Copolymerization modification of poly(vinyltriethoxysilane) membranes for ethanol recovery by pervaporation

In this study, a copolymerization modification method is used to modify the rigid structure of a high-flux poly(vinyltriethoxysilane) (PVTES) membrane, which was prepared from VTES monomers in our previous work, to further enhance its separation factor. A value of R/Si, which could characterize the density of organic groups and the chain flexibility in membrane materials, is introduced here to guide the selection of modification chemicals. Modifiers with different polymerization degree but the same flexible chain unit (DMDES, HSO and PDMS) are chosen to be copolymerized with PVTES. Analysis results show that the PVTES-HSO membrane possesses lower thickness, higher amount of hydrophobic groups, and an inner structure with greater chain flexibility and lower crystallinity, leading to the best pervaporation (PV) performance among these modified membranes, which is much better than the original PVTES membrane. Furthermore, PVTES-HSO membranes with different R/Si values are prepared to optimize their PV performance. And the optimal PVTES-HSO membrane (R/Si = 1.4) shows the best performance with the separation factor of 6.6 and flux up to 8160 g m−2 h−1 when separating 9 wt% ethanol aqueous solution at 35 °C.