Silica filled poly(1-trimethylsilyl-1-propyne) nanocomposite membranes: Relation between the transport of gases and structural characteristics

The performance of poly(1-trimethylsilyl-1-propyne) (PTMSP)/silica nanocomposites was studied for membranes with a filler content between 0 and 50 wt%. An increase in permeability and a decrease in vapor selectivity was measured with increasing filler content. The free volume sizes and interstitial mesopore sizes of the composites were determined by use of positron annihilation lifetime spectroscopy (PALS). In addition to an increase in large free volume size with increasing filler content, interstitial mesopores were observed in all PTMSP/silica nanocomposites. The size of these interstitial cavities, located between the particles of a silica agglomerate, was increasing with increasing filler concentration. The presence of these agglomerates was visualized by TEM. The existence of the cavities was confirmed by nitrogen adsorption measurements. The hydrogen, nitrogen and propane permeability was clearly correlated with the size of the interstitial mesopores.