TY - JOUR A1 - Zorn, R. A1 - Szymoniak, Paulina A1 - Kolmangadi, Mohamed Aejaz A1 - Malpass-Evans, R. A1 - McKeown, N. A1 - Tyagi, M. A1 - Böhning, Martin A1 - Schönhals, Andreas T1 - Low frequency vibrations and diffusion in disordered polymers bearing an intrinsic microporosity as revealed by neutron scattering N2 - The microscopic diffusion and the low frequency density of states (VDOS) of PIM-EATB(CH3) are investigated by inelastic and quasi-elastic neutron scattering where also the demethylated counterpart of PIM-EA-TB(H2) is considered. These intrinsic microporous polymers are characterized by large BET surface area values of several hundred m2/g and pore sizes between 0.5 and 2 nm. Detailed comparison is made to the archetype of polymers of intrinsic microporosity, PIM-1, and polynorbornenes also bearing a microporosity. Due to the wavelength of neutrons, the diffusion and vibrations can be addressed on microscopic length and time scales. From the inelastic neutron scattering experiments the low frequency density of states (VDOS) is estimated which shows excess contributions to the Debye-type VDOS known as Boson peak. It was found that the maximum frequency of the Boson peak decreases with increasing microporosity characterized by the BET surface area. However, besides the BET surface area, additional factors such as the backbone stiffness govern the maximum frequency of the Boson peak. Further the mean squared displacement related to microscopic motions was estimated from elastic fixed window scans. At temperatures above 175 K, the mean squared displacement PIM-EA-TB(CH3) is higher than that for the demethylated counterpart PIM-EA-TB(H2). The additional contribution found for PIM-EATB(CH3) is ascribed to the rotation of the methyl group in this polymer because the only difference between the two structures is that PIM-EA-TB(CH3) has methyl groups where PIM-EA-TB(H2) has none. A detailed comparison of the molecular dynamics is also made to that of PIM-1 and the microporous polynorbornene PTCNSi1. The manuscript focuses on the importance of vibrations and the localized molecular mobility characterized by the microscopic diffusion on the gas Transport in polymeric separation membranes. In the frame of the random gate model localized fluctuations can open or close bottlenecks between pores to enable the diffusion of gas molecules. KW - Polymer of intrisic microporosity KW - Neutron scattering KW - Boson peak KW - Methyl group rotation PY - 2021 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:b43-538490 VL - 11 IS - 12 SP - 1 EP - 16 PB - MDPI CY - Basel AN - OPUS4-53849 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Cano Murillo, Natalia A1 - Szymoniak, Paulina A1 - Smales, Glen Jacob A1 - Sturm, Heinz A1 - Schönhals, Andreas T1 - Electrospun nanocomposites fibers of polycarbonate and taurine modified boehmite nanoparticles - What can be learned from structural and thermal investigations N2 - Though the reinforcing properties of inorganic particles in thermosetting nanocomposites, has been exploited, the integration of nanoparticles continues to be challenging in terms of their homogeneous distribution and their manipulation which can contribute to occupational hazards. Due to a second encapsulations of nanoparticles, electrospun nanocomposite fibers containing nanoparticles might be an alternative for overcoming these issues, as the fiber nonwovens contains the nanoparticles allowing for safer manipulation. Here, the morphology, and the thermal properties of electrospun polycarbonate fibers containing taurine modified boehmite nanoparticles (BNP) are investigated by means of small and wide-angle X-ray scattering as well as fast scanning and temperature modulated fast scanning calorimetry for the first time. The latter techniques allow the investigation of the thermal properties of single fibers at heating rates up to 10^4 K s^-1 keeping its structure intact. A quantitative analysis of the scattering data reveals a porous structure of the fibers. The porous structure is quantified regarding the pore volume and the pore size. A constant amount of aggregation is found even for the highly BNP loaded fibers. Thermal analysis on the fibers reveals a rigid amorphous fraction (RAF) where it is known that RAF determinates the properties of a nanocomposite to a large extent. For the fibers RAF amounts up to 40 wt%, which is essential higher compared to equally formulated PC/BNP composite cast films. The RAF in the case of the fibers, is not only due to the presence of particles in the polymer but also due to orientation effects induced by the electrospinning process. KW - Nanocomposite fibers KW - Electrospinning KW - X-ray scattering KW - Fast scanning calorimetry KW - Rigid amorphous fraction PY - 2021 U6 - https://doi.org/10.1021/acsapm.1c01265 VL - 3 IS - 12 SP - 6572 EP - 6585 PB - ACS AN - OPUS4-53871 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Gawek, Marcel A1 - Madkour, Sherif A1 - Szymoniak, Paulina A1 - Radnik, Jörg A1 - Schönhals, Andreas T1 - Energy Dependent XPS Measurements on Thin Films of a Poly(vinyl methyl ether)/Polystyrene Blend in Dependence on Film Thickness – Concentration Profile on a Nanometer Resolution to Understand the Behavior of Nanofilms N2 - The composition of the surface layer in dependence from the distance