Stabilization of gas transport properties of PTMSP with porous aromatic framework: Effect of annealing

This work was focused on the study of physical aging of PTSMP and preventing this effect via incorporation of porous aromatic frameworks (PAF-11). The dense PTMSP membranes with PAF-11 content of 0, 1, 5 and 10 wt% were stepwise annealed in air at 100 °C for up to 510 h with constant monitoring of O2, N2 and CO2 permeability (measured at 30 °C). As-cast and aged PTMSP samples were characterized by means of helium pycnometry, dynamic mechanical analysis and IR spectroscopy. Gas transport characteristics of the PTMSP sample containing 10 wt% of PAF-11 became stable upon annealing at 100°С within the short time interval (100-200 h). However, for all other samples containing 5 wt% of PAF-11 or less, gas permeability gradually decreased with time. According to the IR analysis, upon high-temperature treatment, PAF-11 nanoparticles tended to migrate from the sub-layer region into the membrane matrix bulk. According to the helium pycnometry, the introduction of PAF-11 to the PTMSP matrix provided a loosened packaging of polymer chains, and the structure became more stabilized since the porous filler served as a “physical” cross-linker.