TY - CONF A1 - Schönhals, Andreas T1 - Broadband Dielectric Spectroscopy and its Relationship to Other Spectroscopic Techniques T2 - Satelite Courses at 6. International Conference on Broadband Dielectric Spectroscopy and its Applications CY - Madrid, Spain DA - 2010-09-06 PY - 2010 AN - OPUS4-21977 LA - deu AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Wohlrab, Sebastian A1 - Schönhals, Andreas A1 - Goering, Harald A1 - Friedrich, Jörg Florian T1 - Integration of sol-gel derived inorganic nanonetworks into polymers N2 - Nanoparticulate networks as fillers for polymer based nanocomposites offer an optimized, surfactant free distribution of the inorganic component. Additionally, their non-aggregated but interconnected nanoparticulate subunits can lead to new properties owing to special inherent solid state properties and/or spacial restrictions to the polymeric parts. In particular, polymer nanocomposites based on poly(methyl methacrylate) (PMMA) or poly(hydroxyethyl methacrylate) (PHEMA), filled with different nanoparticulate networks of AlOOH were synthesized using two advanced synthesis techniques. An ex situ method, in which a preformed AlOOH-gel was solvent exchanged by methyl methacrylate (MMA) and an in situ method, in which the AlOOH scaffold was prepared within hydroxyethyl methacrylate (HEMA), have been used to produce the materials described here through polymerization. On the MMA based composites the particles were removed by etching, yielding porous polymers. Promising for a broad variety of crystallisable networks within polymers, the phase transition of amorphous AlOOH within PMMA towards crystalline boehmite was performed using a hydrothermal method. The materials were characterized using transmission electron microscopy, X-ray diffraction, gel permeation chromatography, differential scanning calorimetry, IR-spectroscopy, UV/Vis spectroscopy and hardness measurements. Special material properties were investigated using thermogravimetry, thermomechanical analysis and dynamic mechanical analysis. Furthermore, interactions between PMMA segments and the AlOOH network were detailed studied using dielectric spectroscopy. PY - 2010 DO - https://doi.org/10.1039/c0py00105h SN - 1759-9954 SN - 1759-9962 VL - 1 IS - 8 SP - 1226 EP - 1236 AN - OPUS4-21996 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Schönhals, Andreas A1 - Rittig, F. A1 - Kärger, J. T1 - Self-diffusion of poly(propylene glycol) in nanoporous glasses studied by pulsed field gradient NMR: A study of molecular dynamics and surface interactions N2 - Pulsed field gradient NMR is applied to investigate the self-diffusion of poly(proypylene glycol) in nanoporous glasses (nominal pore sizes of 2.5–7.5 nm). In general, the diffusion is slowed down by the confinement compared to the bulk. For native pore surfaces covered by hydroxyl groups the spin echo attenuation Ψ displays a bimodal behavior versus q2t (q-norm of a generalized scattering vector). This was explained assuming spatial regions of different diffusivities in a two-phase model. The slow component is assigned to segments forming a surface layer close to the pore walls in which the segments have a lower mobility than those located in the center of the pores. By variation of observation time it was concluded that time constant for the dynamic exchange of segments between these two regions is around 100 ms at room temperature. For silanized pores, the bimodal behavior in the spin echo attenuation Ψ shows a stretched exponential decay versus q2t. The estimated diffusion coefficients decrease strongly with decreasing pore size. The temperature dependence of the diffusion coefficient can be approximated by an Arrhenius law where the activation energy increases with decreasing pore size. The observed pore size dependence for the diffusion of poly(propylene glycol) in silanized nanoporous glasses can be discussed assuming interaction and confining size effects. KW - Glass KW - Molecular dynamics method KW - Nanoporous materials KW - Polymers KW - Self-diffusion KW - Spin echo (NMR) PY - 2010 DO - https://doi.org/10.1063/1.3479905 SN - 0021-9606 SN - 1089-7690 VL - 133 IS - 9 SP - 094903-1 - 094903-7 PB - American Institute of Physics CY - Melville, NY AN - OPUS4-22000 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Schönhals, Andreas T1 - Structure-Property Relationships of Polyolefine based Nanocomposites with Layered Double Hydroxides - Interplay between Matrix and Interfacial Effects T2 - 3. Jahresmeeting VAMA TWA-33 (Poymeric Nanocomposites) CY - Istanbul, Turkey DA - 2010-10-19 PY - 2010 AN - OPUS4-22228 LA - deu AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Frunza, S. A1 - Schönhals, Andreas A1 - Frunza, L. A1 - Ganea, P. A1 - Kosslick, H. A1 - Harloff, J. A1 - Schulz, A. T1 - Molecular relaxation processes in a MOF-5 structure revealed by broadband dielectric spectroscopy: signature of phenylene ring fluctuations N2 - The molecular mobility of a MOF-5 metal–organic framework was investigated by broadband dielectric spectroscopy. Three relaxation processes were revealed. The temperature dependence of their relaxation rates follows an Arrhenius law. The process observed at lower temperatures is attributed to bending fluctuations of the edges of the cages involving the Zn–O clusters. The processes ('region II') at higher temperatures were assigned to fluctuations of phenyl rings in agreement with the NMR data found by Gould et al. (J. Am. Chem. Soc. 2008, 130, 3246). The carboxylate groups might also be involved. The rotational fluctuations of the phenyl rings leading to the low frequency part of relaxation region II might be hindered either by some solvent molecules entrapped in the cages or by an interpenetrated structure and have a broad distribution of activation energies. The high frequency part of region II corresponds nearly to a Debye-like process: This is explained by a well-defined structure of empty pores. PY - 2010 DO - https://doi.org/10.1021/jp1071617 SN - 1520-6106 SN - 1520-5207 SN - 1089-5647 VL - 114 IS - 40 SP - 12840 EP - 12846 PB - Soc. CY - Washington, DC AN - OPUS4-22255 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Friedrich, Jörg Florian A1 - Mix, Renate A1 - Kühn, Gerhard A1 - Retzko, Iris A1 - Schönhals, Andreas A1 - Unger, Wolfgang T1 - Plasma-based introduction of monosort functional groups of different type and density onto polymer surfaces. Part 2: Pulsed plasma polymerization N2 - This new functionalization method consists of the deposition of very thin plasma polymer layers (20 to 100 nm) of functional group bearing monomers in pulsed plasma. With allylalcohol, a maximum of 30 OH groups per 100 C atoms was measured with a selectivity of about 90% and a significant stability at long-time exposure to air. Allylamine was used to produce primary amino groups, with a maximum of 18 NH2 groups per 100 C atoms. Side reactions were observed during the storage in air, such as oxidation of the amino groups. Carboxylic groups could be produced using acrylic acid with a maximum concentration of 24 COOH groups per 100 C atoms. The most prominent side reaction was the decarbonylation/ decarboxylation of the acid group during plasma deposition.___TAGSTART___BR___TAGEND___ The variation of the density of functional groups using the pulsed-plasma polymerization of functional-group-bearing monomers was possible by the chemically-initiated radical copolymerization with either a chain-extending monomer, such as ethylene, or a cross linker, such as butadiene, in plasma. The density of functional groups could be adjusted continuously (0 to 30 OH, 0 to 18 NH2 and 0 to 24 COOH groups per 100 C atoms).___TAGSTART___BR___TAGEND___ The successful application of these densely functionalized polymer surfaces for producing biocompatible surfaces and for use in metal–polymer composites is proposed. KW - Pulsed plasma polymerization KW - Plasma-initiated copolymerization KW - Charcterization of homo- and copolymers PY - 2003 DO - https://doi.org/10.1163/156855403765826874 VL - 10 IS - 2-3 SP - 173 EP - 223 PB - North-Holland CY - New York, NY AN - OPUS4-2706 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Schönhals, Andreas T1 - Behaviour of ploymers confined to nanoporous glasses studied by dielectric, thermal and vibrational spectroscopy: Cut - off length scale for glass transition? T2 - DPG-Frühjahrstagung (Polymerphysik), Fachverband CPP, Themenkreis 3 CY - Regensburg, Germany DA - 2002-03-11 PY - 2002 AN - OPUS4-3341 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Schönhals, Andreas T1 - The Behaviour of Polymers Confined to Nanoporous Glasses Investigated by Relaxation Experiment T2 - Polydays 2004 CY - Potsdam, Germany DA - 2004-10-04 PY - 2004 AN - OPUS4-4354 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Schönhals, Andreas T1 - Self-Diffusion of Poly(Propylene Glycol) Confined to Nanoporous Glasses by Pulsed Field Gradient NMR T2 - Polydays 2004 CY - Potsdam, Germany DA - 2004-10-04 PY - 2004 AN - OPUS4-4337 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Schönhals, Andreas T1 - Neutron Spectrocopy on Nanoconfined Polymers T2 - 7. International Conference on Quasi-Elastic Neutron Scattering CY - Arcachon, France DA - 2004-09-01 PY - 2004 AN - OPUS4-4318 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Schönhals, Andreas T1 - The Behaviour of Polymers confined to Nanoporous Glasses investigated by Relaxation