Alaa A1 - Kolmangadi, Mohamed Aejaz A1 - Schönhals, Andreas A1 - Friedrich, J. T1 - Structure of plasma‐deposited copolymer films preparedfrom acrylic acid and styrene: Part III sulfonation andelectrochemical properties N2 - Acrylic acid-styrene copolymer films were deposited plasma-chemically more gently using the pulsed plasma mode instead of the continuous mode, with linear and some slightly branched chains and marginal crosslinking. Then, the styrene unit of copolymers was wet-chemically sulfonated by chlorosulfuric acid. On exposure to air, the formed 4-chlorosulfonic acid groups hydrolyze to sulfonic acid groups (-SO3H). FTIR, XPS and broadband dielectric spectroscopy were employed to characterize the composition, the structure, the functional groups, and the electrochemical performance for the copolymers. A high concentration of sulfonic acid-containing groups was obtained in the sulfonated PS sample. The values of the DC conductivity DC for the sulfonated sample of the AA/S copolymer are ca. five orders of magnitude higher than that of the not-sulfonated copolymer materials. KW - Plasma Polymers KW - Electrolyte membrane PY - 2022 DO - https://doi.org/10.1002/ppap.202100222 SP - 1 EP - 12 PB - Wiley VHC-Verlag AN - OPUS4-54539 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Yildirim, Arda A1 - Krause, Christina A1 - Huber, P. A1 - Schönhals, Andreas T1 - Multiple glassy dynamics of a homologous series of triphenylene-based columnar liquid crystals – A study by broadband dielectric spectroscopy and advanced calorimetry N2 - Hexakis(n-alkyloxy)triphenylene) (HATn) consisting of an aromatic triphenylene core and alkyl side chains are model discotic liquid crystal (DLC) systems forming a columnar mesophase. In the mesophase, the molecules of HATn self-assemble in columns, which has one-dimensional high charge carrier mobility along the columns. Here, a homologous series of HATn with different length of the alkyl chain (n = 5,6,8,10,12) is investigated using differential scanning calorimetry (DSC), broadband dielectric spectroscopy (BDS) and advanced calorimetric techniques including fast scanning calorimetry (FSC) and specific heat spectroscopy (SHS). The investigation of the phase behavior was done utilizing DSC experiments and the influence of the alkyl chain length on the phase behavior was revealed. By the dielectric investigations probing the molecular mobility, a c-relaxation due to localized fluctuations as well as two glassy dynamics, the acore- and aalkyl-relaxation, were observed in the temperature range of the plastic crystalline phase. Moreover, the observed glassy dynamics were further studied employing advanced calorimetry. All observed relaxation processes are attributed to the possible specific molecular fluctuations and discussed in detail. From the results a transition at around n = 8 from a rigid constrained (n = 5,6) to a softer system (n = 10,12) was revealed with increasing alkyl chain length. A counterbalance of two competing effects of a polyethylene-like behavior of the alkyl chains in the intercolumnar domains and self-organized confinement is discussed in the context of a hindered glass transition. KW - Discotic liquid crystals KW - Broadband dielectric spectroscopy KW - Advanced calorimetry PY - 2022 DO - https://doi.org/10.1016/j.molliq.2022.119212 VL - 358 SP - 1 EP - 10 PB - Elsevier B.V. AN - OPUS4-54721 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Frunza, L. A1 - Zgura, I A1 - Ganea, C. P. A1 - Schönhals, Andreas T1 - Molecular dynamics of alkyl benzoate liquid crystals in the bulk state and in the surface layer of their composites with oxide nanopowders N2 - This paper presents the results concerning monotropic nematic liquid crystals 4-pentylphenyl 40-alkyl benzoate (5PnB) (n = 3 or 5 carbon atoms in the alkyl chain). Their mesophase properties were supported by images of the polarized optical microscopy. Molecular dynamics in the bulk samples or in the composites prepared with aerosil A380 was investigated by broadband dielectric spectroscopy in a large temperature range, appropriately chosen. Thermo gravimetric and infrared investigations were additionally performed. The data were compared with those of structurally related nematics like cyanophenyl pentyl benzoates, which have a cyan group instead of the pentyl chain. The dielectric spectra of the bulk 3P5B and 5P5B demonstrate a dielectric behavior with several relaxation processes as expected for nematic liquid crystals. The temperature dependence of the relaxation rates (and of the dielectric strength) seems to have two distinguished regimes. Thus, in the isotropic state, at higher temperatures the data obey the Vogel–Fulcher–Tammann law, whereas an Arrhenius law is fitted at lower temperature, in a close similarity to the behavior of a constrained dynamic glass transition. Samples with a high density of silica (larger than 7 g aerosil/1 g of 5PnB) were prepared to observe a thin layer adsorbed on the particle surface; it was estimated that almost each guest 5PnB molecule interacts with the aerosil surface. For the composites only one main relaxation process is observed at frequencies much lower than those for the corresponding bulk, which was assigned to the dynamics of the molecules in the surface layer. Infrared spectroscopy shows that these molecules interact with the surface by the ester carbonyl group leading to the monolayer self-assembly at liquid–solid interface. We note once more the importance of the functional unit(s) for the interaction with the hydroxyl groups on the aerosil surface. KW - Liquid crystals PY - 2022 DO - https://doi.org/10.1016/j.molliq.2022.119374 SN - 0167-7322 VL - 359 SP - 1 EP - 11 PB - Elsevier B.V. AN - OPUS4-54867 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Schönhals, Andreas T1 - Multiple glassy dynamics of a homologous series of triphenylene-based columnar liquid crystals – A study by broadband dielectric spectroscopy, advanced calorimetry and Neutron Scattering N2 - Hexakis(n-alkyloxy)triphenylene) (HATn) consisting of an aromatic triphenylene core and alkyl side chains are model discotic liquid crystal (DLC) systems forming a columnar mesophase. In the mesophase, the molecules of HATn self-assemble in columns, which has one-dimensional high charge carrier mobility along the columns. Here, a homologous series of HATn with different length of the alkyl chain (n=5,6,8,10,12) is investigated using differential scanning calorimetry (DSC), broadband dielectric spectroscopy (BDS) and advanced calorimetric techniques including fast scanning calorimetry (FSC) and specific heat spectroscopy (SHS). The investigation of the phase behavior was done utilizing DSC experiments and the influence of the alkyl chain length on the phase behavior was revealed. By the dielectric investigations probing the molecular mobility, a γ-relaxation due to localized fluctuations as well as two glassy dynamics the αcore and αalkyl relaxation were observed in the temperature range of the plastic crystalline phase. Moreover, the observed glassy dynamics were further studied employing advanced calorimetry. All observed relaxation processes are attributed to the possible specific molecular fluctuations and discussed in detail. From the results a transition at around n=8 from a rigid constrained (n=5,6) to a softer system (n=10,12) on a molecular lenght scale was revealed with increasing alkyl chain length. A counterbalance of two competing effects of a polyethylene like behavior of the alkyl chains in the intercolumnar domains and self-organized confinement is discussed in the context of a hindered glass transition. T2 - 11th Conferenz on Broadband Dielectric Spectroscopy and its Applications CY - San Sebastian, Spain DA - 04.09.2022 KW - Discotic Liquid Crystals PY - 2022 AN - OPUS4-55672 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Schönhals, Andreas T1 - Inelastic and Quasielastic Neutron Scattering Experiments on Mircroporous Membranes for Green Separation processes N2 - Polymers with intrinsic microporosity are promising candidates for the active separation layer in gas separation membranes. These polymers are characterized by a high permeability and reasonable permselectivity. The reasonable permselectivity of these materials is somehow surprising because for microporous systems a more Knudsen-like diffusion is expected rather than a size dependent temperature activated sieving process. It was argued in the framework of a random gate model that molecular fluctuations on a time scale from ps to ns are responsible for the permselectivity. Here a series of microporous polynorbornenes with bulky SiMe3 side groups and a rigid backbone is considered which have different microporosities characterized by BET surface area values. First inelastic time-of-flight neutron scattering measurements were carried out to investigate the low frequency density of state (VDOS). The measured data show the characteristic low frequency excess contribution to the VDOS above the Debye sound wave level, generally known as the Boson peak in glass-forming materials. It was found that the maximum position of the Boson peak correlates with the BET surface area. For two selected comparable polynorbornenes elastic scans as well as QENS measurements by a combination of neutron time-of-flight and backscattering were carried out. A low temperature relaxation process was found for both polymers. This process was assigned to the methyl group rotation. It was analysed in terms of a jump diffusion in a three-fold potential. The analysis of the dependence of the elastic incoherent structure factor on the scattering vector yields the number of methyl groups which might be immobilized. T2 - QENS / WINS 2022 CY - San Sebastian, Spain DA - 23.05.2022 KW - Polymers of intrinsic Microporosity PY - 2022 AN - OPUS4-55673 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Schönhals, Andreas T1 - Inelastic and Quasielastic Neutron Scattering Experiments on Mircroporous Membranes for Green Separation processes N2 - Polymers with intrinsic microporosity are promising candidates for the active separation layer in gas separation membranes. These polymers are characterized by a high permeability and reasonable permselectivity. The latter point is somehow surprising because for microporous systems a more Knudson-like diffusion is expected then a size dependent temperature activated