of the polymer/air interface in thin films with thicknesses below 100 nm of miscible polymer blends in a spatial region of a few nanometers is not investigated completely. Here, thin films of the blend poly vinyl methyl ether) (PVME)/polystyrene (PS) with a composition of 25/75 wt% are investigated by Energy Resolved X-ray Photoelectron Spectroscopy (ER-XPS) at a synchrotron storage ring using excitation energies lower than 1 keV. By changing the energy of the photons the information depth is varied in the range from ca. 1 nm to 10 nm. Therefore, the PVME concentration could be estimated in dependence from the distance of the polymer/air interface for film thicknesses below 100 nm. Firstly, as expected for increasing information depth the PVME concentration decreases. Secondly, it was found that the PVME concentration at the surface has a complicated dependence on the film thickness. It increases with decreasing film thickness until 30 nm where a maximum is reached. For smaller film thicknesses the PVME concentration decreases. A simplified layer model is used to calculate the effective PVME concentration in the different spatial regions of the surface layer. KW - Energy dependent XPS KW - Soft X-ray KW - Thin films PY - 2021 U6 - https://doi.org/10.1039/d1sm00656h VL - 17 IS - 29 SP - 6985 EP - 6994 PB - The Royal Chemical Society AN - OPUS4-53039 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Schönhals, Andreas A1 - Szymoniak, Paulina A1 - Kolmangadi, Mohamed Aejaz A1 - Böhning, Martin A1 - Zamponi, M. A1 - Frick, B. A1 - Appel, M. A1 - Günther, G. A1 - Russina, M. A1 - Alentiev, D. A1 - Bermeshev, M. A1 - Zorn, R. T1 - Microscopic dynamics of highly permeable super glassy polynorbornenes revealed by quasielastic neutron scattering N2 - The molecular dynamics of addition-type poly(tricyclononenes) with Si-substituted bulky side groups has been investigated by a combination of neutron time-of-flight and neutron backscattering spectroscopy methods on a time scale from 0.1 ps to ca. 3 ns. The investigated poly(tricyclononenes) PTCNSi1 and PTCNSi2g both bear a high microporosity which makes them promising candidates for active separation layers for gas separation membranes. At least for larger gas molecules it is assumed that the pathways for diffusion require an enlargement of pre-existing micropores in terms of an activated zone. A low temperature relaxation process was found for both polymers by the performed neutron scattering experiments. 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. For PTCNSi1 (3 methyl groups in the monomeric unit) it was found that all methyl groups take part in the methyl group rotation whereas for PTCNSi2g (6 methyl groups in monomeric unit) a considerable number of methyl groups are blocked in their rotation. This immobilization of methyl groups is due to the sterically demanding arrangement of the methyl groups in PTCNSi2g. This conclusion is further supported by the result that the activation energy for the methyl group rotation is three times higher for PTCNSi2g than that of PTCNSi1. KW - Highly permeably polynorbornenes KW - Polymers of intrinsic microporosity KW - Gas separation membranes KW - Quasielastic neutron scattering PY - 2021 U6 - https://doi.org/10.1016/j.memsci.2021.119972 SN - 0376-7388 VL - 642 PB - Elesevier B.V. AN - OPUS4-53508 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Omar, Hassan A1 - Smales, Glen Jacob A1 - Henning, S. A1 - Li, Z. A1 - Wang, D.-Y. A1 - Schönhals, Andreas A1 - Szymoniak, Paulina T1 - Calorimetric and Dielectric Investigations of Epoxy-Based Nanocomposites with Halloysite Nanotubes as Nanofillers N2 - Epoxy nanocomposites are promising materials for industrial applications (i.e., aerospace, marine and automotive industry) due to their extraordinary mechanical and thermal properties. Here, the effect of hollow halloysite nanotubes (HNT) on an epoxy matrix (Ep) was the focus of the study. The structure and molecular mobility of the nanocomposites were investigated using a combination of X-ray scattering, calorimetry (differential (DSC) and fast scanning calorimetry (FSC)) and dielectric spectroscopy. Additionally, the effect of surface modification of HNT (polydopamine (PDA) and Fe(OH)3 nanodots) was considered. For Ep/HNT, the glass transition temperature (Tg) is was de-creased due to a nanoparticle-related decrease of the crosslinking density. For the modified system, Ep/m-HNT, the surface modification resulted in enhanced filler–matrix interactions leading to higher Tg values than the pure epoxy in some cases. For Ep/m-HNT, the amount of interface formed between the nanoparticles and the matrix ranged from 5% to 15%. Through BDS measurements, localized fluctuations were detected as a β- and γ-relaxation, related to rotational fluctuations of phenyl rings and local reorientations of unreacted components. A combination of calorimetry and BDS dielectric spectroscopy revealed a dynamic and structural heterogeneity of the matrix, as confirmed by two glassy dynamics in both systems, related to regions with different crosslinking densities. KW - Rigid amorphous fraction KW - Epoxy nanocomposites KW - Halloysite nanotubes KW - X-ray scattering KW - Differential scanning calorimetry KW - Broadband dielectric spectroscopy KW - Flash DSC PY - 2021 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:b43-526668 VL - 13 IS - 10 SP - 1634 PB - MDPI AN - OPUS4-52666 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Szymoniak, Paulina A1 - Omar, Hassan A1 - Schönhals, Andreas T1 - Spatial Inhomogeneity, Interfaces and Complex Vitrification Behavior of Epoxy-based Materials N2 - This work deals with an in-depth comparative investigation of the structure, molecular mobility and vitrification kinetics of three bisphenol A diglycidyl ether (DGEBA)-based materials with different nanofillers: taurine-modified layered double hydroxide (T-LDH) and halloysite nanotubes (HNTs). The chosen methodology comprises I) small – and wide – angle X-ray scattering (SAXS/WAXS) II) calorimetry in the forms of a) conventional DSC and b) static fast scanning calorimetry (FSC), III) broadband dielectric spectroscopy (BDS), as well as IV) specific heat spectroscopy in the forms of a) temperature modulated DSC, and b) temperature modulated FSC. T2 - Abteilungsseminar 6. - FB 6.6 CY - Online meeting DA - 06.05.2021 KW - Broadband dielectric spectroscopy KW - Epoxy nanocomposites KW - Halloysite nanotubes KW - X-ray scattering KW - Differential scanning calorimetry KW - Rigid amorphous fraction KW - Flash DSC PY - 2021 AN - OPUS4-52697 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CHAP A1 - Szymoniak, Paulina A1 - Qu, Xintong A1 - Schönhals, Andreas A1 - Sturm, Heinz ED - Sinapius, M. ED - Ziegmann, G. T1 - Characterization of Polymer Nanocomposites N2 - The complex effect of nanoparticles on an epoxy-based and anhydride cured DGEBA/Boehmite nanocomposite with different particle concentrations is considered in this chapter. A combination of X-ray scattering, calorimetry (fast scanning and temperature modulated calorimetry) and dielectric spectroscopy was employed to characterize the structure, vitrification kinetics and the molecular dynamics of the nanocomposites. Firstly, the unfilled polymer was found to be intrinsically heterogeneous, showing regions with different crosslinking density, indicated by two separate dynamic glass transitions. Moreover, the glass transition temperature decreases with increasing nanoparticle concentration, as a result of changes in the crosslinking density. In addition, it was shown that the incorporation of nanoparticles can result in simultaneous increase in the number of mobile segments for low nanoparticle concentrations and on the other hand, for higher loading degrees the number of mobile segments decreases, due to the formation of an immobilized interphase. KW - Rigid amorphous fraction KW - Epoxy nanocomposites KW - X-ray scattering KW - Differential scanning calorimetry KW - Broadband dielectric spectroscopy KW - Flash DSC PY - 2021 U6 - https://doi.org/10.1007/978-3-030-68523-2_4 SP - 55 EP - 77 PB - Springer Nature AN - OPUS4-52698 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Szymoniak, Paulina A1 - Omar, Hassan A1 - Schönhals, Andreas A1 - Qu, Xintong T1 - Spatial Inhomogeneity, Interfaces and Complex Vitrification Behavior of Epoxy-based Materials by Broadband Dielectric Spectroscopy and Calorimetry N2 - Although in the last decades epoxy-based nanocomposites have been successfully adopted by the marine, automotive and aerospace industries they are still rarely studied on a fundamental level. This work deals with an in-depth comparative investigation of the structure, molecular mobility and vitrification kinetics of three bisphenol A diglycidyl ether (DGEBA)-based materials with different nanofillers: I) taurine-modified layered double hydroxide (T-LDH), II) boehmite (BNPs) and III) halloysite nanotubes (HNTs). Moreover, the effect of different hardeners (diethylene triamine and methyl tetrahydrophtalic acid anhydride) on the unfilled epoxy matrix is addressed as well. The chosen methodology comprises I) small – and wide – angle X-ray scattering (SAXS/WAXS) II) calorimetry in the forms of a) conventional DSC and b) static fast scanning calorimetry (FSC), III) broadband dielectric spectroscopy (BDS), as well as IV) specific heat spectroscopy in the forms of a) temperature modulated DSC, and b) temperature modulated FSC. The combination of these techniques proved an intrinsic spatial heterogeneity of epoxy-based materials, evidenced by two separate segmental relaxation processes. Although, depending on the hardener the response of the systems to calorimetric and dielectric investigations was different, in a broader sense similar conclusions can be extracted on the structural heterogeneity. As expected from the two distinct α-processes, it was shown that, in parallel to the main glass transition, epoxy-based materials can exhibit an additional low temperature vitrification mechanism, which was not discussed in prior studies for an unfilled network former. Furthermore, the interfacial region (so-called rigid amorphous fraction) was qualitatively and quantitatively addressed, in dependence of the employed nanofiller structure. T2 - Webinar University of Southern Denmark CY - Online meeting DA - 20.01.2021 KW - BDS KW - Nanocomposites KW - Epoxy KW - Rigid amorphous fraction KW - TMDSC KW - Flash DSC PY - 2021 AN - OPUS4-52036 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 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:b43-523199 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 -