Experiments T2 - Polydays 2004 CY - Potsdam, Germany DA - 2004-10-04 PY - 2004 AN - OPUS4-4319 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Schönhals, Andreas T1 - Neutron spectroscopy on polymers confined to nanoporous glasses T2 - Polydays 2004 CY - Potsdam, Germany DA - 2004-10-04 PY - 2004 AN - OPUS4-4320 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Zorn, R. A1 - Frick, B. A1 - Hartmann, L. A1 - Kremer, F. A1 - Schönhals, Andreas A1 - Richter, D. T1 - Dynamics of confined glass-forming systems observed by neutron scattering N2 - In this article, results on the microscopic dynamics of a low-molecular glass former and a polymer confined in nanoporous silica obtained by inelastic neutron scattering are presented. By combining time-of-flight spectroscopy and backscattering spectroscopy we are able to cover a large dynamical range, from the low-frequency vibrations to the relaxation. The most prominent effect was observed on the “boson peak” in the vibrational spectrum. A strong reduction of the modes at lowest frequencies could be observed in both cases. The main effect on the relaxation is a broadening for the salol system. For the polymeric system a difference of the confinement influence on the methyl-group rotation and the relaxation can be detected from a first qualitative interpretation of the data. T2 - 3rd European Conference on Neutron Scattering (ECNS-3) CY - Montpellier, France DA - 2003-09-03 KW - Glass transition KW - Confinement PY - 2004 DO - https://doi.org/10.1016/j.physb.2004.03.303 SN - 0921-4526 SN - 1873-2135 VL - 350 IS - 1-3 SP - e1115 EP - e1118 PB - North-Holland Physics Publ. CY - Amsterdam AN - OPUS4-4589 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Frunza, S. A1 - Frunza, L. A1 - Tintaru, M. A1 - Enache, I. A1 - Beica, T. A1 - Schönhals, Andreas T1 - Dynamics of the surface layer in cyanobiphenyl-aerosil nanocomposites with a high silica density N2 - Composites were prepared from an aerosil and 4-n-alkyl-4'cyanobiphenyls with five to eight carbon atoms in the alkyl chain. Their high silica density of sim7 g aerosil in 1 cm3 of liquid crystal (LC) allows the observation of the behaviour of a thin cyanobiphenyl layer (having nearly a monolayer structure) on the silica particles. The systems are investigated by dielectric spectroscopy (10-2-109 Hz) in a large temperature range (220-370 K). All the composites show a (main) relaxation process at frequencies much lower than the processes observed for the bulk LC that was assigned to the dynamics of the molecules in the surface layer. The temperature dependence of its characteristic frequencies obeys the Vogel-Fulcher-Tammann law, which is found to be typical for glass-forming liquids. The quasi two-dimensional character of the glass transition in the surface layer is discussed for the first time. At the nematic-to-isotropic transition temperature of the bulk, the composites show a continuous decrease of the characteristic frequencies as a function of the alkyl chain length, while the bulk LCs show the well known odd-even behaviour. The magnitude and temperature dependence of the slow relaxation process in the composites (molecules on an outer surface) agree with those of the same molecules confined to the nanopores of molecular sieves (internal surface). KW - Nanocomposite KW - Surface Layer KW - Liquid Crystals Dielectric Spectroscopy PY - 2004 DO - https://doi.org/10.1080/02678290410001675147 SN - 0267-8292 SN - 1366-5855 VL - 31 IS - 7 SP - 913 EP - 922 PB - Taylor & Francis CY - London AN - OPUS4-4709 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Schönhals, Andreas T1 - Water relaxation behavior inside the pores and cages of some molecular sieves T2 - International Workshop on Dynamics in Confinement CY - Grenoble, France DA - 2003-01-23 PY - 2003 AN - OPUS4-4656 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Schönhals, Andreas T1 - Molecular dynamics of 4n-octycyanobiphenyl confined to nanoporous SBA molecular sieves T2 - International Workshop on Dynamics in Confinement CY - Grenoble, France DA - 2003-01-23 PY - 2003 AN - OPUS4-4657 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Schönhals, Andreas T1 - Polymers in Nono-Confinemnets: What can we learn from relaxation and scattering experiments? T2 - 14th Wolfgang-Ostwald-Colloquium CY - Berlin, Germany DA - 2004-11-22 PY - 2004 AN - OPUS4-5707 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Schönhals, Andreas T1 - Polymers in Nanopores: Comparison of Relaxation and Scattering Experiments T2 - Arbeitsgruppentreffen Polymerphysik CY - Großbothen, Germany DA - 2004-12-05 PY - 2004 AN - OPUS4-5708 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Frunza, L. A1 - Kosslick, H. A1 - Pitsch, I. A1 - Frunza, St. A1 - Schönhals, Andreas T1 - Rotational Fluctuations of Water inside the Nanopores of SBA-Type Molecular Sieves N2 - The rotational molecular dynamics of water confined to nanoporous molecular sieves of a regular hexagonal (SBA-15) and of a foamlike pore structure was studied by dielectric spectroscopy in the frequency range from 10-2 to 109 Hz and in a broad temperature interval. Two relaxation processes were observed: the process at lower frequencies is related to water molecules forming a layer, which is strongly adsorbed at the pore surface, whereas the relaxation process at higher frequencies is assigned to fluctuations of water molecules situated close to the center of the pore. The relaxation times of the low-frequency process for both materials and of the high-frequency process for the SBA-15 material have an unusual saddlelike temperature dependence, reported here for the first time. To describe this temperature dependence, a model developed for water confined to nanoporous glasses by Ryabov et al. [J. Phys. Chem. B 2001, 105, 1845] was applied, which considers two competing effects. The characteristic features of these two competing processes were compared with those reported for other porous systems. PY - 2005 DO - https://doi.org/10.1021/jp044503t SN - 1520-6106 SN - 1520-5207 SN - 1089-5647 VL - 109 IS - 18 SP - 9154 EP - 9159 PB - Soc. CY - Washington, DC AN - OPUS4-7611 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Schönhals, Andreas T1 - Dielectric and thermal spectroscopy on polymers confined to nanoporous glasses T2 - 5th International Discussion Meeting on Relaxations in Complex Systems, New results, Directions and Opportunities CY - Lille, France DA - 2005-07-07 PY - 2005 AN - OPUS4-7661 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Schönhals, Andreas T1 - Neutron spectroscopy on polymers confined to nanoporous glasses T2 - Jahrestagung der Deutschen Physikalischen Gesellschaft, Fachverband Polymerphysik und Chemische Physik CY - Berlin, Germany DA - 2005-03-04 PY - 2005 AN - OPUS4-7776 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Schönhals, Andreas T1 - Molecular Dynamics of Polymers Confined to Nanoporous Glasses T2 - Frühjahrstagung der Amerikanischen Chemischen Gesellschaft CY - San Diego, CA, USA DA - 2005-03-13 PY - 2005 AN - OPUS4-7778 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - GEN A1 - Schönhals, Andreas ED - Grellmann, W. ED - Seidler, S. T1 - Elektrische und dielektrische Eigenschaften KW - Elektrische Eigenschaften KW - Dielektrische Eigenschaften KW - Kunststoffe PY - 2005 SN - 3-446-22086-0 SP - 352 EP - 395 PB - Hanser CY - München AN - OPUS4-10530 LA - deu AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Hakme, C. A1 - Stevenson, I. A1 - David, L. A1 - Boiteux, G. A1 - Seytre, G. A1 - Schönhals, Andreas T1 - Uniaxially stretched poly(ethylene naphthalene 2,6-dicarboxylate) films studied by broadband dielectric spectroscopy N2 - The thermal behaviors of amorphous PEN films uniaxially stretched above and below Tg have been characterized by Temperature Modulated DSC. When drawing is performed above Tg, the degree of crystallinity and the glass transition temperature Tg increase with increasing drawing ratio. PEN samples stretched below Tg are more crystalline than when stretched above Tg. Moreover the cold crystallization phenomenon disappears with drawing as a result of the mechanically induced crystallization. Broadband dielectric spectroscopy has also been used to study the influence of the orientation on the molecular mobility of PEN to gain insight into the microscopic origin of the relaxation processes in the transverse direction i.e. when the electric field is perpendicular to the stretching direction. Dielectric relaxation phenomena are thus discussed as a function of the microstructure (orientation, crystallinity). The α-relaxation dynamics associated with the glass transition are largely slowed down by the drawing process and the relaxation strength decreases. This can be related to a transformation of the amorphous phase into (i) crystalline, (ii) rigid amorphous fraction (RAF) and/or constrained amorphous phase with lower molecular mobility due to the crystallization induced by the orientation process. In contrast, the dynamics of the ß*-relaxation are apparently increased and the activation energy for the uniaxially stretched samples decreases compared to the unstretched isotropic amorphous state. If the ß*-relaxation is assigned to the presence of naphthalene aggregates, this leads to the conclusion that stretching is structurally altering the naphthalene aggregates (creation of defective aggregates that induces a higher molecular