sieving process. It was argued in the framework of a random gate model that molecular fluctuations on a time scale from ps to ns are responsible for the permselectivity. Her a series of microporous polynorbornenes with bulky Si side groups and a rigid backbone are considered which have different microporosity characterized by BET surface area values. First inelastic time-of-flight neutron scattering measurements were carried out to investigate the low frequency density of state (VDOS). The measured data show the characteristic low frequency excess contribution to the VDOS above the Debye sound wave level, generally known as the Boson peak in glass-forming materials. It was found the maximum position of the Boson peak correlates with the BET surface area value. For two selected comparable polynorbornenes elastic scans as well as QENS measurements by a combination of neutron time-of-flight and backscattering are carried out. A low temperature relaxation process was found for both polymers. This process was assigned to the methyl group rotation. It was analysed in terms of a jump diffusion in a three-fold potential. The analysis of the dependence of the elastic incoherent structure factor on the scattering vector yields the number of methyl groups which might be immobilized. T2 - MLZ Conference 2022: Neutrons for mobility CY - Lengries, Germany DA - 31.05.2022 KW - Polymers of intrinsic Microporosity PY - 2022 AN - OPUS4-55674 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Grunwald, M. A. A1 - Hagenlocher, S. E. A1 - Turkanovic, L. A1 - Bauch, S. M. A1 - Wachsmann, S. B. A1 - Altevogt, L. A. A1 - Ebert, M. A1 - Knöller, J. A. A1 - Raab, A. R. A1 - Schulz, F. A1 - Kolmangadi, Mohamed A. A1 - Zens, A. A1 - Huber, P. A1 - Schönhals, Andreas A1 - Bilitiewski, U. A1 - Laschat, S. T1 - Does thermotropic liquid crystalline self-assembly control biological activity in amphiphilic amino acids? – tyrosine ILCs as a case study N2 - Amphiphilic amino acids represent promising scaffolds for biologically active soft matter. In order to understand the bulk self-assembly of amphiphilic amino acids into thermotropic liquid crystalline phases and their biological properties a series of tyrosine ionic liquid crystals (ILCs) was synthesized, carrying a benzoate unit with 0–3 alkoxy chains at the tyrosine unit and a cationic guanidinium head group. Investigation of the mesomorphic properties by polarizing optical microscopy (POM), differential scanning calorimetry (DSC) and X-ray diffraction (WAXS, SAXS) revealed smectic A bilayers (SmAd) for ILCs with 4-alkoxy- and 3,4-dialkoxybenzoates, whereas ILCs with 3,4,5-trisalkoxybenzoates showed hexagonal columnar mesophases (Colh ), while different counterions had only a minor influence. Dielectric measurements revealed a slightly higher dipole moment of non-mesomorphic tyrosine-benzoates as compared to their mesomorphic counterparts. The absence of lipophilic side chains on the benzoate unit was important for the biological activity. Thus, non-mesomorphic tyrosine benzoates and crown ether benzoates devoid of additional side chains at the benzoate unit displayed the highest cytotoxicities (against L929 mouse fibroblast cell line) and antimicrobial activity (against Escherichia coli DTolC and Staphylococcus aureus) and promising selectivity ratio in favour of antimicrobial activity. KW - Liquid Crystals PY - 2023 DO - https://doi.org/10.1039/d3cp00485f SN - 1463-9076 VL - 25 IS - 26 SP - 17639 EP - 17656 PB - RCS AN - OPUS4-57796 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Fahmy, Alaa A1 - Omar, Hassan A1 - Szymoniak, Paulina A1 - Schönhals, Andreas A1 - Friedrich, J. T1 - Structure of plasma deposited acrylic acid‐allyl alcohol copolymers N2 - Copolymer thin films with two types of functional groups have excellent performance as sensors, for example. The formation and deposition of allyl alcohol‐acrylic acid copolymer films by pulsed high frequency plasma is a complex process. As usual, the chemical composition of the top surface of the films was investigated by XPS and FTIR measurements. Furthermore, contact angle measurements with water were used to characterise the hydrophilicity and wettability of the polymer films. After plasma deposition, a significant decrease in functional groups (OH and COOH) was observed compared to the classically copolymerised equivalent. The remaining functional groups, i.e. the majority of these groups, were sufficient for application as sensor layers. Segmental mobility and conductivity, important for sensor applications, were analysed by broadband dielectric spectroscopy. KW - Plasma Polymerization PY - 2023 UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-578349 DO - https://doi.org/10.1002/ppap.202300071 SN - 1612-8850 SP - 1 EP - 14 PB - Wiley online library AN - OPUS4-57834 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Yildirim, Arda A1 - Krause, Christina A1 - Zorn, R. A1 - Schönhals, Andreas T1 - Multiple glassy dynamics of a homologous series of triphenylene-based columnar liquid crystals – A study by broadband dielectric spectroscopy, advanced calorimetry and Neutron Scattering N2 - Hexakis(n-alkyloxy)triphenylene) (HATn) consisting of an aromatic triphenylene core and alkyl side chains are model discotic liquid crystal (DLC) systems forming a columnar mesophase. In the mesophase, the molecules of HATn self-assemble in columns, which has one-dimensional high charge carrier mobility along the columns. Here, a homologous series of HATn with different length of the alkyl chain (n=5,6,8,10,12) is investigated using differential scanning calorimetry (DSC), broadband dielectric spectroscopy (BDS) and advanced calorimetric techniques including fast scanning calorimetry (FSC) and specific heat spectroscopy (SHS). The investigation of the phase behavior was done utilizing DSC experiments and the influence of the alkyl chain length on the phase behavior was revealed. By the dielectric investigations a γ-relaxation due to localized fluctuations as well as two glassy dynamics the αcore and αalkyl relaxation were observed in the temperature range of the plastic crystalline phase. Moreover, the observed glassy dynamics were further studied employing advanced calorimetry. All observed relaxation processes are attributed to the possible specific molecular fluctuations and discussed in detail. From the results a transition at around n=8 from a rigid constrained (n=5,6) to a softer system (n=10,12) on a molecular lenght scale was revealed with increasing alkyl chain length. A counterbalance of two competing effects of a polyethylene like behavior of the alkyl chains in the intercolumnar domains and self-organized confinement is discussed in the context of a hindered glass transition. The results were confirmed by in- and quasielastic neutron scattering T2 - Confit 2022 CY - Grenoble, France DA - 10.10.2022 KW - Glassy Dynamics KW - Discotic Liquid Crystals PY - 2022 AN - OPUS4-56661 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Kolmangadi, Mohamed A. A1 - Wani, Y. M. A1 - Schönhals, Andreas A1 - Nikoubashman, A. T1 - Coarse-Grained Simulations of Columnar Ionic Liquid Crystals: Comparison with Experiments N2 - We simulate a homologous series of guanidinium-based columnar ionic liquid crystals (ILCs) using coarse-grained molecular dynamics (MD) simulations with the Martini force field. We systematically vary the length of alkyl side chains, ILC-n (n = 8, 12, 16), and compare our results with previous experimental findings. Experimentally, ILC-8 exhibits a narrow mesophase window and weak columnar order, while ILC-12 and ILC-16 display a broad mesophase window and high columnar order. The MD simulations show that ILC-8 forms a percolated structure, whereas the longer chain analogues self-assemble into columns, with columnar assembly becoming more prominent as the side chain length increases, in qualitative agreement with the experiments. Furthermore, the intercolumnar distance increases monotonically with increasing side chain length and decreases with increasing temperature. Finally, we find that the diffusion coefficient and ionic conductivity decrease substantially with increasing chain length, consistent with experimental observations. We attribute this decrease in mobility to the formation of hexagonally ordered columns, which restrict transport more than percolated networks. KW - Ionic liquid crystals PY - 2024 DO - https://doi.org/10.1021/acs.jpcb.4c03041 SN - 1520-6106 SP - 1 EP - 8 PB - ACS AN - OPUS4-60857 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Schönhals, Andreas A1 - Zorn, R. A1 - Frick, B. T1 - Inelastic neutron spectroscopy as a tool to investigate nanoconfined polymer systems N2 - The effect of a nanometer scale confinement (pore sizes 7.5 nm down to 2.5 nm) on the vibrational density of states (VDOS) and on the molecular dynamics of Poly(dimethyl siloxane) (PDMS) and Poly(-methyl phenyl siloxane) (PMPS) is studied by inelastic Neutron scattering. The high penetration depth of neutrons makes neutron scattering a suitable tool for the study of confined systems. Moreover, Neutrons are sensitive to light nuclei therefore the confined polymers can be investigated directly, more or less independently of the confining host. Resulting findings are firstly, a reduction of the low frequency contributions to the VDOS below the Boson Peak frequency for both polymers. Including literature data, this reduction can be regarded as a more general feature for glass-forming systems confined by hard walls. Secondly, clear deviations in the temperature dependence of the mean squared displacement of the confined molecules compared to the bulk were found close to the thermal glass transition temperature, whereas localized methyl group rotations were only weakly influenced. Furthermore, the molecular dynamics is accessed. The combination of neutron Time-of-Flight with neutron backscattering, thus covering a broad dynamical range from sub ps to ns, reveal clear influence from confinement on the intermediate incoherent scattering function S(q,t). The latter was obtained by combining the inverse Fourier transform of the individual dynamical structure factors measured by the both methods. The time and q dependence of S(q,t) are discussed in detail for the local methyl group rotations and the segmental dynamics, considering both the interaction of the segments with the pore walls and