Novel PTMSP-based membranes containing elastomeric fillers: Enhanced 1-butanol/water pervaporation selectivity and permeability

To improve organic solvent preferential permeation of poly[1-(trimethylsilyl)-1-propyne] (PTMSP) and to provide efficient separation of dilute 1-butanol/water mixtures, the membranes were modified by the addition of minor amounts of a soft elastomeric filler, poly(dimethylsilmethylene) (PDMSM), to the host polymeric matrix. As compared with virgin PTMSP membranes, the modified membranes demonstrate better 1-butanol/water pervaporation selectivity and permeability. This unique coupled phenomenon is observed at low concentrations of the elastomeric filler (~1–3 wt%) in the host matrix and for the feed aqueous mixtures containing 0.6–3.6 wt% of butanol. For vacuum pervaporation of butanol solutions, introduction of only 1.2 wt% of PDMSM into the PTMSP matrix makes it possible to increase the permeate flux up to 75% and the separation factor up to 67%. When studying pervaporation of the feed solution containing 2 wt% of butanol, the dependences of the permeate flux and separation factor on the elastomeric filler content in the host matrix show the well-pronounced maxima at 1.2–3 wt% (MW of the elastomer is 83–1000 kg/mol). In this case, the attained permeate flux is 1.5–1.8 times higher than that of the virgin PTMSP, and the separation factor increases by a factor of 1.4–1.7. The corresponding values of thickness-corrected flux and separation factor for the PTMSP/PDMSM membranes are 3.5–4.0 kg m/(m 2 h) and 112–136, respectively. More specifically, the 30 µm thick PTMSP/PDMSM (98/2) membrane exhibited permeate flux 0.12 kg/(m 2 h) and separation factor 128 upon pervaporation of 2 wt% aqueous butanol solution at 25 °C. The experiments on the equilibrium sorption of butanol solutions on the PTMSP membranes modified by the elastomeric filler revealed similar dependences with their well-pronounced maxima in the same region of the PDMSM content. The highest value of membrane selectivity α mem for PTMSP/PDMSM is 8.9 as compared with 5.3 for the virgin PTMSP membranes. Qualitative explanation of the enhanced pervaporation selectivity coupled with the improved permeate flux for the PTMSP/PDMSM membranes was advanced.