Photo-induced sol–gel processing for low-temperature fabrication of high-performance silsesquioxane membranes for use in molecular separation

Abstract

Silsesquioxane (SQ) membranes derived from 3-methacryloxypropyltrimethoxysilane and bis(trimethoxysilyl)ethane were successfully fabricated at low temperature via photo-induced sol-gel processing. Radical and cationic polymerization of SQ membranes showed high degrees of separation factor and permeance for water/isopropanol separation in pervaporation.

Photo-induced sol–gel synthesis of polymer-supported silsesquioxane membranes

“…The peak areas of the methoxy groups decreased very fast in the rst 15 s and approached a steady value, while simultaneously the peak areas of the silanol groups increased markedly, suggesting that the photo-acid catalyzed hydrolysis of methoxy groups was completed within a very short period of UV irradiation. 17 Aer hydrolysis of the methoxy groups, a subsequent condensation of silanol groups occurred quickly to form the cross-linked structure, as conrmed by the pencil hardness measurement. These results indicate that the photo-induced sol-gel processing initiated by the generation of photo-acid can be used to prepare silsesquioxane thin lms with hard and crosslinked structures within a very short period of UV irradiation without elevating the processing temperature.…”

“…Details of the procedure for sol preparation are described in a previous report. 17 The concentration of the sols was 1.0 wt%, and the molar ratios of BTMSE : H 2 O : AcOH and BTESE : H 2 O : AcOH for sol preparation were 1 : 3 : 0.3 and 1 : 60 : 0.3, respectively. The reaction times for BTMSE-and BTESE-derived sols were 1 and 11 h, respectively.…”

“…In our previous work, the ceramic-supported BTMSE-derived membrane prepared with the same photo-induced sol-gel process showed a separation factor of several hundreds. 17 Therefore, if the BTMSE-derived layer was formed properly, the polymer-supported BTMSE-derived membrane should have had a similar separation performance.…”

“…15,16 Previously, we proposed photo-induced cationic polymerization for the fabrication of ceramicsupported silsesquioxane membranes. 17 To obtain a crosslinked structure at low temperature without ring, we coated silsesquioxane sols onto porous ceramic supports together with a photo-acid generator (PAG), and then irradiated the dried gel with UV light to generate a photo-acid that would induce further polymerization in the coated layer via acid-catalyzed reactions. 17 The obtained membrane showed a high separation factor of 525 and a water ux of 3.12 kg m À2 h À1 during the pervaporation of 90 wt% isopropanol-water mixtures at 40 C. 17 As an extension of this achievement, in this work, we applied a photo-induced sol-gel process for fabricating polymer-supported silsesquioxane membranes.…”

Organosilica-Based Membranes in Gas and Liquid-Phase Separation

“…Instead of calcination of gels by thermal treatment, a novel approach via photo-induced processing was developed to prepare polymer-supported organosilica membranes at room temperature [46,47]. The effect of UV irradiation on the network formation is important.…”