possible geometrical confinement effects. KW - Confinement KW - Density of states KW - Dynamic glass transition PY - 2016 DO - https://doi.org/10.1016/j.polymer.2016.06.006 SN - 0032-3861 SN - 1873-2291 VL - 105 SP - 393 EP - 406 PB - Elsevier AN - OPUS4-38256 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Schönhals, Andreas T1 - Broadband dielectric spectroscopy as an orthogonal tool to mechanical analysis – From theory to applications N2 - The basics of broadband dielectric spectroscopy were introduced in detail. The analysis of the data was discussed. As application of broadband dielectric spectroscopy the alpha-relaxation (dynamic glass transition), the chain dynamics of polymers, and the behavior of a high performance polymer were illustrated. T2 - Geesthachter Polymertage CY - Geesthcht, Germany DA - 08.11.2016 KW - Broadband dielectric spectroscopy PY - 2016 AN - OPUS4-38185 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Schönhals, Andreas T1 - Broadband Dielectric Spectroscopy - Basics and Selected Applications N2 - The basics of broadband dielectric spectroscopy were introduced in detail. The analysis of the data was discussed. As application of broadband dielectric spectroscopy the alpha-relaxation (dynamic glass transition) and the chain dynamics of polymers were ilustrated. T2 - 9th International Conference on Broadband Dielectric Spectroscopy and its Applications CY - Pisa, Italy DA - 11.09.2016 KW - Broadband Dielectric Spectroscopy PY - 2016 AN - OPUS4-37386 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Schönhals, Andreas T1 - Behavior of Ultra-Thin Films of Blends of Polystyrene/ Poly(vinyl methyl ether) by Nanosized Relaxation Spectroscopy N2 - In the course of miniaturizing modern technology down to the molecular scale, understanding the materials behavior has to be investigated and deviations from the bulk that might arises from confinement effects has to be understood. Here, a combination of nano-sized relaxation spectroscopies (Broadband dielectric spectroscopy (BDS) and Specific heat spectroscopy (SHS); employing AC nanochip calorimetry) were utilized to investigate the glassy dynamics of ultra-thin films of blends of Poly (vinyl methyl ether) (PVME) / Polystyrene (PS) 50:50 wt-%, which are miscible bulk (thicknesses: 8nm - 200nm, film thickness was controlled by ellipsometry, film topography by AFM). Both methods are sensitive to different probes; where SHS senses entropy fluctuations while BDS measures dipole fluctuations. For BDS measurements, a recently developed nano-structured electrode sample arrangement is employed; where ultra-thin films are spin-coated on an ultra-flat highly conductive silicon wafer, sandwiched between a wafer with nanostructured SiO2 nano-spacers with heights between 35 nm and 70 nm. The method was applied for film thicknesses up to 50 nm. For thicker films, the samples were prepared between crossed electrodes. It was proven that, for 50 nm films, both contact methods will lead to identical results. By measuring the dynamic Tg in dependence of the film thickness, SHS showed that the Tg of the whole film was strongly influenced by a nanometer-thick surface layer at the polymer/air interface due to a self-assembling process [1]. The dynamic Tg obtained from the SHS measurements decrease with decreasing film thickness, evidencing the importance of a mobile surface layer at the polymer/air interface for the glass transition of the whole film. Compared to the SHS results, the BDS measurements show a completely different behavior. At high temperatures, the temperature dependence of the relaxation times of the films follows that of bulk-like PS/PVME; obeying the VFT-law. With decreasing temperature, the temperature dependence deviates from the VFT to an Arrhenius law; where the apparent activation energy decreases with decreasing film thickness. This is the first example where confinement induced changes were observed by BDS for ultra-thin films. All results were analyzed in details in a comprehensive discussion. T2 - 9th International Conference on Broadband Dielectric Spectroscopy and its Applications CY - Pisa, Italy DA - 11.09.2016 KW - Ultra-Thin films KW - Broadband Dielectric Spectrscopy KW - Nanostructured Electrodes PY - 2016 AN - OPUS4-37387 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Sentker, K. A1 - Zantop, A. W. A1 - Lippmann, M. A1 - Hofmann, T. A1 - Seeck, O. H. A1 - Kityk, A. V. A1 - Yildirim, Arda A1 - Schönhals, Andreas A1 - Mazza, M. G. A1 - Huber, P. T1 - Quantized self-assembly of discotic rings in a liquid crystal confined in nanopores N2 - Disklike molecules with aromatic cores spontaneously stack up in linear columns with high, onedimensional charge carrier mobilities along the columnar axes, making them prominent model systems for functional, self-organized matter.We show by high-resolution optical birefringence and synchrotron-based x-ray diffraction that confining a thermotropic discotic liquid crystal in cylindrical nanopores induces a quantized formation of annular layers consisting of concentric circular bent columns, unknown in the bulk state. Starting from the walls this ring self-assembly propagates layer by layer towards the pore center in the supercooled domain of the bulk isotropic-columnar transition and thus allows one to switch on and off reversibly single, nanosized rings through small temperature variations. By establishing a Gibbs free energy phase diagram we trace the phase transition quantization to the discreteness of the layers’ excess bend deformation energies in comparison to the thermal energy, even for this near room-temperature system. Monte Carlo simulations yielding spatially resolved nematic order parameters, density maps, and bondorientational order parameters corroborate the universality and robustness of the confinement-induced columnar ring formation as well as its quantized nature. KW - Discotic liquid crystals KW - Nanopores PY - 2018 UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-440253 DO - https://doi.org/10.1103/PhysRevLett.120.067801 SN - ‎0031-9007 SN - 1079-7114 VL - 120 IS - 6 SP - 067801-1 EP - 067801-7 PB - American Physical Society AN - OPUS4-44025 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Yildirim, Arda A1 - Szymoniak, Paulina A1 - Sentker, K. A1 - Butschies, M. A1 - Bühlmeyer, A. A1 - Huber, P. A1 - Laschat, S. A1 - Schönhals, Andreas T1 - Dynamics and ionic conductivity of ionic liquid crystals forming a hexagonal columnar mesophase N2 - For the first time, the molecular mobility of two linear-shaped tetramethylated guanidinium triflate ionic liquid crystals (ILCs) having different length of alkyl chains were investigated by a combination of broadband dielectric spectroscopy (BDS) and specific heat spectroscopy (SHS). By self-assembly, these ILCs can form a hexagonal ordered mesophase besides plastic crystalline phases and the isotropic state. Three dielectric active processes were found by BDS for both samples. At low temperatures, a γ-process in the plastic crystalline state is observed which is assigned to localized fluctuations of methyl groups including nitrogen atoms in the guanidinium head. At higher temperatures but still in the plastic crystalline state, an α1-process takes place. An α2 process was detected by SHS but with a completely different temperature dependence of the relaxation times than that of the α1-relaxation. This result is discussed in detail, and different molecular assignments of the processes are suggested. At even higher temperatures, electrical conductivity is detected and an increase in the DC conductivity by four orders of magnitude at the phase transition from the plastic crystalline to the hexagonal columnar mesophase is found. This result is traced to a change in the charge transport mechanism from a delocalized electron hopping in the stacked aromatic systems (in the plastic phase) to one dominated by an ionic conduction in the quasi-1D ion channels formed along the supermolecular columns in the ILCs hexagonal mesophases. KW - Ionic liquid crystalls PY - 2018 DO - https://doi.org/10.1039/c7cp08186c SN - 1463-9084 SN - 1463-9076 VL - 20 IS - 8 SP - 5626 EP - 5635 PB - Royal Society of Chemistry AN - OPUS4-44254 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Schönhals, Andreas T1 - Unraveling the dynamics of thin films of a miscible PVME/PS blend N2 - Dielectric spectroscopy (BDS) was employed to investigate the dynamics of thin films (7 – 200 nm) of a Poly (vinyl methyl ether) (PVME) / Polystyrene (PS) blend (50:50 wt%). For the BDS measurements Nano-Structured Capacitors (NSC) were employed, where films have a free surface. This method was applied for film thicknesses up to 36 nm. Thicker films were prepared between Crossed Electrodes Capacitors (CEC). The spectra of the films showed multiple processes. The first process was assigned to the -relaxation of a bulk-like layer. For films measured by NSC, its rates were higher compared to that of the bulk blend. This behavior was related to a PVME-rich free-surface layer. A second process was observed for films measured by CEC (process X) and the 36 nm film measured by NSC (process X2). This process was assigned to fluctuations of PVME constraint by PS. Its activation energy was found to be thickness dependent, due to the evidenced thickness dependency of the compositional heterogeneity. Finally, a third process with an activated temperature-dependence was observed for all films measured by NSC (process X1). It resembled the molecular fluctuations in an adsorbed layer found for films of pure PVME. T2 - Anual Meeting of the American Physical Society CY - Los Angeles, CA, USA DA - 05.03.2018 KW - Thin polymeric films PY - 2018 AN - OPUS4-44414 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Dong, S. A1 - Leng, J. A1 - Feng, Y. A1 - Liu, M. A1 - Stackhouse, C. J. A1 - Schönhals, Andreas A1 - Chiappisi, L. A1 - Gao, L. A1 - Chen, W. A1 - Shang, J. A1 - Jin, L. A1 - Qi, Z. A1 - Schalley, C. A. T1 - Structural water as an essential comonomer in supramolecular polymerization N2 - Although the concept of structural water that is bound inside hydrophobic pockets and helps to stabilize protein structures is well established, water has rarely found a similar role in supramolecular polymers. Water is often used as a solvent for supramolecular polymerization, however without taking the role of a comonomer for the supramolecular polymer structure. We report a low–molecular weight monomer whose supramolecular polymerization is triggered by the incorporation of water. The presence of water molecules as comonomers is essential to the polymerization process. The supramolecular polymeric material exhibits strong adhesion to surfaces, such as glass and paper. It can be used as a water-activated glue, which can be released at higher temperatures and reused many times without losing its performance. KW - Supra molecular polymerization PY - 2017 UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-432728 DO - https://doi.org/10.1126/sciadv.aao0900 SN - 2375-2548 VL - 3 IS - 11 SP - eaao0900, 1 EP - eaao0900, 8 PB - American Association for the Advancement of Science AN - OPUS4-43272 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Schönhals, Andreas T1 - Structure-property relationships of nanocomposite based on polylactide and layered double hydroxides as nanofiller N2 - Polymer-based nanocomposites attracted recently a lot of attention from both the applicative and fundamental point of research. While the former point of view is due to the properties improvement compared to the corresponding matrix polymers the latter aspect is related to interaction of polymers with solid surfaces and confinement effects. Here, nanocomposites based on poly(L-lactide) (PLA), which is a semi-crystalline polymer, and organically modified Layered Double Hydroxides (LDH) were prepared by melt blending, and investigated by a combination of Differential Scanning Calorimetry (DSC), Small- and Wide-Angle X-ray Scattering (SAXS, WAXS), and dielectric spectroscopy (BDS). Two different LDH materials were considered, which results in different morphologies of the nanocomposites. The influence of these different morphologies on the properties of the nanocomposites especially on the molecular mobility is discussed in detail. In general the structure of semi-crystalline polymers has to be described by a three phase model, consisting of a mobile amorphous (MAF), a crystalline (CF), and a rigid amorphous fraction (RAF). For nanocomposites based on semi-crystalline polymers the RAF is due to both the crystallites (RAFcrystal) and the filler (RAFfiller). The considered nanocomposites were further investigated by hyper and temperature modulated differential scanning calorimetry. For the first time the different phase fractions CF, MAF, RAFcrystal, and RAFfiller could be estimated independently from each other. T2 - Soft Matter Seminar Universität Halle CY - Halle, Germany DA - 21.11.2017 KW - Polymer based nanocomposites PY - 2017 AN - OPUS4-43098 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Schönhals, Andreas T1 - Broadband dielectric spectroscopy to study soft matter systems N2 - The basics of broadband dielectric spectroscopy were introduced in detail. The analysis of the data was discussed. As application of broadband dielectric spectroscopy the alpha-relaxation (dynamic glass transition) and the chain dynamics of polymers were ilustrated. Further the application of dielectric spectroscopy to polymerbased nanocomposites and high preformance polymers was discussed in detail. T2 - Kolloquiumsvotrag am Karlsruher Instiut of Technology CY - Karlsruhe, Germany DA - 05.12.2018 KW - Broadband dielectric spectroscopy PY - 2018 AN - OPUS4-46910 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CHAP A1 - Schönhals, Andreas A1 - Frick, B. A1 - Zorn, R. ED - Kremer, Friedrich ED - Loidl, Alois T1 - The scaling of the molecular dynamics of liquid crystals as revealed by broadband dielectric, specific heat, and neutron spectroscopy N2 - A combination of different complementary methods is employed to investigate scaling of the molecular dynamics of two different liquid crystals. Each method is sensitive to different kind of fluctuations and provides therefore a different window to look at the molecular dynamics. In detail, broadband dielectric spectroscopy is combined with specific heat spectroscopy and neutron scattering. As systems the nematic liquid crystal E7 and a discotic liquid crystalline pyrene are considered. First of all it was proven that both systems show all peculiarities which are characteristic for glassy dynamics and the glassy state. Especially for the nematic liquid crystal E7 it could be unambiguously shown by a combination of dielectric and specific heat spectroscopy that the tumbling mode is the underlying motional process responsible for glassy dynamics. Dielectric investigations on the discotic liquid crystalline pyrene reveal that at the phase transition from the plastic crystalline to the hexagonal columnar liquid crystalline phase the molecular dynamics changes from a more strong to fragile temperature dependence of the relaxation rates. Moreover a combination of results obtained by specific heat spectroscopy with structural methods allows an estimation of the length scale relevant for the glass transition. KW - Broadband dielectric spectroscopy KW - Specific heat spectroscopy KW - Rod-like liquid crystals KW - Discotic liquid crystals PY - 2018 UR - https://link.springer.com/content/pdf/10.1007%2F978-3-319-72706-6.pdf SN - 978-3-319-72705-9 SN - 978-3-319-72706-6 DO - https://doi.org/10.1007/978-3-319-72706-6_9 SN - 2190-930X SN - 2190-9318 SP - 279 EP - 306 PB - Springer International publishing AG CY - Cham, Switzerland ET - 1. AN - OPUS4-45624 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Schönhals, Andreas T1 - Thin polymer films as model systems for polymer nanocomposites N2 - Polymers at interfaces play a major role in a broad variety of applications ranging from engineering purposes (for instance polymer based nanocomposites) to high tech implications (for instance light emitting diodes). Here, thin films with thicknesses down to few nanometers are prepared on different substrates as model systems for polymer composites. The thin films are investigated by a combination of surface analytical and volume sensitive methods. As surface analytical methods atomic force microscopy (AFM), X-ray photoelectron spectroscopy (XPS), and contact angle measurements (CAM) are employed. As volume sensitive broadband dielectric spectroscopy (BDS), specific heat spectroscopy (SHS), and ellipsometry are used. Especially attention is paid to understand the glass transition behavior of thin films because the glass transition is the key phenomenon determines the application of polymers also in thin films. To understand the glass transition behavior of thin films, which is controversially discussed in literature, a three layer model is discussed. Firstly, a mobile surface layer is assumed at polymer air interface of the film due to missing of segment/segment interactions. Secondly, in the middle of the film a bulk-like layer should be expected. Thirdly, for polymers having non-repulsive interactions with the substrate an irreversibly adsorbed layer is expected to be formed. Due the adsorption the molecular mobility of the segments in this layer is slowed down. What is measured for the glass transition of thin films is a complicated average of all of these effects. The different layers are hardly to address separately. Therefore, in the presentation especially model systems are selected and investigated to verify the layer model. T2 - Kolloquiumsvortrag and der Universität des Saarlandes CY - Saarbrücken, Gemany DA - 20.11.2018 KW - Thin polymer films PY - 2018 AN - OPUS4-46692 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - GEN A1 - Schönhals, Andreas A1 - Zorn, R. T1 - Quasi-elastic scattering of high free volume polymers by neutron time-of-flight spectroscopy N2 - Experimental report to proposal 13562 Quasi-elastic scattering of the polymer with intrinsic microporoasity PIM-1 is measured by neutron time-of-flight spectroscopy and discussed. KW - Neutron scattering KW - PIM-1 PY - 2018 SP - 1 EP - 2 CY - Garching AN - OPUS4-46693 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Schönhals, Andreas T1 - Nano-sized Relaxation Spectroscopy of Miscible PVME/PS Blend Thin Films N2 - The moleculat dynamics of ultra thin films of polystyrene/poly(vinyl methyl ether) blends as revealed by nanosized specific heat and dielectric spectroscopy is discussed. T2 - Viscous liquids and the glass transition XV CY - Søminestationen, Holbæk, Denmark DA - 21.06.2018 KW - Thin polymeric films KW - Dielectric spectroscopy KW - Specific heat spectroscopx PY - 2018 AN - OPUS4-45280 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Schönhals, Andreas T1 - Glass transition of thin polymeric films as revealed by calorimetric and dielectric techniques N2 - The structure and dynamics of thin polymeric films is reviewed and discussed in the frame work of novel theoretical approaches T2 - Lähnwitzseminar on Calorimetry CY - Rostock-Warnemünde, Germany DA - 03.06.2018 KW - Thin polymeric films KW - Dielectric spectroscopy KW - Thermal süectroscopy PY - 2018 AN - OPUS4-45164 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Schönhals, Andreas T1 - Growth kinetics and molecular mobility of irreversibly adsorbed layers in thin polymer films N2 - In well-annealed thin polymer films, with non-repulsive polymer/substrate interactions, an irreversibly adsorbed layer is expected to from. These adsorbed layers have shown greate potential for technological applications. However, their growth kinetics and molecular dynamics are still not fully understood. This is partly due to the hard accessibility of these layers in thin films. Here, the irreversibly adsorbed layers of homopolymer thin films are revealed by solvent-leaching experiments. First, the growth kinetics of these layers is investigated as a function of annealing time, annealing temperature, leaching time and the original filme thickness. The film thickness, topography and the quality of the adsorbed layer is controlled by Atomic Force Microscopy (AFM). Secondly, the molecular mobility of the adsorbed layer is investigated by Broadband Dielectric Spectroscopy (BDS). A recently developed nanostructured capacitor arrangement is employed to measure the layer with a free surface. The results are quantitatively compared and discussed with respect to recently published work. T2 - 10th Conference on Broadband Dielectric Spectroscopy and its Applications CY - Brussles, Belgium DA - 26.08.2018 KW - Thin polymer films PY - 2018 AN - OPUS4-45837 