mobility) or orientation is selecting the faster motions active for ß*. The ß-relaxation which corresponds to more local motions implying reorientation of the ester groups seems to be broad and composed of two components as in the case of PET: the ß1- and ß2-relaxations. While the high frequency ß1-component relaxation strength is increasing significantly with the deformation below Tg, that of the ß2-process is more related to the presence of water. KW - Poly(ethylene 2,6-naphthalene-dicarboxylate) KW - Dielectric Relaxation Spectroscopy (DRS) KW - TMDSC PY - 2005 DO - https://doi.org/10.1016/j.jnoncrysol.2005.05.039 SN - 0022-3093 VL - 351 IS - 33-36 SP - 2742 EP - 2752 PB - North-Holland Publ. Co. CY - Amsterdam AN - OPUS4-10855 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Schönhals, Andreas A1 - Goering, Harald A1 - Schick, Ch. A1 - Frick, b. A1 - Zorn, R. T1 - Polymers in nanoconfinement: What can be learned from relaxation and scattering experiments? N2 - Dielectric spectroscopy in combination with temperature modulated differential scanning calorimetry and quasielastic/inelastic neutron scattering are employed to investigate the molecular (glassy) dynamics of poly(dimethyl siloxane) (PDMS) and poly(methyl phenyl siloxane) (PMPS) confined to random nanoporous glasses with nominal pore sizes between 2.5 nm and 20 nm. Inside the pores PDMS and PMPS have faster molecular dynamics than in the bulk state. Down to a pore size of 7.5 nm the temperature dependence of the relaxation times (or rates) obeys the Vogel/Fulcher/Tammann (VFT) equation where the data obtained from dielectric and thermal spectroscopy agree quantitatively. At a pore size of 5 nm this VFT-like temperature dependence changes to an Arrhenius behavior. At the same confining length scale the increment of the specific heat capacity at Tg normalized to the weight of the confined polymer vanishes. The results indicate that a minimal length scale seems to be relevant for glassy dynamics in both polymers although the estimated length scale of about 5 nm seems to a bit too large in comparison to other experimental results and theoretical approaches. Neutron scattering is employed to investigate methyl group reorientation and the fast segmental dynamics of both polymers in confinement. Although the methyl group rotation is a localized process these experiments show that a part of the methyl groups is immobilized by the confinement whereas the effects for PDMS are much more pronounced than for PMPS. With regard to the segmental dynamics, neutron scattering reveals a big difference in the behavior of both polymers. Whereas the data obtained for PMPS are in accord with a boundary layer formed at the surfaces of the nanopores, for PDMS a considerable amount of elastic scattering is observed. To explain this result it is assumed that some structure formation of PDMS takes place in the nanopores, although the thermal data show no crystallization or melting effects. KW - Glass transition KW - Dielectric loss and relaxation KW - Macromolecular and polymer solutions KW - Polymer melts KW - Swelling PY - 2005 DO - https://doi.org/10.1016/j.jnoncrysol.2005.03.062 SN - 0022-3093 VL - 351 IS - 33-36 SP - 2668 EP - 2677 PB - North-Holland Publ. Co. CY - Amsterdam AN - OPUS4-10856 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Frick, B. A1 - Alba-Simionesco, C. A1 - Dosseh, G. A1 - Le Quellec, C. A1 - Moreno, A. J. A1 - Colmenero, J. A1 - Schönhals, Andreas A1 - Zorn, R. A1 - Chrissopoulou, K. A1 - Anastasiadis, S. H. A1 - Dalnoki-Veress, K. T1 - Inelastic neutron scattering for investigating the dynamics of confined glass-forming liquids N2 - Inelastic neutron scattering was employed over recent years to investigate the influence of spatial confinement on the dynamics of glass-forming systems. We review the common phenomena observed by neutron scattering in such different confining hosts like porous glasses, molecular sieves, clays or free standing polymer films, which impose a spatial limitation to the motion of small organic molecules, oligomers or polymers. Near the glass transition temperature the mean squared displacements of the confined molecules show clear deviations from the bulk behavior. The observed increase or decrease of the mean squared displacements confirms the high relevance of the interface interaction near walls of confining media without excluding additional real confinement effects. We show a new comparison of the mean squared displacement for PDMS and PMPS in bulk and in different type of restricting geometries, which evidence a weak influence of the restricting geometry on the local methyl group motion, but a strong influence on the glass transition dynamics, if wall interactions are taken into account. Strong wall interaction is also supported by the intermediate scattering function, measured either by combining neutron backscattering and time-of-flight experiments to cover 3 decades in time from ns to ps or by neutron spin echo, which reveal above Tg an increasing elastic fraction with decreasing pore size and a slowing down of the dynamics. Furthermore we show that a reduction of modes below the Boson peak frequency is a more general feature of confined glass-forming systems. PY - 2005 DO - https://doi.org/10.1016/j.jnoncrysol.2005.03.061 SN - 0022-3093 VL - 351 IS - 33-36 SP - 2657 EP - 2667 PB - North-Holland Publ. Co. CY - Amsterdam AN - OPUS4-10831 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Hardy, L. A1 - Stevenson, I. A1 - Fritz, A. A1 - Boiteux, G. A1 - Seytre, G. A1 - Schönhals, Andreas T1 - Dielectric and dynamic mechanical relaxation behaviour of poly(ethylene 2,6-naphthalene dicarboxylate). II. Semicrystalline oriented films N2 - The dielectric and dynamic mechanical behaviour of bi-stretched non-treated and annealed semicrystalline poly(ethylene 2,6-naphthalene dicarboxylate) (PEN) films are studied as a function of different morphologies obtained by thermal treatments at temperatures close to the melting temperature of a semicrystalline film. Differential scanning calorimetry (DSC) shows that the glass transition temperatures do not change significantly with the thermal treatment for bi-stretched films. However, the melting temperatures and the degree of crystallinity increase with the value of annealing temperature. Both dielectric relaxation spectroscopy (DRS) and dynamic mechanical analysis (DMA) display three relaxation processes. In order of decreasing temperature, can be observed: the ?-relaxation due to the glass transition, the ?*-process assigned to cooperative molecular motions of the naphthalene groups which aggregate and the ?-relaxation due to local fluctuations of the carbonyl groups. The ?-relaxation process shifts to higher temperatures for the 250 and 260 °C treated bi-stretched semicrystalline samples compared to the sample thermally treated at 240 °C according to DRS data but shifts to lower temperatures according to the DMA measurements for the three annealed samples. This discrepency results from the different sensitivity of each methods with regards to the release of orientation. At a fixed frequency the temperature associated to ?*-relaxation is lower for the non-treated bi-stretched semicrystalline samples than for the treated ones using DMA but no difference can be seen in DRS. The associated apparent activation energies are rather high which suggest cooperative motions. It is assumed that the orientation of the samples prevents coupling between the naphthalene groups due to the stretched chain configuration in the amorphous phase. The activation energy for the ?-process given by DRS is independent of the thermal treatment and the value agrees with those found for poly(ethylene terephthalate) (PET) and amorphous PEN. Evidence of the decrease of orientation in the sample with thermal treatment can be seen via the onset of mobility, both by DRS and DMA. Thus, the orientation induces a greater change of properties compared to the crystalline samples obtained from the thermal treatment of an amorphous sample. Finally, a three phase model is proposed since there is evidence of a rigid amorphous phase present in PEN biaxially stretched samples which was favoured by the dependence of dielectric relaxation strengths on the degree of crystallinity for the ?*- and ?