Effect of Backbone Structure, Degree of Sulfonation and Crosslinking On Water Permeability and Salt Selectivity for Poly(arylene ether sulfone) Random Copolymers

Collaboration between Virginia Tech and the University of Texas Austin has demonstrated that disulfonated poly(arylene ether sulfones) are an attractive candidates for several water purification processes.  Notably, the sulfonated copolymers have a high chlorine resistance compared to the state-of-the-art crosslinked polyamide thin film composite.  These materials have demonstrated high water permeability, but sodium chloride rejection needs to be further improved for reverse osmosis applications.  A systematic series of controlled molecular weight 4,4’-biphenol and bisphenol-A based partially disulfonated polysulfones were synthesized with amine terminated endgroups, which could be further functionalized to afford acrylamide, phenylethynyl phthalic anhydride and maleic anhydride crosslinkable oligomers.  Gel fractions up to 90% were achieved in many cases, effectively reducing the swelling of the membrane in water and leading to enhanced salt rejection.  Several systematic series of crosslinked copolymers with varying degrees of sulfonation were investigated for their transport properties, which varied widely from the linear control series.  These crosslinked materials were prepared as dense films, however preparation of thin film (and asymmetric membranes) composites will also be discussed.