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - GEN A1 - Schönhals, Andreas A1 - Zorn, R. T1 - Elastic scans on highly permeable glassy polynorbornenes N2 - Experimantal Report to proposal 13603: Elastic Scans on Highly Permeable Glassy Polynorbornenes are measured by neutron backscatering and discuused KW - Neutron backscattering KW - Glassy polynorbornenes PY - 2018 SP - 1 EP - 2 CY - Garching (MLZ) AN - OPUS4-45436 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Yin, Huajie A1 - Napolitano, S. A1 - Schönhals, Andreas T1 - Molecular mobility and glass transition of thin films of poly(bisphenol A carbonate) N2 - Glass transition behavior of thin poly(bisphenol A carbonate) (PBAC) films capped between two aluminum (Al) layers is investigated by means of dielectric expansion dilatometry and dielectric relaxation spectroscopy accompanied by contact angle measurements. The thermal glass transition temperature is more or less independent of the film thickness down to 20 nm. For thickness below 20 nm, an increase of Tg is observed. Meanwhile, an increase of the relaxation time at a fixed temperature is observed for the film with the thickness of 19 nm on the basis of a careful analysis of the temperature dependence of the relaxation rates. A more detailed analysis of the relaxation map reveals that the Vogel temperature increases and the fragility decreases systematically with decreasing film thickness. These properties are discussed in terms of the formation of a boundary layer with PBAC segments adsorbed onto the Al electrode due to the strong interaction between the Al and PBAC layers (2.51 mJ/m²), which results in a reduced molecular mobility with regard to bulk PBAC behavior. As the dielectric strength is proportional to the number of segments fluctuating on the time and length scale of the dynamic glass transition, it is used as a unique probe of the deviations from bulk behavior. The temperature dependence of the penetration depth of the interfacial interactions on the structural relaxation is further quantitatively determined. The dynamic length scale of the perturbations into the chain conformations responsible for the deviation from bulk behavior is estimated to be smaller than 9 nm. PY - 2012 DO - https://doi.org/10.1021/ma202127p SN - 0024-9297 SN - 1520-5835 VL - 45 IS - 3 SP - 1652 EP - 1662 PB - American Chemical Society CY - Washington, DC AN - OPUS4-25472 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Yin, Huajie A1 - Schönhals, Andreas T1 - Calorimetric glass transition of ultrathin poly(bisphenol A carbonate) films N2 - Specific heat spectroscopy in the frequency range from 1 Hz to 10³ Hz with a sensitivity of pJ K-1 was employed to study the glass transition behavior of ultrathin poly(bisphenol A carbonate) (PBAC) films with thicknesses ranging from 192 nm down to 10 nm. The amplitude and the phase angle of the complex differential voltage as a measure of the complex heat capacity were obtained as a function of temperature at a given frequency simultaneously. Both spectra are used to determine the dynamic glass transition temperature as a function of both the frequency and the film thickness. As the main result no thickness dependence of the dynamic glass transition temperature was observed down to a film thickness of 10 nm within the experimental uncertainty of ±3 K. The obtained data were compared with literature results in detail. PY - 2012 DO - https://doi.org/10.1039/c2sm26174j SN - 1744-683X VL - 8 IS - 35 SP - 9132 EP - 9139 PB - RSC Publ. CY - Cambridge AN - OPUS4-26379 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Boucher, V.M. A1 - Cangialosi, D. A1 - Yin, Huajie A1 - Schönhals, Andreas A1 - Alegría, A. A1 - Colmenero, J. T1 - Tg depression and invariant segmental dynamics in polystyrene thin films N2 - We investigate the segmental dynamics and glass transition temperature (Tg) of polystyrene (PS) thin films. The former is investigated by alternating current (AC) calorimetry and dielectric spectroscopy (BDS). The Tg, underlying the equilibrium to out-of-equilibrium crossover from the supercooled liquid to the glass, is obtained by differential scanning calorimetry (DSC) and capacitive dilatometry (CD). We show that the intrinsic molecular dynamics of PS are independent of the film thickness both for the freestanding and supported films, whereas Tg decreases with film thickness from several microns down to 15 nm. This result is found for complementary methods and in a simultaneous measurement in BDS and CD. This questions the widespread notion that segmental mobility and the equilibrium to out-of-equilibrium transition are, under any experimental conditions, fully interrelated. For thin films, it appears that the molecular mobility and Tg are affected differently by geometrical factors. PY - 2012 DO - https://doi.org/10.1039/c2sm25419k SN - 1744-683X VL - 8 IS - 19 SP - 5119 EP - 5122 PB - RSC Publ. CY - Cambridge AN - OPUS4-25805 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Yin, Huajie A1 - Schönhals, Andreas T1 - Glass transition and segmental dynamics of ultrathin poly(bisphenol A carbonate) films N2 - Broadband dielectric spectroscopy (BDS), capacitive scanning dilatometry (CSD) and differential ac-chip calorimetry (DACC) were used to examine the glass transition and segmental dynamics of ultrathin poly(bisphenol A carbonate) (PBAC) films. An increase of Vogel temperature (T0) as well as glass transition temperature (Tg) with decreasing film thickness was observed when the thickness is less than 20 nm. Moreover, the segmental relaxation time at a fixed temperature was found to increase for the aluminium (Al) capped PBAC films (<20 nm) in the BDS measurements, whereas in the DACC measurements no thickness dependency of the segmental dynamics was detected within the experimental error limit for the supported PBAC films (10-55 nm). These properties are discussed in terms of the thin film geometry and the relevant interfacial interaction between the polymer and the substrate. T2 - 6th International conference on times of polymers (TOP) and composites CY - Ischia, Italy DA - 10.06.2012 KW - Ultrathin film KW - Poly(bisphenol A carbonate) KW - Glass transition KW - Aluminium KW - Dielectric thin films KW - Differential scanning calorimetry KW - Permittivity KW - Polymer films PY - 2012 SN - 978-0-7354-1061-9 DO - https://doi.org/10.1063/1.4738399 N1 - Serientitel: AIP conference proceedings – Series title: AIP conference proceedings IS - 1459 SP - 64 EP - 67 AN - OPUS4-26349 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Omar, Hassan A1 - Ahmadi, Shayan A1 - Szymoniak, Paulina A1 - Schönhals, Andreas T1 - Molecular Mobility of Thin Films of Poly (bisphenol-A carbonate) Capped and with one Free Surface: From Bulk-like Samples down to the Adsorbed Layer N2 - The molecular mobility of thin films of poly(bisphenol A carbonate) (PBAC) was systematically investigated using broadband dielectric spectroscopy, employing two distinct electrode configurations. First, films were prepared in a capped geometry between aluminum electrodes employing a crossed electrode capacitor (CEC) configuration, down to film thicknesses of 40 nm. The Vogel temperature, derived from the temperature dependence of relaxation rate of the α-relaxation, increases with decreasing film thickness characterized by an onset thickness. The onset thickness depends on the annealing conditions, with less intense annealing yielding a lower onset thickness. Additionally, a broadening of the β-relaxation peak was observed with decreasing thickness, attributed to the interaction of phenyl groups with thermally evaporated aluminum, resulting in a shift of certain relaxation modes to higher temperatures relative to the bulk material. A novel phenomenon, termed the slow Arrhenius process (SAP), was also identified in proximity to the α-relaxation temperature. For films with thicknesses below 40 nm, nanostructured electrodes (NSE) were utilized, incorporating nanostructured silica spacers to establish a free surface with air. This free surface causes an enhancement in the molecular mobility for the 40 nm sample, preserving the β-relaxation as a distinct peak. The α-relaxation was detectable in the dielectric loss down to 18 nm, shifting to higher temperatures as film thickness is decreased. Notably, the onset thickness for the increase in Vogel temperature was lower in the NSE configuration compared to the CEC setup, attributed to the presence of the polymer-air interface. KW - Thin polymer films PY - 2025 UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-623422 DO - https://doi.org/10.1039/d4sm01238k SN - 1744-6848 VL - 21 IS - 2 SP - 241 EP - 254 PB - RSC AN - OPUS4-62342 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Kimiaei, E. A1 - Farooq, M. A1 - Szymoniak, Paulina A1 - Ahmadi, Shayan A1 - Babaeipour, S. A1 - Schönhals, Andreas A1 - Österberg, M. T1 - The role of lignin as interfacial compatibilizer in designing lignocellulosic-polyester composite films N2 - Advancing nanocomposites requires a deep understanding and careful design of nanoscale interfaces, as interfacial interactions and adhesion significantly influence the physical and mechanical properties of these materials. This study demonstrates the effectiveness of lignin nanoparticles (LNPs) as interfacial compatibilizer between hydrophilic cellulose nanofibrils (CNF) and a hydrophobic polyester, polycaprolactone (PCL). In this context, we conducted a detailed analysis of surface-to-bulk interactions in both wet and dry conditions using advanced techniques such as quartz crystal microbalance with dissipation (QCM-D), atomic force microscopy (AFM), water contact angle (WCA) measurements, broadband dielectric spectroscopy (BDS), and inverse gas chromatography (IGC). QCM-D was employed to quantify the adsorption behavior of LNPs on CNF and PCL surfaces, demonstrating LNPs’ capability to interact with both hydrophilic and hydrophobic phases, thereby enhancing composite material properties. LNPs showed extensive adsorption on a CNF model film (1186 ± 178 ng.cm−2) and a lower but still significant adsorption on a PCL model film (270 ± 64 ng.cm−2). In contrast, CNF adsorption on a PCL model film was the lowest, with a sensed mass of only 136 ± 35 ng.cm−2. These findings were further supported by comparing the morphology and wettability of the films before and after adsorption, using AFM and WCA analyses. Then, to