-relaxation. KW - Dielectric relaxation spectroscopy KW - Dynamic mechanical analysis KW - Poly(ethylene 2,6-naphthalene dicarboxylate) PY - 2003 DO - https://doi.org/10.1016/S0032-3861(03)00332-X SN - 0032-3861 SN - 1873-2291 VL - 44 IS - 15 SP - 4311 EP - 4323 PB - Springer CY - Berlin AN - OPUS4-2604 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - GEN A1 - Simon, G. P. A1 - Schönhals, Andreas ED - Simon, G. P. T1 - Dielectric Relaxation and Thermal Stimulated Currents PY - 2003 SN - 0-8412-3818-9 SP - 96 EP - 130 PB - American Chemical Society CY - Washington, DC AN - OPUS4-2615 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Schönhals, Andreas T1 - Confinement of nematic liquid crystals in SBA mesoporous materials T2 - 2nd International Feza (Federation of the European Zeolite Associations) Conference CY - Taormina, Italy DA - 2002-09-01 PY - 2002 AN - OPUS4-3558 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - GEN A1 - Schönhals, Andreas A1 - Goering, Harald A1 - Schick, C. A1 - Frick, B. A1 - Zorn, R. ED - Fourkas, J. T. T1 - Poly(methyl phenyl siloxane) in random nanoporous glasses - molecular dynamics and structure N2 - The effect of a nanometer confinement on the molecular dynamics of poly(methyl phenyl siloxane) (PMPS) was studied by dielectric spectroscopy (DK), temperature modulated DSC (TMDSC) and neutron scattering (NS). DK and TMDSC experiments show that for PMPS in 7.5 nm pores the molecular dynamics is faster than in the bulk which originates from an inherent length scale of the underlying molecular motions. At a pore size of 5 nm the temperature dependence of the relaxations times changes from a Vogel-Fulcher-Tammann like behavior to an Arrhenius one. At the same pore size Dcp vanishes. These results give strong support that the glass transition has to be characterized by an inherent length scale of the relevant molecular motions. Quasielastic neutron scattering experiments reveal a strong change even in the microscopic dynamic. T2 - Symposium P: "Dynamics in Small Confining Systems VII" ; MRS fall meeting 2004 CY - Boston, MA, USA DA - 2003-12-01 KW - Nanometer Confinement KW - Dielectric and thermal spectroscopy KW - Neutron scattering KW - Poly(methyl phenyl siloxane) PY - 2004 SN - 1-558-99728-8 DO - https://doi.org/10.1557/PROC-790-P9.3 SN - 0272-9172 N1 - Serientitel: Materials Research Society symposium proceedings – Series title: Materials Research Society symposium proceedings IS - 790 SP - P9.3.1 EP - P9.3.6 PB - Materials Research Society CY - Warrendale, Pa. AN - OPUS4-3520 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Schönhals, Andreas A1 - Goering, Harald A1 - Schick, C. A1 - Frick, B. A1 - Zorn, R. T1 - Glass transition of polymers confined to nanoporous glasses N2 - The glassy dynamics of poly(propylene glycol) (PPG) and poly(methyl phenyl siloxane) (PMPS) confined to nanoporous glasses (pore sizes 2.5–20 nm) investigated by dielectric spectroscopy, temperature modulated DSC and neutron scattering is compared. For both systems the relaxation rates estimated from dielectric spectroscopy and temperature modulated DSC agree quantitatively indicating that both experiments sense the glass transition. For PPG the glassy dynamics in nanopores is determined by a counterbalance of an adsorption and a confinement effect where the temperature dependence of the relaxation times obeys the Vogel/Fulcher/Tammann (VFT-) equation. The former effect results from an interaction of the confined macromolecules with the internal surfaces which in general slows down the molecular dynamics. A confinement effect leads to an acceleration of the segmental dynamics compared to the bulk state and points to an inherent length scale on which the glassy dynamics takes place. The step of the specific heat capacity Deltacp at the glass transition vanishes at a finite length scale of 1.8 nm. This result supports further the conception that a characteristic length scale is relevant for glassy dynamics. For PMPS down to a pore size of 7.5 nm the temperature dependence of the relaxation times follows the VFT-dependence and a confinement effect is observed like for PPG. At a pore size of 5 nm this changes to an Arrhenius-like behavior with a low activation energy. At the same pore size Deltacp vanishes for PMPS. This points to a dramatic change in the character of molecular motions responsible for glassy dynamics and supports further the relevance of a characteristic length scale on which it takes place. Quasielastic neutron scattering experiments on PMPS reveal that the microscopic dynamics characterized by the mean square displacement depends on confinement above the glass transition. The diffusive character of the relevant molecular motions seems to disappear at a length scale of about 1.6 nm. KW - Glass transition KW - Polymers KW - Nanoporous glasses KW - Glassy dynamics KW - Poly(propylene glycol) KW - Poly(methyl phenyl siloxane) PY - 2004 DO - https://doi.org/10.1007/s00396-004-1106-3 SN - 0303-402X SN - 1435-1536 VL - 282 SP - 882 EP - 891 PB - Springer CY - Berlin AN - OPUS4-3630 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Schönhals, Andreas T1 - Dielectric Investigations under Irradiation of Photochromic Copolymers with Azobenzene Moieties in the Side Group T2 - 7th International Symposium Polymers for Advanced Technologies CY - Fort Lauderdale, FL, USA DA - 2003-09-21 PY - 2003 AN - OPUS4-4666 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Schönhals, Andreas A1 - Goering, Harald A1 - Schick, C. T1 - Segmental Dynamics of Polymeric Liquids Confined to Nanoporous Glasses T2 - ACS 2002 Biennial Symposium "Polymeric Nanomaterials" CY - Rohnert Park, CA, USA DA - 2002-11-17 PY - 2002 AN - OPUS4-2055 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Turky, Gamal A1 - Schönhals, Andreas T1 - Influence of azobenzene concentration on the dielectric behavior of amorphous comb-like copolymers with photochromic azobenzene side groups T2 - 2nd International Conference on Broadband Dielectric Spectroscopy and Its Applications CY - Leipzig, Germany DA - 2002-09-02 PY - 2002 AN - OPUS4-2056 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Schönhals, Andreas T1 - Molecular dynamics and structure of molecules in confining geometries - A comparison of relaxation and scattering techniques T2 - 2nd International Conference on Broadband Dielectric Spectroscopy and Its Applications CY - Leipzig, Germany DA - 2002-09-02 PY - 2002 AN - OPUS4-2039 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Schönhals, Andreas A1 - Goering, Harald A1 - Brzezinka, Klaus-Werner A1 - Schick, C. T1 - Molecular dynamics of polymers in random nanometer confinements investigated by relaxational scattering techniques N2 - Dielectric spectroscopy and temperature-modulated differential scanning calorimetry are employed to study the molecular dynamics of oligomeric poly(propylene glycol) (PPG) melts of different molecular weights confined to nanoporous glasses (pore sizes 2.5, 5.0, 7.5 and 20 nm). Moreover, the results obtained for the polymers are compared with those for the corresponding monomer. The experimental results are discussed in the framework of the interplay of confinement and adsorption effects. For large pore sizes (> 5 nm) a speeding up of the molecular dynamics is observed (the confinement effect), whereas for small pore sizes (< 5 nm) a slowing down of the segmental fluctuations is found (the adsorption effect). In addition, a minimal length scale for the glass transition of 1.6 nm is estimated for PPG confined in nanoporous glasses. This supports the idea that the molecular motions responsible for the glassy dynamics must be describable by a characteristic length scale. Polarized Raman scattering investigations are carried out to investigate the conformations of the macromolecules inside the pores. These experiments show that the confined polymer chains are locally stretched. This effect increases with decreasing pore size. T2 - 3rd Workshop on Non-Equilibrium Phenomena in Supercooled Fluids, Glasses and Amorphous Materials CY - Pisa, Italy DA - 2003-09-22 PY - 2003 DO - https://doi.org/10.1088/0953-8984/15/11/334 SN - 0953-8984 SN - 1361-648X VL - 15 IS - 11 SP - S1139 EP - S1148 PB - IOP Publ. Ltd. CY - Bristol AN - OPUS4-2041 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Schönhals, Andreas T1 - Polar Molecules in Nanoporous Confinements T2 - Workshop "Glasübergang" CY - Rostock, Germany DA - 2002-12-16 PY - 2002 AN - OPUS4-2042 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Schönhals, Andreas A1 - Goering, Harald A1 - Brzezinka, Klaus-Werner A1 - Schick, Ch. T1 - The molecular dynamics of polymers in random nanometre confined spaces investigated by relaxational and scattering techniques PY - 2003 SN - 0953-8984 SN - 1361-648X VL - 15 SP - S1139 EP - S1148 PB - IOP Publ. Ltd. CY - Bristol AN - OPUS4-2463 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Frunza, L. A1 - Kosslick, H. A1 - Bentrup, U. A1 - Pitsch, I. A1 - Fricke, R. A1 - Frunza, S. A1 - Schönhals, Andreas T1 - Surface layer in composites containing 4-n-octyl-4'-cyanobiphenyl. FTIR spectroscopic characterization N2 - Composites containing 4-n-octyl-4?-cyanobiphenyl (8CB) either confined to nanopores of molecular sieves with very large pores or coating silica nanoparticles of aerosil type at high silica-to-8CB ratios are investigated by IR spectroscopy. Band shape analysis was performed in wavenumber regions in which the peaks due to CN stretching, CH stretching and CH out-of-plane vibrations appear. Some of molecules confined to molecular sieves show spectroscopic features characteristic to a bulk-like 8CB matter located in the centre of the pores or in the inter-grain space. Other features of the IR spectra are due to 8CB molecules located in the surface layer, mostly forming hydrogen bonds between their CN groups and surface OH groups. Another part of the 8CB molecules in the surface layer may also interact by ? electrons of the aromatic rings. Hydrogen bonding is less hindered for the molecules of the surface layers onto aerosil particles than inside pores of the molecular sieves. Comparison is also made with the case of composites based on molecular sieves with small pores. KW - Surface layer KW - Cyanobiphenyls KW - Infrared spectroscopy KW - Band shape analysis PY - 2003 DO - https://doi.org/10.1016/S0022-2860(03)00110-8 SN - 0022-2860 SN - 1872-8014 SN - 0377-046X VL - 651-653 SP - 341 EP - 347 PB - Elsevier CY - Amsterdam AN - OPUS4-2795 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Frunza, S. A1 - Kosslick, H. A1 - Schönhals, Andreas A1 - Frunza, L. A1 - Enache, I. A1 - Beica, T. T1 - Study of the surface layer of aerosil-8CB composites by TG/DTA/DSC measurements N2 - Thermal analysis measurements were applied to study the behavior of composite systems containing a nematic liquid crystal (LC), 4-n-octyl-4?