Hyperbranch-Crosslinked S-SEBS Block Copolymer Membranes for Desalination by Pervaporation

Abstract

Sulfonated aromatic polymer (SAP) featuring hydrophilic nanochannels for water transport is a promising membrane material for desalination. SAPs with a high sulfonation degree favor water transport but suffer from reduced mechanical strength and membrane swelling. In this work, a hyperbranched polyester, H302, was introduced to crosslink a sulfonated styrene-ethylene/butylene-styrene (S-SEBS) copolymer membrane. The effects of crosslinking temperature and amount of H302 on the microstructure, and the pervaporation desalination performance of the membrane, were investigated. H302/S-SEBS copolymer membranes with different crosslinking conditions were characterized by various techniques including FTIR, DSC, EA, SEM, TEM and SAXS, and tensile strength, water sorption and contact angle measurements. The results indicate that the introduction of hyperbranched polyester enlarged the hydrophilic microdomain of the S-SEBS membrane. Crosslinking with hyperbranched polyester with heat treatment effectively enhanced the mechanical strength of the S-SEBS membrane, with the tensile strength being increased by 140–200% and the swelling ratio reduced by 45–70%, while reasonable water flux was maintained. When treating 5 wt% hypersaline water at 65 °C, the optimized crosslinked membrane containing 15 wt% H302 and heated at 100 °C reached a water flux of 9.3 kg·m−2·h−1 and a salt rejection of 99.9%. The results indicate that the hyperbranched-S-SEBS membrane is promising for use in PV desalination.

Keywords

• sulfonated styrene-ethylene/butylene-styrene copolymer
• hyperbranched polyester
• crosslinking
• pervaporation
• desalination