Photopolymerized Fabrication Method for PDMS Pervaporative Membranes

The polydimethylsiloxane (PDMS) membrane can be considered the benchmark of alcohol-selective membranes, and its preparation method by photopolymerization shows a great potential on the industrial scale. However, a single photopolymerization system by a free radical or cation is still a challenge to simultaneously have a high reaction speed and oxygen insensitivity. In this work, we proposed a free radical/cationic hybrid membrane-forming system toward PDMS. Both methacrylate groups and epoxy groups were introduced into the PDMS chain by the covalent bonding of 3-methacryloxypropylmethyldimethoxysilane and 3-glycidyloxypropyl(dimethoxy)methylsilane with PDMS. This hybrid system can be quickly cured by a free radical reaction which weakens the oxygen inhibition by a cationic reaction. Furthermore, the transport structure of membranes is effectively controlled by the difference in the reactivity between methacrylate and epoxy groups, where the formed molecular weight and viscosity of the prepolymer are changed from 62,860 to 108,198 g mol–1 and 1.53 to 2.26 Pa s, respectively, and the free volume of membranes is tuned from 5.567 to 6.253%. By optimization, the pervaporation performance of the membrane includes a 1-butanol separation factor of 37.9 and a total flux of 1179 g m–2 h–1 as evaluating 1.5 wt % 1-butanol/water solutions at 55 °C, which has a high superiority coupled with the fast reaction speed and oxygen insensitivity.