-cyanobiphenyl (8CB) and aerosil particles. The silica density ?s (g of silica per 1 cm3 of LC) was varied from 0.20 to 12 g/cm3 in order to approach the monomolecular structure of the surface layer. Thus, thermogravimetric (TG) measurements were performed to get information on the LC content of the samples. Moreover, they allowed an unusual application, to characterize the interaction of 8CB molecules with aerosil surface because the corresponding curves show multistep processes the temperatures of which depend on the silica density. Differential thermal analysis (DTA) also indicates several processes. Some of them, mostly due to desorption, are endothermal. Other processes are exothermal, and these are assigned to chemical transformations. The sample with silica density of 12 g/cm3 has no endothermal desorption peak at low temperatures, and has the highest shift for the DTA peaks. It was supposed that its surface layer has a monomolecular structure. For representative samples, TG–DTA studies were supported by FTIR investigations. Thus conventional TG–DTA techniques have provided new tools to characterize the nanocomposites. Differential scanning calorimetry gives the behavior of the phase transitions. Samples with low silica density exhibit a depression of the phase transition temperatures characteristic for the bulk 8CB while those with high silica densities do not show any phase transitions. PY - 2003 DO - https://doi.org/10.1016/S0022-3093(03)00319-3 SN - 0022-3093 VL - 325 IS - 1-3 SP - 103 EP - 112 PB - North-Holland Publ. Co. CY - Amsterdam AN - OPUS4-2796 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Schönhals, Andreas A1 - Floudas, G. A1 - Mierzwa, M. T1 - Temperature and pressure dependence of the dynamics in a poly(methyl acrylate) side-chain liquid-crystalline polymer N2 - The molecular dynamics of a side-chain polymer liquid crystal with a poly(methyl acrylate) backbone and a (p-alkoxy-phenyl)-benzoate mesogenic group have been studied in the unaligned state as a function of temperature and pressure using dielectric spectroscopy. Polarizing optical microscopy, differential scanning calorimetry, and pressure-volume-temperature (PVT) measurements revealed three transition temperatures separating four phases (glass, smectic, nematic, and isotropic). Different dynamic processes have been identified reflecting librational modes (? process), local relaxation of the mesogenic group (? process), the segmental mode (? process) associated with the dynamic glass transition, and a slower process (? process) reflecting the side-chain dynamics within the liquid crystal order. Pressure exerts a stronger influence on the ? as compared to the ? process. Starting from the nematic phase, pressure was found to induce the nematic-to-smectic transformation. The associated dynamic changes were in excellent agreement with the PVT results implying that the dynamics are directly coupled to the thermodynamic state. Pressure was found to enhance the stability of the smectic order within the P-T phase diagram. PY - 2003 DO - https://doi.org/10.1103/PhysRevE.67.031705 SN - 1539-3755 SN - 1063-651X VL - 67 IS - 3 SP - 031705-1-031705-8 PB - American Institute of Physics CY - Melville, NY AN - OPUS4-2800 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Schönhals, Andreas A1 - Frunza, Ligia A1 - Kosslick, H. A1 - Frunza, Stefan A1 - Fricke, R. T1 - On the mobility of sodium ions and of confined liquid crystals in faujasite 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 15.12 SP - 438 CY - Bad Honnef AN - OPUS4-2262 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Schönhals, Andreas A1 - Frunza, Ligia A1 - Frunza, Stefan A1 - Bentrup, U. A1 - Fricke, R. A1 - Pitsch, I. A1 - Kosslick, H. T1 - Confinement of nematic liquid crystals in SBA mesoporous materials N2 - This work presents some results obtained by confining octylcyanobiphenyl (8CB) to the pores of two SBA-15 type host materials: a silica SBA-15 (pores of 10.2 nm) and an aluminum containing AlSBA-15 (pores of 7.5 nm). The LC molecules were loaded inside the pores from a solution in acetone, in a percentage higher than 70% from the maximum possible loading. It was observed that the 8CB molecules confined to molecular sieves may preserve the phase transitions characteristic for the bulk LC provided that the confining pores are sufficiently large, as offered by SBA materials. However, present guest-host interactions play an important role in these phase transitions. Such a behavior is at variance with the 8CB confined to Controlled Porous Glass with the same pore dimensions, for which the bulk-like phase transitions can be always observed. T2 - 2nd International FEZA conference CY - Taormina, Italy DA - 2002-09-01 PY - 2002 DO - https://doi.org/10.1016/S0167-2991(02)80296-8 SN - 0167-2991 VL - 142 IS - 2 SP - 1323 EP - 1329 PB - Elsevier CY - Amsterdam AN - OPUS4-2263 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Schönhals, Andreas A1 - Frunza, Ligia A1 - Kosslick, H. A1 - Pitsch, I. A1 - Frunza, Stefan T1 - Molecular dynamics of 4n-octylcyanobiphenyl confined to nanoporous molecular sieves of SBA-type T2 - International Conference of Dielectric Spectroscopy CY - Leipzig, Germany DA - 2002-09-01 PY - 2002 SP - 1(?) AN - OPUS4-2264 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Schönhals, Andreas A1 - Frunza, Ligia A1 - Frunza, Stefan A1 - Kosslick, H. T1 - Unusual relaxation behavior of water inside the sodalite cages of faujasite-type molecular sieves T2 - International Conference of Dielectric Spectroscopy CY - Leipzig, Germany DA - 2002-09-01 PY - 2002 SP - 1(?) AN - OPUS4-2265 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Schönhals, Andreas A1 - Frunza, Stefan A1 - Frunza, Ligia T1 - Dinamica compozitelor aerosil - 8CB prin spectroscopie dielectrica; On the dynamics of aerosil - 8CB composites by dielectric spectroscopy T2 - Romanian Annual Conference 2002 CY - Târgu Mure¸s, Romania DA - 2002-09-01 PY - 2002 SP - 1(?) AN - OPUS4-2266 LA - ron AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Schönhals, Andreas A1 - Frunza, Stefan A1 - Kosslick, H. A1 - Frunza, Ligia A1 - Enache, I. A1 - Beica, T. T1 - Studiul stratului de suprafata pe compozite aerosil - 8CB prin analiza termica / Study of surface layer in 8CB-aerosil composites by TG/DTA/TG measurements T2 - Annual Session of Romanian Research Program CERES CY - Bucharest, Romania DA - 2002-11-28 PY - 2002 AN - OPUS4-2267 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Schönhals, Andreas A1 - Frunza, Ligia A1 - Kosslick, H. A1 - Pitsch, I. A1 - Fricke, R. A1 - Bentrup, U. A1 - Frunza, Stefan T1 - Nanoporous materials as hosts for liquid crystals T2 - DFG-Workshop on Key Program "Nanoporous Crystals" CY - Berlin, Germany DA - 2002-10-21 PY - 2002 SP - 1(?) AN - OPUS4-2268 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Schönhals, Andreas A1 - Frunza, S. A1 - Frunza, L. A1 - Goering, Harald T1 - On the dynamics of the surface layer in octylcynobiphenyl-aerosil nanocomposites 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 15.11 SP - 438 CY - Bad Honnef AN - OPUS4-2269 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Schönhals, Andreas A1 - Frunza, Ligia A1 - Kosslick, H. A1 - Bentrup, U. A1 - Pitsch, I. A1 - Fricke, R. A1 - Frunza, Stefan ED - Barnes, A. J. T1 - First spectroscopic characterization of the surface layer in composites containing liquid crystals confined to nanopores T2 - 26th European Congress on Molecular Spectroscopy (EUCMOS) CY - Villeneuve-d'Ascq, France DA - 2002-09-01 KW - Liquid crystals KW - Confinement KW - Surface layer KW - Infrared spectroscopy KW - Band shape analysis PY - 2002 SN - 0022-2860 VL - 651-653 SP - 1(?) EP - 14(?) PB - Elsevier CY - Amsterdam AN - OPUS4-2270 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Schönhals, Andreas A1 - Goering, Harald A1 - Schick, C. A1 - Frick, B. A1 - Zorn, R. T1 - Glassy dynamics of polymers confined to nanoporous glasses revealed by relaxational and scattering experiments N2 - The glassy dynamics of poly(propylene glycol) (PPG) and poly(dimethyl siloxane) (PDMS) confined to a nanoporous host system revealed by dielectric spectroscopy, temperature-modulated DSC and neutron scattering is compared. For both systems the relaxation rates estimated from dielectric spectroscopy and temperature-modulated DSC agree quantitatively indicating that both experiments sense the glass transition. For PPG the segmental dynamics is determined by a counterbalance of adsorption and confinement effect. The former results form an interaction of the confined macromolecules with the internal surfaces. A confinement effect originates from an inherent length scale on which the underlying molecular motions take place. The increment of the specific-heat capacity at the glass transition vanishes at a finite length scale of 1.8 nm. Both results support the conception that a characteristic length scale is relevant for glassy dynamics. For PDMS only a confinement effect is observed which is much stronger than that for PPG. Down to a pore size of 7.5 nm, the temperature dependence of the relaxation times follows the Vogel-Fulcher-Tammann dependence. At a pore size of 5 nm this changes to an Arrhenius-like behaviour with a low activation energy. At the same pore size vanishes for PDMS. Quasielastic neutron scattering experiments reveal that also the diffusive character of the relevant molecular motions --found to be characteristic above the glass transition-- seems to disappear at this length scale. These results gives further strong support that the glass transition has to be characterised by an inherent length scale of the relevant molecular motions. KW - Glass transitions KW - Dielectric loss and relaxation KW - Macromolecular and polymer solutions KW - Polymer melts KW - Swelling PY - 2003 DO - https://doi.org/10.1140/epje/i2003-10036-4 SN - 1292-8941 SN - 1292-895X VL - 12 IS - 1 SP - 173 EP - 178 PB - EDP Sciences CY - Orsay AN - OPUS4-2866 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Turky, Gamal A1 - Schönhals, Andreas T1 - Influence of azobenzene concentration on the dielectric behavior of amorphous comb-like copolymers with photochromic side groups N2 - Dielectric spectroscopy in the frequency range from 10-2 to 106 Hz and in the temperature range from 190 to 440 K is employed to study the effect of azobenzene concentration on the dielectric relaxation processes of an amorphous comb-like copolymethacrylate. Four concentrations (x=29, 45.5, 54, and 74.5 mol%) of photochromic group 4-amino-azobenzene were investigated, where as comonomer a methacrylate unit having a derivative of benzanilide in the side group is used. Two prominent processes, the ?-relaxation at low temperatures which is related to rotational fluctuations of the mesogenic unit around its long axes and the dynamic glass transition (?-relaxation, segmental dynamics) at higher temperatures are observed for all azobenzene concentrations. In addition in between the ?- and the ?-relaxation a ??-process is observed for the polymers with the two lowest azobenzene concentrations, which seems to be related to the azobenzene unit. The dependence of the dielectric strength and the relaxation rate of the relaxation processes on the azobenzene concentration is discussed and interpreted in a simple phenomenological model, where also data obtained by semi empirical quantum chemical calculations are used. KW - Azobenzene KW - comb-like copolymer KW - Dielectric relaxation KW - Mesogenic unit PY - 2004 DO - https://doi.org/10.1016/j.polymer.2003.10.063 SN - 0032-3861 SN - 1873-2291 VL - 45 IS - 1 SP - 255 EP - 262 PB - Springer CY - Berlin AN - OPUS4-2867 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Schönhals, Andreas T1 - The behavior of polymers confined to nanoporous glasses investigated by dielectric, thermal and neutron spectroscopy T2 - Vortrag an der Universität Toulouse "Paul Sabatier" CY - Toulouse, France DA - 2004-07-21 PY - 2004 AN - OPUS4-3900 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Schönhals, Andreas T1 - Dynamics of surface layer in cyanobiphenyl-aerosil nanocompositeswith a high silica density T2 - 3th International Conference on Broadband Dielectric Spectroscopy and its Applications CY - Delft, Netherlands DA - 2004-08-23 PY - 2004 AN - OPUS4-3902 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Schönhals, Andreas T1 - Polymers in Nanoconfinements - What can we learn from relaxation and scattering experiments? T2 - 3th International Conference on Broadband Dielectric Spectroscopy and its Applications CY - Delft, Netherlands DA - 2004-08-23 PY - 2004 AN - OPUS4-3904 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Schönhals, Andreas T1 - Polymers in Random Nanoporous Glasses: Molecular dynamics and Structure T2 - Fall Meeting Material Research Society of America CY - Boston, MA, USA DA - 2003-12-01 PY - 2003 AN - OPUS4-4061 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Schönhals, Andreas T1 - Molecular Dynamics and Structure of Polymers in Confining Space Revealed by Relaxation and Scattering Techniques T2 - International Workshop on Dynamics in Confinement CY - Grenoble, France DA - 2003-01-23 PY - 2003 AN - OPUS4-4108 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Schönhals, Andreas T1 - Broadband Dielectric Spetroskopy and its Application to Dynamic Glass Transition: From the Bulk to the Confined State T2 - International Discussion Seminar on Inelastic x-Ray Scattering (eingeladener Vortrag) CY - Grenoble, France DA - 2003-02-10 PY - 2003 AN - OPUS4-4109 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Schönhals, Andreas T1 - Broadband Dielectric Spetroskopy and its Application to Dynamic Glass Transition T2 - Frühjahrsschule "Festkörperphysik" der Universität Karlsruhe (eingeladene Vortrag) CY - Karlsruhe, Germany DA - 2003-02-17 PY - 2003 AN - OPUS4-4110 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Schönhals, Andreas T1 - Polar Molecules in Nanoconfinements T2 - Vortrag Universität Lyon CY - Lyon, France DA - 2003-03-31 PY - 2003 AN - OPUS4-4111 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Schönhals, Andreas T1 - Polymere in Nano-Confinements: Vergleich von Relaxationsexperimenten und (Neutronen) streuung T2 - Kolloquium der Abteilung VI CY - Berlin, Germany DA - 2003-06-05 PY - 2003 AN - OPUS4-4113 LA - deu AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Schönhals, Andreas T1 - Inverse Nanocomposites: Structure and Dynamics of Polymers Confined to Nanopores T2 - 7th International Symposium Polymers for Advanced Technologies CY - Fort Lauderdale, FL, USA DA - 2003-09-21 PY - 2003 AN - OPUS4-4191 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Schönhals, Andreas T1 - Polymers confined to nanoporous glasses: What can we leam from relaxation and scattering experiments? T2 - Softmatter Seminar des Forschungszentrums Jülich CY - Jülich, Germany DA - 2003-11-13 PY - 2003 AN - OPUS4-4192 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Schönhals, Andreas T1 - Polymers in Random Nanoporous glasses: Molecular Dynamics and Structure T2 - Fall meeting Material Researsh Society of America CY - Boston, MA, USA DA - 2003-12-01 PY - 2003 AN - OPUS4-4193 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Schönhals, Andreas T1 - Polymere in nanoporösen Gläsern: Was können wir von Relaxations- und Streuexperimenten lernen? T2 - Workshop Glasübergang CY - Berlin, Germany DA - 2003-12-14 PY - 2003 AN - OPUS4-4196 LA - deu AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Schönhals, Andreas T1 - Rotational fluctuations of water inside nanopores/nanocavities of molecular sieves T2 - Workshop Confit 2006 CY - Grenoble, France DA - 2006-03-23 PY - 2006 AN - OPUS4-12015 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Schönhals, Andreas T1 - Polymers confined to nanoporous glasses investigated by quasielastic and inelastic neutron scattering T2 - Workshop Confit 2006 CY - Grenoble, France DA - 2006-03-23 PY - 2006 AN - OPUS4-12000 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Schönhals, Andreas T1 - Molecular fluctuations of 4-n-octyl-4'cyanobiphenyl confined to nanoporous SBA-type molecular sieves with different filling degrees T2 - Workshop Confit 2006 CY - Grenoble, France DA - 2006-03-23 PY - 2006 AN - OPUS4-12005 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Schönhals, Andreas T1 - Neutron spectroscopy on polymers confined to nanoporous glasses T2 - Frühjahrstagung der Deutschen Physikalischen Gesellschaft CY - Dresden, Germany DA - 2006-03-21 PY - 2006 AN - OPUS4-12032 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Frunza, Ligia A1 - Kosslick, H. A1 - Frunza, Stefan A1 - Schönhals, Andreas T1 - Molecular dynamics of 4-n-octyl-4'-cyanobiphenyl in partially filled nanoporous SBA-type molecular sieves N2 - The molecular dynamics of 4-n-octyl-4'-cyanobiphenyl (8CB) confined to the nanopores of new SBA-type molecular sieves was investigated in a wide temperature range using broadband dielectric spectroscopy (10-2–109 Hz). One molecular sieve has a hexagonal structure of the pores while the other is a cellular nanoporous material. To explore the extent of surface interaction effects a high and a low filling degree were considered. For the molecular sieves with a high filling degree two relaxation regions were observed: a bulk-like relaxation process related to molecules, which behave as mesophase, located in the centre of the pores. The second relaxation process has a much lower relaxation rate than the former and is assigned to molecules located in a surface layer. The temperature dependence of its relaxation rates follows the Vogel–Fulcher–Tammann law, characteristic for glassy dynamics. For samples with a low filling degree only one relaxation process due to the surface layer was observed. Moreover, especially at the temperatures lower than the melting point of bulk 8CB, its relaxation rate is situated between the characteristic frequencies of the two relaxation processes observed for the pores with a high filling degree. This behaviour gives a measure of the extension of the influence of the wall on the neighbouring 8CB molecules. In addition, the differences revealed by the molecule dynamics inside the two types of nanoporous materials are related to both surface interactions and geometrical constraints. KW - Confined liquid crystals KW - Molecular sieves KW - Dielectric measurements KW - Relaxation processes KW - Glassy dynamics PY - 2006 DO - https://doi.org/10.1016/j.micromeso.2005.10.025 SN - 1387-1811 SN - 1873-3093 VL - 90 IS - 1-3 SP - 259 EP - 270 PB - Elsevier CY - Amsterdam AN - OPUS4-12118 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Schönhals, Andreas A1 - Goering, Harald A1 - Schick, C. T1 - Poly(methyl phenyl siloxane) in Random Nanoporous Glasses - Comparison of coated and uncoated confining surfaces T2 - Poly(methyl phenyl siloxane) in Random Nanoporous Glasses: Comparison of coated and uncoated confining surfaces CY - Boston, MA, USA DA - 2006-11-28 PY - 2006 VL - 899E SP - 0899-N09-05.1-0899-N09-05.6 CY - Boston AN - OPUS4-12214 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Schönhals, Andreas T1 - Structure property relationships of different polymer based nanocomposites as investigated by dieletric spectroscopy and gas transport measurements T2 - 2nd International Symposium on Nanostructured and Functional Polymer-based Materials and Nanocomposites (NANOFUN-POLY) CY - Lyon, France DA - 2006-05-29 PY - 2006 AN - OPUS4-12393 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Schönhals, Andreas T1 - Polymer based nanocomposites as investigated by dielectric spectroscopy, gas transport measurements and related techniques T2 - NoE Nanofun Polymer, 6. FP der EU CY - Poznan, Poland DA - 2006-09-01 PY - 2006 AN - OPUS4-12625 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Schönhals, Andreas T1 - Polymers confined to Nanoporous Glasses T2 - Vortrag am National Research Center, Kairo CY - Cairo, Egypt DA - 2005-10-16 PY - 2005 AN - OPUS4-11669 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Schönhals, Andreas T1 - Polymers in Random Nanoporous Glasses Investigated by Dielectric, Thermal and Neutron Spectroscopy T2 - Herbst Meeting der Amerikanischen Gesellschaft für Materialforschung, 01.12. CY - Boston, MA, USA DA - 2005-11-27 PY - 2005 AN - OPUS4-11708 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Schönhals, Andreas T1 - Molecules in nanometre confinement investigated by dieletric spectroscopy and related techniques T2 - 4. Conference of the International Dieletric Society CY - Poznan, Poland DA - 2006-09-03 PY - 2006 AN - OPUS4-13042 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Schick, C. A1 - Sukhorukov, D. A1 - Schönhals, Andreas T1 - Comparison of the Molecular Dynamics of a Liquid Crystalline Side Group Polymer Revealed from Temperature Modulated DSC and Dielectric Experiments in the Glass Transition Region N2 - Temperature modulated DSC (TMDSC) in the frequency range from 10-3 Hz to 3.4 10-2 Hz and dielectric spectroscopy in the frequency range from 10-2 Hz to 106 Hz is employed to analyze the temperature dependence of the relaxation rates of the - and of the -relaxation of a liquid crystalline polymethacrylate having a derivative of (p-alkoxy-phenyl)-benzoate as mesogenic unit in the side group. Especially the molecular assignment of the -relaxation was discussed controversial in the literature up to now. By applying a temperature derivative method it was found that the temperature dependencies of the relaxation rates of the dielectric -relaxation and of the dynamic glass transition measured by TMDSC can be described by Vogel/Fulcher/Tammann laws with the same Vogel temperature. Therefore it is argued that the dielectric -relaxation of liquid crystalline polymers is rather due to the dynamic glass transition related to the segmental dynamics of the backbone than to the transverse dipole component of the mesogenic unit. PY - 2001 DO - https://doi.org/10.1002/1521-3935(20010501)202:8<1398::AID-MACP1398>3.0.CO;2-C SN - 1022-1352 SN - 1521-3935 VL - 202 IS - 8 SP - 1398 EP - 1404 PB - Wiley-VCH Verl. CY - Weinheim AN - OPUS4-13693 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Schönhals, Andreas T1 - Polymers confined to nanoporous glasses investigated by quasielastic and inelastic neutron scattering T2 - Soft Matter User Meeting CY - Grenoble, France DA - 2006-11-22 PY - 2006 AN - OPUS4-13881 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Schönhals, Andreas T1 - Polymers in nanoconfinements investigated by various spectroscopic methods T2 - Department of Physics and Astronomy, Universität Leuven CY - Leuven, Belgium DA - 2006-11-30 PY - 2006 AN - OPUS4-14203 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Schönhals, Andreas T1 - Molecular Dynamics of polar molecules in nanometre confinement T2 - Vortrag an der Universität Lissabon, Fakultät für Chemie CY - Lisbon, Portugal DA - 2007-01-17 PY - 2007 AN - OPUS4-14503 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Schönhals, Andreas T1 - Neutron Spectroscopy on nano-confined polymers in comparison with dielectric and thermal results T2 - Jahrestagung der Deutschen Physikalischen Gesellschaft, AK Chemische Physik/Polymerphysik CY - Regensburg, Germany DA - 2007-03-26 PY - 2007 AN - OPUS4-14566 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Schönhals, Andreas A1 - Goering, Harald A1 - Schick, C. A1 - Frick, B. A1 - Mayorova, M. T1 - Segmental dynamics of poly(methyl phenyl siloxane) confined to nanoporous glasses N2 - The effect of a nanometer confinement on the molecular dynamics of poly(methyl phenyl siloxane) (PMPS) was studied by dielectric spectroscopy (DS), temperature modulated DSC (TMDSC) and neutron scattering (NS). Nanoporous glasses with pore sizes of 2.5–20 nm have been used. DS and TMDSC experiments show that for PMPS in 7.5 nm pores the molecular dynamics is faster than in the bulk which originates from an inherent length scale of the underlying molecular motions. For high temperatures the temperature dependence of the relaxation rates for confined PMPS crosses that of the bulk state. Besides finite states effects also the thermodynamic state of nano-confined PMPS is different from that of the bulk. At a pore size of 5 nm the temperature dependence of the relaxation times changes from a Vogel/Fulcher/Tammann like to an Arrhenius behavior where the activation energy depends on pore size. This is in agreement with the results obtained by NS. The increment of the specific heat capacity at the glass transition depends strongly on pore size and vanishes at a finite length scale between 3 and 5 nm which can be regarded as minimal length scale for glass transition to appear in PMPS. PY - 2007 SN - 1951-6355 SN - 1951-6401 VL - 141 IS - 1 SP - 255 EP - 259 PB - Springer CY - Berlin AN - OPUS4-14602 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Schönhals, Andreas T1 - Dielectric and neutron spectroscopy on nano-confined liquid crystals T2 - Jahrestagung der Deutschen Physikalischen Gesellschaft, AK Chemische Physik/Polymerphysik CY - Regensburg, Germany DA - 2007-03-26 PY - 2007 AN - OPUS4-14590 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Schönhals, Andreas T1 - Molecular dynamics in glass-forming liquid crystal as studied by broadband dielectric and thermal spectroscopy T2 - Jahrestagung der Deutschen Physikalischen Gesellschaft, AK Chemische Physik/Polymerphysik CY - Regensburg, Germany DA - 2007-03-26 PY - 2007 AN - OPUS4-14592 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Hao, Ning A1 - Böhning, Martin A1 - Goering, Harald A1 - Schönhals, Andreas T1 - Nanocomposites of Polyhedral Oligomeric Phenethylsilsesquioxanes and Poly(bisphenol A carbonate) as Investigated by Dielectric Spectroscopy N2 - Nanocomposites were prepared by solution blending of polyhedral oligomeric silsesquioxane with phenethyl substituents (PhenethylPOSS) into poly(bisphenol A carbonate) (PBAC). The nanocomposites were investigated by dielectric spectroscopy, differential scanning calorimetry (DSC) and density measurements. PhenethylPOSS shows one relaxation process, the α-relaxation, confirmed by DSC investigations. PBAC shows a β-relaxation at lower and an α-relaxation at higher temperatures. With increasing PhenethylPOSS content the α-relaxation of the composites shifts to lower temperatures. Thus, incorporation of PhenethylPOSS leads to a plasticization of PBAC due to a decrease of the packing density which is rationalized by density measurements. For higher concentrations of PhenethylPOSS (>10 wt %) the α-relaxation of the polycarbonate matrix splits into two peaks. Moreover, close to the α-relaxation of PhenethylPOSS a third process is observed. These results indicate a phase separation into a PBAC matrix with a few percents of molecularly solved POSS and POSS-rich domains. These POSS-rich domains are surrounded by an interfacial layer of PBAC having a higher concentration of POSS than the matrix. A phase diagram is deduced providing a miscibility criterion. For the phase separated nanocomposites an interfacial polarization phenomena is observed. Using a simplified model the time constant of this process is correlated with the size of the PhenethylPOSS-rich domains and theire increasing size with the increase of the concentration of POSS. KW - Polyhedral oligomeric silsesquioxane (POSS) KW - Polymer-based nanocomposites KW - Broadband dielectric spectroscopy KW - Interfacial polarisation PY - 2007 SN - 0024-9297 SN - 1520-5835 VL - 40 IS - 8 SP - 2955 EP - 2964 PB - American Chemical Society CY - Washington, DC AN - OPUS4-14768 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Brás, A. R. A1 - Dionísio, M. A1 - Huth, H. A1 - Schick, C. A1 - Schönhals, Andreas T1 - Origin of glassy dynamics in a liquid crystal studied by broadband dielectric and specific heat spectroscopy N2 - A combination of broadband dielectric (10-2 Hz–109 Hz) and specific