Improved Performance Of Nanocomposite Polyimide Membranes For Pervaporation Fabricated By Embedding Spirobisindane Structure-Functionalized Graphene Oxide

In this study, spirobisindane-functionalized graphene oxide (SFGO)/polyimide (Matrimid? 5218, i.e. M) solutions are spin-coated onto a polysulfone support to produce SFGO@M nanocomposite membranes for alcohol dehydration by pervaporation. Compounds 3,3,3?,3?-tetramethyl-1,1?-spirobisindane-6,6?-diol (TSD) and 4,4?((3,3,3?,3?-tetramethyl-2,2?,3,3?-tetrahydro-1,1?-spirobi[indene]-6,6?-diyl)bis(oxy))dianiline (TTSD) are synthesized based on a conversion reaction from bisphenol A (BPA). Both TSD and TTSD contain spirobisindane structure, which is inspired by the structural unit from polymers of intrinsic microporosity. The fine structural characteristics of SFGO@M membranes are evaluated using positron annihilation lifetime spectroscopy. The membrane free volume increases in the following order: M < GO@M < BPA-GO@M < TSD-GO@M < TTSDGO@M. These results reveal that SFGO affected the fine structural characteristics of membranes in a more significant manner when compared with GO@M and BPA-GO@M. Moreover, TSD-GO@M and TTSD-GO@M exhibit different levels of dehydration performance when tested on different alcohol feed solutions. After TTSD modification on GO, the membrane performance increased from 619.3 ? 124.0 g?m-2h- 1 for the pristine sample, to 915.5 ? 44.8 g?m-2h- 1 for TTSD-GO@M, and the water concentration in the permeate is maintained as high as 99 wt%. Furthermore, the modified membranes are stable under broad operating conditions with high potential for long-term use.