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 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 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 -