CH4 selective membranes CH4 solubility CO2 separation LTA) POSS® PVA Poly(trimethylsilyl-1-propyne) (PTMSP) RHO borane characterization techniques compatibility filler dispersion flat-sheet membrane gas separation gas separation membrane hollow fiber membrane hydrolytic bulk degradation mechanism in vitro human neural models ion exchange capacity membrane fabrication membrane modification mixed matrix membranes modeling nanocomposite membranes nanoporous polybenzimidazole membranes neural tissue regeneration photo-assisted polymerization poly (?-caprolactone) polymer of intrinsic microporosity porous nanoparticles