gain insights into the molecular-level interactions and molecular mobility within the composite in dry state, BDS was employed. The BDS results showed that LNPs improved the dispersion of PCL within the CNF network. To further investigate the impact of LNPs on the composites’ interfacial properties, IGC was employed. This analysis showed that the composite films containing LNPs exhibited lower surface energy compared to those composed of only CNF and PCL. The presence of LNPs likely reduced the availability of surface hydroxyl groups, thus modifying the physicochemical properties of the interface. These changes were particularly evident in the heterogeneity of the surface energy profile, indicating that LNPs significantly altered the interfacial characteristics of the composite materials. Overall, these findings emphasize the necessity to control the interfaces between components for next-generation nanocomposite materials across diverse applications. KW - Lignin KW - Nanocomposites PY - 2024 UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-615098 DO - https://doi.org/10.1016/j.jcis.2024.10.083 SN - 0021-9797 VL - 679 SP - 263 EP - 275 PB - Elsevier Inc. AN - OPUS4-61509 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Xu, Q. A1 - Szymoniak, Paulina A1 - Kolmangadi, Mohamed A. A1 - Yang, Z. A1 - Wang, S. A1 - Gao, Y. A1 - Shang, J. A1 - Hunger, J. A1 - Aldiyarov, A. A1 - Schönhals, Andreas A1 - Ge, Y. A1 - Qi, Z. T1 - Molecular engineering of supramolecular polymer adhesive with confined water and a single crown ether N2 - Here, we report a water-induced supramolecular polymer built from confined structural water and an intrinsic amphiphilic macrocyclic self-assembly in a nanophase separated structure. The newly designed crown ether macrocycle, featuring strong hydrophilic hydrogen bonding receptor selenoxide and a synergistical hydrophobic selenium-substituted crown core, confines the structural water in a segregated, interdigitated architecture. Although water molecules typically freeze around 0 °C, the confined structural water in this supramolecular polymer remains in a liquid-like state down to 80 °C. Previous studies suggest that multiple crown ether units are needed to generate structural water. However, here, one unit is sufficient to control the formation and disappearance of structural water and consequent supramolecular polymerization. Typically, the DC conductivity of water shows Arrhenius temperature dependency (lnσDC ∝ 1/T). In contrast, this new crown unit maintains water in confined states, which exhibit a Vogel/Fulcher/Tammann behavior (lnσDC ∝ 1/(T-T0)) at temperatures above the glass transition temperature. Moreover, this water-induced supramolecular polymer exhibits remarkable adhesion properties to hydrophilic surfaces and maintains tough adhesion at low temperatures. These findings show how a single small macrocycle can govern the complex structure and functionality of water in supramolecular systems. KW - Supramolecular polymerization PY - 2025 UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-623631 DO - https://doi.org/10.1039/D4SC06771A SN - 2041-6539 VL - 16 SP - 1 EP - 9 PB - RSC AN - OPUS4-62363 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Li, Z. A1 - Raab, A. A1 - Kolmangadi, Mohamed Aejaz A1 - Busch, M. A1 - Grunwald, M. A1 - Demel, F. A1 - Bertram, F. A1 - Kityk, A. V. A1 - Schönhals, Andreas A1 - Laschat, S. A1 - Huber, P. T1 - Self-Assembly of Ionic Superdiscs in Nanopores N2 - Discotic ionic liquid crystals (DILCs) consist of self-assembled superdiscs of cations and anions that spontaneously stack in linear columns with high one-dimensional ionic and electronic charge mobility, making them prominent model systems for functional soft matter. Compared to classical nonionic discotic liquid crystals, many liquid crystalline structures with a combination of electronic and ionic conductivity have been reported, which are of interest for separation membranes, artificial ion/proton conducting membranes, and optoelectronics. Unfortunately, a homogeneous alignment of the DILCs on the macroscale is often not achievable, which significantly limits the applicability of DILCs. Infiltration into nanoporous solid scaffolds can, in principle, overcome this drawback. However, due to the experimental challenges to scrutinize liquid crystalline order in extreme spatial confinement, little is known about the structures of DILCs in nanopores. Here, we present temperaturedependent high-resolution optical birefringence measurement and 3D reciprocal space mapping based on synchrotron X-ray scattering to investigate the thermotropic phase behavior of dopamine-based ionic liquid crystals confined in cylindrical channels of 180 nm diameter in macroscopic anodic aluminum oxide membranes. As a function of the membranes’ hydrophilicity and thus the molecular anchoring to the pore walls (edge-on or face-on) and the variation of the hydrophilic−hydrophobic balance between the aromatic cores and the alkyl side chain motifs of the superdiscs by tailored chemical synthesis, we find a particularly rich phase behavior, which is not present in the bulk state. It is governed by a complex interplay of liquid crystalline elastic energies (bending and splay deformations), polar interactions, and pure geometric confinement and includes textural transitions between radial and axial alignment of the columns with respect to the long nanochannel axis. Furthermore, confinement-induced continuous order formation is observed in contrast to discontinuous first-order phase transitions, which can be quantitatively described by Landau-de Gennes free energy models for liquid crystalline order transitions in confinement. Our observations suggest that the infiltration of DILCs into nanoporous solids allows tailoring their nanoscale texture and ion channel formation and thus their electrical and optical functionalities over an even wider range than in the bulk state in a homogeneous manner on the centimeter scale as controlled by the monolithic nanoporous scaffolds. KW - Ionic Liquid Crystals KW - Nanopropous materials KW - Landau de-Gennes analysis KW - X-ray scattering KW - Optical birefringence PY - 2024 UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-600797 DO - https://doi.org/10.1021/acsnano.4c01062 SN - 1936-0851 VL - 18 IS - 22 SP - 14414 EP - 14426 PB - ACS AN - OPUS4-60079 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Krause, Christina A1 - Zorn, R. A1 - Frick, B. A1 - Schönhals, Andreas T1 - Quasi- and inelastic neutron scattering to investigate the molecular dynamics of discotic molecules in the bulk N2 - In- and quasielastic neutron scattering is employed to investigate both the vibrational density of states and the molecular dynamics of two homologous discotic liquid crystals (DLC) with different length of the alkyl side chain based on a triphenylene derivate. For both compounds characteristic low frequency excess contributions to the vibrational density of states are found. Therefore it is concluded that these liquid crystals show a glass-like behaviour. Elastic scans further show that in these materials a rich molecular dynamics takes place. T2 - QENS/WINS 2014 - 11th International Conference on Quasielastic Neutron Scattering and 6th International Workshop on Inelastic Neutron Spectrometers CY - Autrans, France DA - 2014-05-11 PY - 2015 UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-325477 DO - https://doi.org/10.1051/epjconf/20158302017 SN - 2100-014X VL - 83 SP - 02017-1 EP - 02017-4 PB - EDP Sciences CY - Les Ulis AN - OPUS4-32547 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CHAP A1 - Yin, Huajie A1 - Schönhals, Andreas ED - Utracki, L.A. ED - Wilkie, C. A. T1 - Broadband dielectric spectroscopy on polymer blends N2 - In this chapter broadband dielectric spectroscopy (BDS) is employed to polymeric blend systems. In its modern form BDS can cover an extraordinary broad frequency range from 10-4 to 1012 Hz. Therefore, molecular and collective dipolar fluctuations, charge transport, and polarization effects at inner phase boundaries can be investigated in detail including its temperature dependence. In the first part of the chapter, the theoretical basics of dielectric spectroscopy are briefly introduced covering both static and dynamic aspects. This section is followed by short description of the various experimental techniques to cover this broad frequency range. To provide the knowledge to understand the dielectric behavior of polymeric blend systems, the dielectric features of amorphous homopolymers are discussed in some detail. This concerns an introduction of the most important relaxation processes observed for these polymers (localized fluctuations, segmental dynamics related to the dynamic glass transition, chain relaxation), a brief introduction to the conductivity of disordered systems as well as polarization effects at phase boundaries. Theoretical models for each process are shortly discussed. In the last paragraph the dielectric behavior of polymer blends is reviewed where special attention is paid to binary systems for the sake of simplicity. In detail the dielectric behavior of binary miscible blends is described. The two most important experimental facts like the broadening of the dielectric relaxation spectra and the dynamic heterogeneity of the segmental dynamics are addressed in depth. Appropriate theoretical approaches like the temperature-driven concentration fluctuation model and the self-concentration idea are introduced. PY - 2014 SN - 978-94-007-6063-9 SN - 978-94-007-6064-6 SN - 978-94-007-6065-3 DO - https://doi.org/10.1007/978-94-007-6064-6_14 SP - Chapter 12, 1299 EP - 1356 PB - Springer Science + Business Media AN - OPUS4-32087 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Schönhals, Andreas T1 - Molecular Dynamics of linear poly(n-isopropylacrylamide) in water below and above the phase transition: A broadband dielectric relaxation spectroscopy study T2 - Polydays 2014 CY - Berlin, Germany DA - 2014-09-30 PY - 2014 AN - OPUS4-32279 LA - deu AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Fahmy, A. A1 - Mohamed, T.A. A1 - Schönhals, Andreas T1 - Structure of plasma poly(acrylic acid): Influence of pressure and dielectric properties N2 - Thin poly(acrylic acid) PAA films were deposited by pulsed plasma polymerization on different organic and inorganic substrates. The