Cross-linking disulfonated poly(arylene ether sulfone) telechelic oligomers. 1. Synthesis, characterization, and membrane preparation

meta-Aminophenol was used during nucleophilic step copolymerization to end-cap partially disulfonated bisphenol A based random copolymers with controlled oligomeric molecular weights. The amine end groups were thermally reacted with a tetrafunctional epoxy reagent to produce networks. Very high gel fractions, up to 99%, and ductile film formation were achieved. The oligomer was further functionalized with acryloyl chloride, phenylethynyl phthalic anhydride, and maleic anhydride to obtain several novel free radically cross-linkable oligomers. The structure and molecular weights (M_n) were established with ¹H NMR spectroscopy of the oligomers and end groups. TGA analysis demonstrated the high thermal stability of these oligomers; DSC investigations showed that the oligomers had curing exotherms from 140 to 330 C and that residual casting solvent during cross-linking was necessary to avoid vitrification during membrane formation. In addition to the thermally cross-linkable systems, photocross-linking was demonstrated with the telechelic acrylamide functionalized oligomers. Two compositions were identified as potential candidates for further development. Cross-linking disulfonated poly(arylene ether sulfone) copolymers limits the high water sorption and swelling of these hydrophilic materials, which enhances several properties for membrane applications. Initial transport results indicate that cross-linking greatly reduces salt permeability while modestly decreasing water permeability, resulting in improved water/NaCl selectivity.