Post-Hydration Crosslinking of Ion Exchange Membranes to Control Water Content

Crosslinking is a common approach toward mitigating excess water uptake by ion exchange membranes. Most crosslinking reactions are performed when the ionomer is in anhydrous form, before the membrane self-segregates into hydrophilic and hydrophobic domains upon exposure to water. Here we use numerical and molecular simulations to investigate the prospect of crosslinking the polymer after casting and partial hydration of the membrane at subsaturated conditions. Such a process would allow the membranes to develop their nanosegregated morphology and establish well-connected but narrow water channels, while limiting further sorption of water. We find that post-hydration crosslinking of membranes has the ability to dramatically reduce membrane swelling. These results show that crosslinking after membrane casting and hydration may be a viable option for controlling water uptake. Further, we suggest chemical crosslinking strategies that may yield sufficiently high membrane gel fractions based on our analyses.