Pervaporation properties of surface-modified poly[(1-trimethylsilyl-1-propyne] membranes

Poly[1-(trimethylsilyl)-1-propyne] (PTMSP) membranes were surface-modified using polymer additives and their pervaporation properties for an aqueous ethanol solution were investigated. The polymer additives, PFA-g-PDMS and PMMA-g-PDMS, were synthesized by graft-co-polymerization of fluoroacrylate (PFA) and oligo dimethylsiloxane (DMS), and methylmethacrylate (MMA), respectively. The contact angle of water on the surface of the air-side of the surface-modified PTMSP membranes increased by the addition of PFA-g-PDMS and PMMA-g-PDMS. These results suggest that the surface-modified PTMSP membranes were more hydrophobic. Also, X-ray photoelectron spectroscopy (XPS) measurements supported that the polymer additives were concentrated at the surface of the air-side of the modified PTMSP membranes. The ethanol/water selectivity of the PTMSP membrane modified with PFA-g-PDMS increased significantly without a large decrease in flux compared with that of the PTMSP membrane. On the other hand, after modification of PTMSP with PMMA-g-PDMS both the flux and ethanol/water selectivity had a maximum at a certain amount Of PMMA-g-PDMS. The ethanol/water selectivity of the modified membrane was higher than that of the PTMSP membrane. High ethanol/water selectivity of the surface-modified PTMSP membranes depended on the solubility selectivity of the permeating species.