heat (10-3 Hz–2×103 Hz) spectroscopy is employed to study the molecular dynamics of the glass-forming nematic liquid crystal E7 in a wide temperature range. In the region of the nematic phase the dielectric spectra show two relaxation processes which are expected theoretically: The δ relaxation which corresponds to rotational fluctuations of the molecules around its short axis and the tumbling mode at higher frequencies than the former one. For both processes the temperature dependence of the relaxation rates follows the Vogel-Fulcher-Tammann formula which is characteristic for glassy dynamics. By applying a detailed data analysis, it is shown that close to the glass transition the tumbling mode has a much steeper temperature dependence than the δ process. The former has a Vogel temperature which is by 30 K higher than that of the δ relaxation. Specific heat spectroscopy gives one relaxation process in its temperature and frequency dependence which has to be assigned to the α relaxation (dynamic glass transition). The unique and detailed comparison of the temperature dependence of the dielectric and the thermal relaxation rates delivers unambiguously that the dielectric tumbling mode has to be related to the dynamic glass transition. PY - 2007 DO - https://doi.org/10.1103/PhysRevE.75.061708 SN - 1539-3755 SN - 1063-651X VL - 75 IS - 6 SP - 061708-1-061708-8 PB - American Institute of Physics CY - Melville, NY AN - OPUS4-15041 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Schönhals, Andreas T1 - Structure property relationships of polymeric nanocomposites based on polyhedral oligomeric silsesquioxanes T2 - Meeting American Chemical Society CY - Boston, MA, USA DA - 2007-07-19 PY - 2007 AN - OPUS4-15457 LA - deu AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Hao, Ning A1 - Böhning, Martin A1 - Schönhals, Andreas T1 - Gas Transport Properties of Polymeric Nanocomposites Based on Polyhedral Oligomeric Silsesquioxanes PY - 2007 SN - 0743-0515 VL - 97 SP - 444 EP - 445 PB - Division of Polymeric Materials Science and Engineering, American Chemical Society CY - Washington, DC AN - OPUS4-15846 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Schönhals, Andreas A1 - Schick, C. A1 - Huth, H. A1 - Frick, B. A1 - Mayorova, M. A1 - Zorn, R. T1 - Molecular dynamics in glass-forming poly(phenyl methyl siloxane) as investigated by broadband thermal, dielectric and neutron spectroscopy KW - Neutron diffraction/scattering KW - Dielectric properties KW - Relaxation KW - Electric modulus KW - Glass transition PY - 2007 SN - 0022-3093 VL - 353 IS - 41-43 SP - 3853 EP - 3861 PB - North-Holland Publ. Co. CY - Amsterdam AN - OPUS4-15898 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Schönhals, Andreas T1 - Molecular mobility poly(phenyl methyl siloxane) invesstigated by thermal, dielectric and neutron spectroscopy T2 - Meeting of the American Chemical Society, PMSE CY - Boston, MA, USA DA - 2007-08-19 PY - 2007 AN - OPUS4-15463 LA - deu AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Frunza, L. A1 - Schönhals, Andreas A1 - Frunza, S. A1 - Parvulescu, V.I. A1 - Cojocaru, B. A1 - Carriazo, D. A1 - Martín, C. A1 - Rives, V. T1 - Rotational Fluctuations of Water Confined to Layered Oxide Materials - Nonmonotonous Temperature Dependence of Relaxation Times N2 - The rotational molecular dynamics of water confined to layered oxide materials with brucite structure was studied by dielectric spectroscopy in the frequency range from 10-2 to 107 Hz and in a broad temperature interval. The layered double hydroxide samples show one relaxation process, which was assigned to fluctuations of water molecules forming a layer, strongly adsorbed to the oxide surface. The temperature dependence of the relaxation rates has an unusual saddlelike shape characterized by a maximum. The model of Ryabov et al. (J. Phys. Chem. B 2001, 105, 1845) recently applied to describe the dynamics of water molecules in porous glasses is employed also for the layered materials. This model assumes two competing effects: rotational fluctuations of water molecules that take place simultaneously with defect formation, allowing the creation of free volume necessary for reorientation. The activation energy of rotational fluctuations, the energy of defect formation, a pre-exponential factor, and the defect concentration are obtained as main parameters from a fit of this model to the data. The values of these parameters were compared with those found for water confined to nanoporous molecular sieves, porous glasses, or bulk ice. Several correlations were discussed in detail, such as the lower the value of the energy of defect formation, the higher the number of defects. The pre-exponential factor increases with increasing activation energy, as an expression of the compensation law, and indicates the cooperative nature of the motional process. The involvement of the surface OH groups and of the oxygen atoms of the interlayer anions in the formation of hydrogen bonds was further discussed. For the birnessite sample, the relaxation processes are probably overlaid by a dominating conductivity contribution, which is analyzed in its frequency and temperature dependence. It is found that the conductivity of birnessite obeys the characteristics of semiconducting disordered materials. Especially the Barton/Nakajima/Namikawa relationship is fulfilled. Analyzing the temperature dependence of the direct current (dc) conductivity σ0 in detail gives some hint that σ0(T) has also an unusual saddlelike form. PY - 2007 DO - https://doi.org/10.1021/jp0717140 SN - 1089-5639 SN - 1520-5215 VL - 111 IS - 24 SP - 5166 EP - 5175 PB - Soc. CY - Washington, DC AN - OPUS4-15718 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Schönhals, Andreas A1 - Schick, C. A1 - Huth, H. A1 - Frick, B. A1 - Mayorova, M. A1 - Zorn, R. T1 - Molecular Mobility of Poly(phenyl methyl siloxane) Investigated by Thermal, Dielectric and Neutron Spectroscopy PY - 2007 SN - 0743-0515 VL - 97 SP - 948 EP - 949 PB - Division of Polymeric Materials Science and Engineering, American Chemical Society CY - Washington, DC AN - OPUS4-15736 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CHAP A1 - Schönhals, Andreas ED - Grellmann, W. ED - Seidler, S. T1 - Electrical and Dielectrical Properties KW - Polymer Testing PY - 2007 SN - 978-3-446-40900-2 IS - Kap. 6.3 SP - 335 EP - 374 PB - Carl Hanser Verlag CY - Munich AN - OPUS4-15763 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Schönhals, Andreas T1 - Dielectric properties of nanocomposites based on polyethylene and layered double hydroxide T2 - Frühjahrstagung der Deutschen Physikalischen Gesellschaft, Arbeitskreis Chemische Physik und Polymerphysik CY - Berlin, Germany DA - 2008-02-25 PY - 2008 AN - OPUS4-16700 LA - deu AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Schönhals, Andreas T1 - Dielectric and gas transport properties of polymeric nanocomposites based on polyhedral oligomeric silsesquioxanes T2 - Frühjahrstagung der Deutschen Physikalischen Gesellschaft, Arbeitskreis Chemische Physik, Polymerphysik CY - Berlin, Germany DA - 2008-02-25 PY - 2008 AN - OPUS4-16701 LA - deu AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Schönhals, Andreas T1 - Dynamics of n-alkyl-cyanobiphenyl and cyano-n-alkylbenzoate molecules in a surface layer adsorbed onto aerosil T2 - Frühjahrstagung der Deutschen Physikalischen Gesellschaft, Arbeitskreis Chemische Physik, Polymerphysik CY - Berlin, Germany DA - 2008-02-25 PY - 2008 AN - OPUS4-16698 LA - deu AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Ramanujam, Maalolan A1 - Wachtendorf, Volker A1 - Mix, Renate A1 - Schönhals, Andreas A1 - Friedrich, Jörg Florian ED - Reichert, T. T1 - Influence of UV weathering and humidity on surface & bulk properties of LDPE N2 - The outdoor weathering of polymers is mainly due to UV radiation, water, Pollution, humidity, temperature etc. To understand the effects of weathering, simulated tests need to be undertaken in lab scale. Such tests must be quite efficient and similar to the effects of natural weathering. This paper mainly focuses on the effects of UV radiation along with humidity on LDPE. T2 - 5th European weathering symposium - Natural and artificial ageing of polymers CY - Lisbon, Portugal DA - 21.09.2011 KW - LDPE KW - UV weathering KW - Humidity PY - 2011 SN - 978-3-9813136-2-8 N1 - Serientitel: CEEES Publication – Series title: CEEES Publication IS - 15 SP - 211 EP - 218 PB - GUS (Gesellschaft für Umweltsimulation) CY - Pfinztal AN - OPUS4-24536 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Schönhals, Andreas T1 - Dielectric Spectroscopy - Basics, Effects and Examples - T2 - Graduiertenkolleg "Analyse und Simulation elektrischer Wechselwirkungen zwischen Implantaten und Biosystemen", Universität Rostock CY - Rostock, Germany DA - 2011-10-20 PY - 2011 AN - OPUS4-24638 LA - deu 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 - Kolloquiumsvortrag am National Research Center Canada - Industrial Materials CY - Boucherville, Canada DA - 2011-09-30 PY - 2011 AN - OPUS4-24639 LA - deu AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Schönhals, Andreas T1 - Molecular Dynamics in Nanometre Confinement T2 - Broadband Dielectric Spectroscopy and its Advanced Technological Applications CY - Perpignan, France DA - 2011-09-21 PY - 2011 AN - OPUS4-24640 LA - deu AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER -