(336j) Reverse Selective Gas Transport in PTMSP Membranes: Nanoscale Analysis

Poly(1-trimethylsilyl-1-propyne) (PTMSP), a member of the polyacytelene family, is known to exhibit the highest gas permeability among all the synthetic polymeric systems as well as very high organic vapor/permanent-gas selectivity. It was found that addition of nanoparticles to PTMSP membranes further enhances the gas permeabilities. However the bulk permeability measurements render limited insight into factors causing the apparent enhancements in the transport properties. Our group has demonstrated the measurement of in-situ gas fluxes on a nanoscale by means of Flux Lateral Force Microscopy (F-LFM). This technique, which is based on atomic force microscopy (AFM), utilizes the lubricating effect and the mechanical property changes in the membrane to determine local fluxes. In this paper we present the nanoscale gas transport analysis in thin PTMSP membranes by F-LFM and these local fluxes are compared to the global bulk measurements. The sensitivity of F-LFM technique is demonstrated by presenting the reverse selective transport rates of He and CO2 in PTMSP membranes as detected by the technique. The paper will also address the impact of aging, and flux dependence on film thickness.