structure–property relationships of the deposited acrylic acid polymers were studied in dependence on the monomer pressure by various techniques and probes. The surface and bulk properties of the plasma deposited films were investigated by X-ray photoelectron spectroscopy, attenuated total reflection infrared, and broad band dielectric spectroscopy. The experimental infrared frequencies of PAA films are compared with those predicted from quantum mechanical calculation. The concentration of the COOH groups in the film (stored in ambient air) decreased by about 15 % compared to the as-prepared sample. The plasma deposited PAA probably form a highly branched product. However, the dielectric measurements show that in addition to the hydrogen bonds, self condensation process was able to hinder the localized fluctuation as well. These processes lead to form a cross-linked network polymer film. Nevertheless, a low energy is sufficient to break these processes during heating at atmospheric pressure. Therefore, homogenized samples with free branches (functional group) were obtained after a first heating with structures close to conventional polymerized acrylic acid. Thus, a thermally stable product was obtained. KW - Acrylic acid KW - Plasma polymerization KW - Dielectric properties KW - Thermal stability KW - Aging KW - Monomer pressure PY - 2015 DO - https://doi.org/10.1007/s11090-014-9603-8 SN - 0272-4324 VL - 35 IS - 2 SP - 303 EP - 320 PB - Plenum Publ. Corp. CY - New York, NY, USA AN - OPUS4-32711 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Dhotel, A. A1 - Chen, Z. A1 - Sun, J. A1 - Youssef, B. A1 - Saiter, J.-M. A1 - Schönhals, Andreas A1 - Tan, L. A1 - Delbreilh, L. T1 - From monomers to self-assembled monolayers: the evolution of molecular mobility with structural confinements N2 - The effect of structural constriction on molecular mobility is investigated by broadband dielectric spectroscopy (BDS) within three types of molecular arrangements: monomers, oligomers and self-assembled monolayers (SAMs). While disordered monomers exhibit a variety of cooperative and local relaxation processes, the constrained nanodomains of oligomers and highly ordered structure of monolayers exhibit much hindered local molecular fluctuations. Particularly, in SAMs, motions of the silane headgroups are totally prevented whereas the polar endgroups forming the monolayer canopy show only one cooperative relaxation process. This latter molecular fluctuation is, for the first time, observed independently from other overlapping dielectric signals. Numerous electrostatic interactions among those dipolar endgroups are responsible for the strong cooperativity and heterogeneity of the canopy relaxation process. Our data analyses also revealed that the bulkiness of dipolar endgroups can disrupt the organization of the monolayer canopy thus increasing their ability to fluctuate as temperature is increased. PY - 2015 DO - https://doi.org/10.1039/c4sm01893a SN - 1744-683X VL - 11 IS - 4 SP - 719 EP - 731 PB - RSC Publ. CY - Cambridge AN - OPUS4-32378 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Schönhals, Andreas T1 - Behavior of Ultra-Thin Polymerich Films as Investigated by a Combination of Complementary Methods T2 - Kolloquiumsvortrag Universität Bielefeld, Fakultät für Physik CY - Bielefeld, Germany DA - 2014-12-12 PY - 2014 AN - OPUS4-32354 LA - deu AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Brás, A.R. A1 - Fonseca, I.M. A1 - Dionísio, M. A1 - Schönhals, Andreas A1 - Affouard, F. A1 - Correia, N.T. T1 - Influence of nanoscale confinement on the molecular mobility of ibuprofen N2 - The molecular mobility of ibuprofen confined to a mesoporous silica host (MCM-41) of 3.6 nm pore diameter is investigated by dielectric relaxation spectroscopy. It is confirmed that crystallization is suppressed; therefore, depending on the temperature, the guest exists in the glassy and supercooled state inside of the pores. A detailed relaxation map is provided where multiple processes are dynamically characterized, comprised of three processes that are also found for the bulk and two additional ones. The bulk-like processes include two secondary processes, a simple thermally activated one, a γ process and a Johari–Goldstein βJG process, and the one associated with the dynamic glass transition of molecules located in the pore center (α process). In confinement, all of these processes display deviations in its dynamical behavior relative to the bulk, the most dramatic one undergone by the α process, which exhibits Arrhenius-like temperature dependence upon approaching the glass transition instead of Vogel/Fulcher/Tammann/Hesse (VFTH) scaling as obeyed by the bulk. The two additional relaxations are associated with the dynamical behavior of hydrogen-bonded ibuprofen molecules lying in an interfacial layer near the pore wall, an S process for which the mobility is strongly reduced relative to the α process and a Debye-like D process for which the dynamics is closely correlated to the dynamics of the interfacial process, both exhibiting VFTH temperature dependencies. The comparison with the behavior of the same guest in the analogous host, SBA-15, with a higher pore diameter (8.6 nm) leads to the conclusion that the bulk-like mobility associated with the dynamic glass transition undergoes finite size effects being accelerated upon a decrease of the pore size with a concomitant reduction of the glass transition temperature relative to the bulk, 22 and 32 K, respectively, for the 8.6 and 3.6 nm pore diameters. The continuous decrease in the separation between the α- and βJG-trace with pore size decrease allows one to conclude that confined ibuprofen is a suitable guest molecule to test the Coupling Model that predicts a transformation of the α process into a βJG-mode under conditions of an extreme nanoconfinement. The overall behavior inside of pores is consistent with the existence of two distinct dynamical domains, originated by ibuprofen molecules in the core of the pore cavity and adjacent to the pore wall, from which a clear picture is given by molecular dynamics simulation. PY - 2014 DO - https://doi.org/10.1021/jp500630m SN - 1932-7447 SN - 1089-5639 VL - 118 IS - 25 SP - 13857 EP - 13868 PB - Soc. CY - Washington, DC AN - OPUS4-31170 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Schönhals, Andreas T1 - Molecular Dynamics of Discotic Liquid Crystals in the Bulk and embedded in Nanochannels T2 - 8th International Conference on Broadband Dielectric Spectroscopy and its Applications CY - Wisla, Poland DA - 2014-09-15 PY - 2014 AN - OPUS4-31464 LA - deu AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Schönhals, Andreas T1 - Molecular Dynamics of Linear Poly(N-isopropylacrylamide) in Water below and above the Phase Transition: A Broadband Dielectric Relaxation Spectroscopy Study T2 - 8th International Conference on Broadband Dielectric Spectroscopy and its Applications CY - Wisla, Poland DA - 2014-09-15 PY - 2014 AN - OPUS4-31465 LA - deu AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Kityk, A.V. A1 - Busch, M. A1 - Rau, D. A1 - Calus, S. A1 - Cerclier, C.V. A1 - Lefort, R. A1 - Morineau, D. A1 - Grelet, E. A1 - Krause, Christina A1 - Schönhals, Andreas A1 - Frick, B. A1 - Huber, P. T1 - Thermotropic orientational order of discotic liquid crystals in nanochannels: an optical polarimetry study and a Landau-de Gennes analysis N2 - Optical polarimetry measurements of the orientational order of a discotic liquid crystal based on a pyrene derivative confined in parallelly aligned nanochannels of monolithic, mesoporous alumina, silica, and silicon as a function of temperature, channel radius (3–22 nm) and surface chemistry reveal a competition of radial and axial columnar orders. The evolution of the orientational order parameter of the confined systems is continuous, in contrast to the discontinuous transition in the bulk. For channel radii larger than 10 nm we suggest several, alternative defect structures, which are compatible both with the optical experiments on the collective molecular orientation presented here and with a translational, radial columnar order reported in previous diffraction studies. For smaller channel radii our observations can semi-quantitatively be described by a Landau–de Gennes model with a nematic shell of radially ordered columns (affected by elastic splay deformations) that coexists with an orientationally disordered, isotropic core. For these structures, the cylindrical phase boundaries are predicted to move from the channel walls to the channel centres upon cooling, and vice-versa upon heating, in accord with the pronounced cooling/heating hystereses observed and the scaling behavior of the transition temperatures with the channel diameter. The absence of experimental hints of a paranematic state is consistent with a biquadratic coupling of the splay deformations to the order parameter. PY - 2014 DO - https://doi.org/10.1039/c4sm00211c SN - 1744-683X VL - 10 IS - 25 SP - 4522 EP - 4534 PB - RSC Publ. CY - Cambridge AN - OPUS4-30866 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Schönhals, Andreas A1 - Papadakis, C.M. T1 - Editorial - Special issue in honor of Friedrich Kremer N2 - Prof. Dr. Friedrich Kremer is celebrating his 65th birthday this year. Furthermore, also for this reason, he resigned from the position as an Editor-in-Chief of the journal Colloid and Polymer Science. In his more than 20 years of successful editorship, he has substantially contributed to develop Colloid and Polymer Science to become a leading international journal in the field of polymers and colloids including their manifold connections with other branches of science. He will remain in a close connection to the journal as the new Chief Advisory Editor. To appreciate both his 65th birthday and his prosperous engagement for this journal, Springer is pleased to launch the present special issue of Colloid and Polymer Science dedicated to Prof. Dr. Friedrich Kremer. Friends, editors, and colleagues, as well as coworkers and former students contribute to this special issue with their own selected original scientific work in order to honor Prof. Dr. Friedrich Kremer not only as a leading scientist but also as a person with an outstanding personality. PY - 2014 DO - https://doi.org/10.1007/s00396-014-3292-y SN - 0303-402X SN - 1435-1536 VL - 292 IS - 8 SP - 1735 EP - 1736 PB - Springer CY - Berlin AN - OPUS4-31185 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Krause, Christina A1 - Zorn, R. A1 - Frick, B. A1 - Schönhals, Andreas T1 - Thermal properties and vibrational density of states of a nanoconfined discotic liquid crystal N2 - Neutron scattering is employed to investigate the vibrational density of states (VDOS) of the discotic liquid crystal 2,3,6,7,10,11-hexakis[hexyloxy] triphenylene (HAT6) confined to the pores of alumina oxide membranes with different pore sizes. Additionally, the phase transitions were studied by differential scanning calorimetry. The transitions were observed down to the smallest pore size. The decrease of the transition enthalpies versus inverse pore size for both transitions implies an increase of the amount of disordered amorphous material. By extrapolation of its pore size dependence, a critical pore diameter for structure formation of 17 nm is estimated. Similar to the bulk, excess contributions to the VDOS (Boson peak) are also observed for confined HAT6. The Boson peak gains in intensity and shifts to lower frequencies with decreasing pore diameter. This is discussed in the framework of a softening of HAT6 induced by the confinement due to a less-developed plastic crystalline state inside the pores compared to the bulk. KW - Discotic liquid crystals KW - Confinement KW - Neutron scattering KW - Boson peak PY - 2014 DO - https://doi.org/10.1007/s00396-014-3247-3 SN - 0303-402X SN - 1435-1536 VL - 292 IS - 8 SP - 1949 EP - 1960 PB - Springer CY - Berlin AN - OPUS4-31254 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Schönhals, Andreas T1 - Molecules in Nanometer Confinement investigated by Dieletric, Thermal and Neutron Spectroscopy T2 - Kolloquiumsvortrag Universität Rouen CY - Rouen, France DA - 2013-12-10 PY - 2013 AN - OPUS4-30020 LA - deu AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Schönhals, Andreas T1 - Crystallization behavior of nanocomposites based on poly(L-lactide) and layered doubled hydroxides – Unbiased determination of the rigid amorphous phase due to the crystals and the nanofiller N2 - Semicrystalline polymers have to be described by a three phase model consisting of a mobile amorphous (MAF), a crystalline (CF), and a rigid amorphous fraction (RAF). For nanocomposites based on a semicrystalline polymer the RAF is due to both the crystallites (RAFcrystal) and the filler (RAFfiller). In most cases a separation of both contributions is not possible without further assumptions. Polymer nanocomposite based on poly(L-lactide) and MgAl layered double hydroxide nanofiller were prepared. Due to the low crystallization rate of PLA its crystallization can be suppressed by a high enough cooling rate, and the RAF is due only to the nanofiller. The MAF, CF, and RAF were estimated by Temperature Modulated DSC. For the first time CF, MAF, RAFcrystal, and RAFfiller could be estimated. It was found, that RAFfiller increases linearly with the concentration of the nanofiller. Furthermore, RAFcrystal is only slightly influenced by the presence of the nanofiller. T2 - Marchmetting American Physical Society CY - New Orleans, USA DA - 13.03.2017 KW - Nanocomposites PY - 2017 AN - OPUS4-39554 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Asadujjaman, Asad A1 - Bertin, Annabelle A1 - Schönhals, Andreas T1 - Dielectric analysis of the upper critical solution temperature behaviour of a poly(acrylamide-coacrylonitrile) copolymer system in water N2 - A copolymer consisting of acrylamide (AAm) and acrylonitrile (AN) in aqueous solution was investigated using broadband dielectric spectroscopy at frequencies between 10⁻¹ Hz and 10⁶ Hz in the temperature range from 2 °C to 60 °C. This system shows an UCST phase behavior. The phase transition and aggregation behavior is monitored by both the temperature and frequency dependence of the complex conductivity σ*(f, T), where the AN fraction and the concentration of the solution were varied. Additionally, the dielectric data are compared with the results obtained from dynamic light scattering measurements. The temperature dependence of the DC conductivity (σDC) of the copolymer solution is monitored and the phase transition temperature (PTT) of the poly(AAm-co-AN) copolymer is deduced from a change in the T-dependence of the DC conductivity. The change in σDC can be explained by decreased effective charge carrier mobility and a reduction of the effective charge number density at temperatures below the phase Transition temperature of the poly(AAm-co-AN) solution. A pronounced interfacial polarization effect on the frequency dependence of the real part of the conductivity (σ') is observed at temperatures below the phase Transition temperature. The charge carriers are blocked at the formed aggregates giving rise to this interfacial polarization. The dependence of the interfacial polarization on the acrylonitrile fraction in the copolymer and the concentration of the solution is studied in detail and conclusions concerning the internal structures of the copolymer aggregates are drawn. KW - Thermoresponsive polymres PY - 2017 DO - https://doi.org/10.1039/c6sm02684b SN - 1744-6848 SN - 1744-683X VL - 13 IS - 12 SP - 2384 EP - 2393 PB - Royl Society of Chemistry Publishing AN - OPUS4-39556 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Madkour, Sherif A1 - Szymoniak, Paulina A1 - Schick, Ch. A1 - Schönhals, Andreas T1 - Unexpected behavior of ultra-thin films of blends of polystyrene/poly(vinyl methyl ether) studied by specific heat spectroscopy N2 - Specific heat spectroscopy (SHS) employing AC nanochip calorimetry was used to investigate the glassy dynamics of ultra-thin films (thicknesses: 10 nm–340 nm) of a polymer blend, which is miscible in the bulk. In detail, a Poly(vinyl methyl ether) (PVME)/Polystyrene (PS) blend with the composition of 25/75 wt. % was studied. The film thickness was controlled by ellipsometry while the film topography was checked by atomic force microscopy. The results are discussed in the framework of the balance between an adsorbed and a free surface layer on the glassy dynamics. By a self-assembling process, a layer with a reduced mobility is irreversibly adsorbed at the polymer/substrate interface. This layer is discussed employing two different scenarios. In the first approach, it is assumed that a PS-rich layer is adsorbed at the substrate. Whereas in the second approach, a PVME-rich layer is suggested to be formed at the SiO2 substrate. Further, due to the lower surface tension of PVME, with respect to air, a nanometer thick PVME-rich surface layer, with higher molecular mobility, is formed at the polymer/air interface. By measuring the glassy dynamics of the thin films of PVME/PS in dependence on the film thickness, it was shown that down to 30 nm thicknesses, the dynamic Tg of the whole film was strongly influenced by the adsorbed layer yielding a systematic increase in the dynamic Tg with decreasing the film thickness. However, at a thickness of ca. 30 nm, the influence of the mobile surface layer becomes more pronounced. This results in a systematic decrease in Tg with the further decrease of the film thickness, below 30 nm. These results were discussed with respect to thin films of PVME/PS blend with a composition of 50/50 wt.%as well as literature results. KW - Ultra thin polymer films PY - 2017 DO - https://doi.org/10.1063/1.4978505 SN - 0021-9606 SN - 1089-7690 VL - 146 IS - 20 SP - 203321-1 EP - 203321-9 PB - AIP Publishing AN - OPUS4-39558 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Madkour, Sherif A1 - Szymoniak, Paulina A1 - Heídari, M. A1 - von Klitzing, R. A1 - Schönhals, Andreas T1 - Unveiling the dynamics of self-assembled layers of thin films of poly(vinyl methyl ether) (PVME) by nanosized relaxation spectroscopy N2 - A combination of nanosized dielectric relaxation (BDS) and thermal spectroscopy (SHS) was utilized to characterize the dynamics of thin films of Poly(vinyl methyl ether) (PVME) (thicknesses: 7 nm – 160 nm). For the BDS measurements, a recently designed nano-structured electrode system is employed. A thin film is spin-coated on an ultra-flat highly conductive silicon wafer serving as the bottom electrode. As top electrode, a highly conductive wafer with non-conducting nanostructured SiO2 nano-spacers with heights of 35 nm or 70 nm is assembled on the bottom electrode. This procedure results in thin supported films with a free polymer/air interface. The BDS measurements show two relaxation processes, which are analyzed unambiguously for thicknesses smaller than 50 nm. The relaxation rates of both processes have different temperature dependencies. One process coincidences in its position and temperature dependence with the glassy dynamics of bulk PVME and is ascribed to the dynamic glass transition of a bulk-like layer in the middle of the film. The relaxation rates were found to be thickness independent as confirmed by SHS. Unexpectedly, the relaxation rates of the second process obey an Arrhenius-like temperature dependence. This process was not observed by SHS and was related to the constrained fluctuations in a layer, which is irreversibly adsorbed at the substrate with a heterogeneous structure. Its molecular fluctuations undergo a confinement effect resulting in the localization of the segmental dynamics. To our knowledge, this is the first report on the molecular dynamics of an adsorbed layer in thin films. KW - Broadband dielectric spectroscopy KW - AC-nanochip calorimetry KW - Nanostructured capacitors KW - Thin films PY - 2017 UR - http://pubs.acs.org/doi/pdf/10.1021/acsami.6b14404 DO - https://doi.org/10.1021/acsami.6b14404 SN - 1944-8244 VL - 9 IS - 8 SP - 7535 EP - 7546 PB - ACS Publications CY - Washington DC AN - OPUS4-39291 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Schönhals, Andreas T1 - Behavior of Ultra-Thin POLYMER Films investigated by Nanosized Relaxation Spectroscopy N2 - The glass transition behavior of ultra-thin polymer films is discussed in detail. Further nanosized relxation spectroscopy is introduced in the form of AC chip calorimetry and dielectric spectroscopy employing nanostructured electrodes. These methods arre applied to ultra-thin films. T2 - Soft Matter Seminar Jülich CY - Jülich, Germany DA - 15.12.2016 KW - Ultra-thin polymer films PY - 2016 AN - OPUS4-38714 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER -