Polysulfone-Based Electrospun Anion Exchange Membranes

Nanofiber composite anion exchange membranes were prepared from crosslinked and quaternized polysulfone fibers embedded in a polysulfone matrix. Polysulfone with a mixture of chloromethyl and iodomethyl groups and containing a controlled amount of a diol crosslinker was simultaneously electrospun with polyphenylsulfone. The resultant anion exchange dual nanofiber mat was subsequently processed into a dense and defect-free membrane by: (i) compaction on a hydraulic press, (ii) heating to crosslink the chloromethyl/iodomethyl fibers, (iii) exposure to chloroform which softened the polyphenylsulfone and allowed it to flow between crosslinked fibers, and (iv) quaternization with trimethylamine. The final composite membrane exhibited good conductivity in room temperature water (54 mS/cm) with a water swelling of 118% and a wet membrane stress-at-break of 23 MPa. While the IEC of the quaternized nanofibers was higher than the polymer solubility limit in water, no weight loss was observed upon membrane equilibration in room temperature water, due to the presence of crosslinks.