TY - JOUR A1 - Dümichen, Erik A1 - Braun, Ulrike A1 - Sturm, Heinz A1 - Kraemer, R. A1 - Deglmann, P. A1 - Gaan, S. A1 - Senz, R. T1 - A new molecular understanding of the thermal degradation of PA 66 doped with metal oxides: Experiment and computation JF - Polymer degradation and stability N2 - The thermal molecular degradation of polyamide 66 (PA 66) doped with (partially supported) metal oxide particles (Fe2O3, ZnO, Al2O3) was investigated qualitatively and quantitatively using common analysis techniques like thermogravimetry coupled with IR-spectroscopic evolved gas analysis (TGA-FTIR). Using pyrolysis coupled with gas chromatography mass spectrometry (Py-GC-MS), qualitative conclusions were drawn about the complex hydrocarbon products. However, the combination of TGA with solid-phase extraction, followed by thermal desorption gas chromatography mass spectrometry (TED-GC-MS), allows qualitative and even semi-quantitative conclusions about the decomposition pathway of PA 66 in the presence of various metal oxide particles. The investigations under inert conditions showed that the presence of metal particles increases the rate of decarboxylation and deamination reactions, as well as the formation rate of cyclopentanone and pyridine derivatives. These species are a consequence of various condensation reactions. The condensation reactions release a large amount of water, thus triggering the hydrolysis of PA 66. Molecular thermal degradation mechanisms were developed for the main decomposition as well as for the condensation reactions and supported by quantum chemical calculations. The catalytic effect of the metal oxides in PA 66 increases in the following order: PA 66 = PA 66 – Al2O3 < PA 66 – Fe2O3 < PA 66 – ZnO. KW - PA 66 KW - Metal oxide particles KW - Thermal degradation KW - Solid-phase extraction KW - Molecular modeling PY - 2015 DO - https://doi.org/10.1016/j.polymdegradstab.2015.07.011 SN - 0141-3910 SN - 1873-2321 VL - 120 SP - 340 EP - 356 PB - Elsevier Ltd. CY - London AN - OPUS4-33806 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Heuchel, M. A1 - Böhning, Martin A1 - Hölck, Ole A1 - Siegert, M.R. A1 - Hofmann, D. T1 - Atomistic Packing Models for Experimentally Investigated Swelling States Induced by CO2 in Glassy Polysulfone and Poly(ether sulfone) JF - Journal of polymer science B, polymer physics N2 - Atomistic packing models have been created, which help to better understand the experimentally observed swelling behavior of glassy polysulfone and poly (ether sulfone), under CO2 gas pressures up to 50 bar at 308 K. The experimental characterization includes the measurement of the time-dependent volume dilation of the polymer samples after a pressure step and the determination of the corresponding gas concentrations by gravimetric gas-sorption measurements. The models obtained by force-field-based molecular mechanics and molecular dynamics methods allow a detailed atomistic analysis of representative swelling states of polymer/gas systems, with respect to the dilation of the matrix. Also, changes of free volume distribution and backbone mobility are accessible. The behavior of gas molecules in unswollen and swollen polymer matrices is characterized in terms of sorption, diffusion, and plasticization. KW - Molecular modeling KW - Volume dilation KW - Gas sorption KW - Poly(ether sulfones) KW - Free volume KW - Swelling KW - Molecular dynamics KW - Diffusion KW - Plasticization PY - 2006 DO - https://doi.org/10.1002/polb.20844 SN - 0887-6266 SN - 1099-0488 VL - 44 IS - 13 SP - 1874 EP - 1897 PB - Wiley CY - Hoboken, NJ AN - OPUS4-12398 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Hölck, Ole A1 - Böhning, Martin A1 - Heuchel, M. A1 - Siegert, M.R. A1 - Hofmann, D. T1 - Gas sorption isotherms in swelling glassy polymers - detailed atomistic simulations JF - Journal of membrane science N2 - Detailed atomistic simulations were carried out for swelling polymer/gas systems related to experimental sorption and dilation data for CO2 and CH4 in three glassy polymers (polysulfone PSU, the polyimide 6FDA-TrMPD, and a polymer of intrinsic microporosity PIM-1) at 308 K (35 °C) and pressures up to 50 bar. Corresponding experiments were performed with a gravimetric sorption balance and a dilatometer based on a capacitance distance sensor. For each polymer/gas system molecular packing models were prepared and equilibrated for two reference states: the pure polymer is taken as reference for the respective 'unswollen' state and similarly the state of the highest penetrant pressure reached in the corresponding experiment is taken to represent the 'swollen' state. Models for the latter were constructed in agreement with experimental data (pressure, temperature, gas concentration and volume dilation). Concentration–pressure isotherms of each polymer/gas system were obtained using Grand Canonical Monte Carlo (GCMC) simulations for both reference states (depleted of gas molecules), which are in good agreement with the experimental data in the respective pressure range. As expected these isotherms – due to the simulation technique used, merely based on hole-filling in a static host matrix – do not represent the sorption behavior over a broader range of gas pressures which may involve significant structural rearrangements as well as swelling and relaxational phenomena. Nevertheless, a linear combination of the two GCMC-isotherms allows the interpolation in order to describe the nonlinear gas sorption in the glassy polymers under investigation covering the penetrant pressure range between the reference states in good agreement with the experimental results. KW - Gas sorption KW - Dilation KW - Molecular modeling KW - Polysulfone KW - Polyimide KW - Polymer of intrinsic microporosity (PIM-1) PY - 2013 DO - https://doi.org/10.1016/j.memsci.2012.10.023 SN - 0376-7388 SN - 1873-3123 VL - 428 SP - 523 EP - 532 PB - Elsevier B.V. CY - Amsterdam AN - OPUS4-27599 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Hölck, Ole A1 - Heuchel, M. A1 - Böhning, Martin A1 - Hofmann, D. T1 - Simulation of Experimentally Observed Dilation Phenomena During Integral Gas Sorption in Glassy Polymers JF - Journal of polymer science B, polymer physics N2 - A molecular modeling investigation of dilation effects induced by sorbed gas molecules in two glassy polymers is presented. As experimental reference, integral sorption of CO2 and CH4 was measured for polysulfone (PSU) and a polyimide (6FDA-TrMPD, PI4) at 308 K and a pressure of 10 bar. Simultaneously, the gas induced swelling effect was measured with a dilatometer based on a capacitive distance sensor recorded. The experimental evidence of the (on the observed time scale and concentration levels) elastic nature of the gas induced dilation is supported by the dilation and contraction behavior observed in molecular dynamics (MD) simulations of respective detailed atomistic packing models. These models were constructed in accordance with gas concentration levels obtained from the experimental sorption results. Quantitative deviations between simulated and measured dilations are discussed as a consequence of an anelastic response of the polymer matrix which is too fast to be resolved in the experiments whose kinetics is dominated by diffusional processes. In the simulation, the initial insertion of penetrant molecules into equilibrated packing models circumvents the slow diffusional process of the experiment and allows a reasonable representation of the dilation process as well as a closer investigation. Our simulation approach reveals a different behavior for PSU and PI4 on the corresponding time scale. Most likely, the different chain mobility of the two polymers is responsible for the respective response to the inserted amount of gas molecules which is discussed in terms of the different chain mobilities of the two polymers. KW - Diffusion KW - Dilation KW - Gas sorption KW - Molecular modeling KW - Poly(ether sulfones) KW - Polyimides KW - Swelling PY - 2008 DO - https://doi.org/10.1002/polb.21342 SN - 0887-6266 SN - 1099-0488 VL - 46 IS - 1 SP - 59 EP - 71 PB - Wiley CY - Hoboken, NJ AN - OPUS4-16206 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Kolb, U. A1 - Büscher, K. A1 - Helm, C.A. A1 - Lindner, A. A1 - Thünemann, Andreas A1 - Menzel, Michael A1 - Higuchi, M. A1 - Kurth, D.G. T1 - The solid-state architecture of a metallosupramolecular polyelectrolyte JF - Proceedings of the national academy of sciences of the United States of America N2 - Self-assembly of Fe(II) and the ditopic ligand 1,4-bis(2,2':6',2"-terpyridine-4'-yl)benzene results in equilibrium structures in solutions, so-called metallosupramolecular coordination polyelectrolytes (MEPEs). It is exceedingly difficult to characterize such macromolecular assemblies, because of the dynamic nature. Therefore, hardly any structural information is available for this type of material. Here, we show that from dilute solutions, where small aggregates predominate, it is possible to grow nanoscopic crystals at an interface. A near atomic resolution structure of MEPE is obtained by investigating the nanoscopic crystals with electron diffraction in combination with molecular modeling. The analysis reveals a primitive monoclinic unit cell (P21/c space group, a = 10.4 Å, b = 10.7 Å, c = 34.0 Å, α = γ = 90°, β = 95°, ρ = 1.26 g/cm³, and Z = 4). The MEPE forms linear rods, which are organized into sheets. Four sheets intersect the unit cell, while adjacent sheets are rotated by 90° with respect to each other. The pseudooctahedral coordination geometry of the Fe(II) centers is confirmed by Mössbauer spectroscopy. The combination of diffraction and molecular modeling presented here may be of general utility to address problems in structural materials science. KW - Polymer KW - Polyelectrolyte KW - Electron diffraction KW - Mössbauer spectroscopy KW - Molecular modeling KW - Supramolecular chemistry PY - 2006 SN - 0027-8424 SN - 1091-6490 VL - 103 IS - 27 SP - 10202 EP - 10206 PB - National Academy of Sciences CY - Washington, DC AN - OPUS4-12495 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER -