Effect of fumed silica nanoparticles on the gas permeation properties of substituted polyacetylene membranes

The gas permeability of three substituted polyacetylenes, poly(1-chloro-2-phenylacetylene) (PClPA), poly[1-phenyl-2-(4-trimethylsilyl) phenylacetylene] (PTMSDPA), and poly[1-(trimethylsilyl)-1-propyne] (PTMSP), increased systematically with increasing content of nonporous fumed silica (FS) nanoparticles. For instance, the oxygen permeability coefficient (PO ₂) of PClPA containing 30 wt∈% FS was 86 barrers, which was 10 times higher than that of the unfilled polymer (PO₂=8.6 barrers). The extent of permeability increase with the addition of FS was smaller when the permeability of the original polymer was higher. The order of the permeability increase in FS-filled polymers was as follows: PClPA > PTMSDPA > PTMSP. The addition of FS resulted in the decrease of O₂/N₂ permselectivity of these polymers. The H₂/CH₄ permselectivity largely decreased with increasing FS content in PClPA, while it hardly changed with FS loading in PTMSP. The gas solubility of PClPA was practically independent of FS content, and the increase in gas permeability in filled PClPA resulted from an increase in diffusivity with the addition of FS.