Homogeneous phase crosslinked poly(acrylonitrile-co-2-acrylamido-2-methyl-1-propanesulfonic acid) conetwork cation exchange membranes showing high electrochemical properties and electrodialysis performance

Herein, we report a simple process for the preparation of homogeneous crosslinked conetwork cation exchange membranes (CEMs). The synthesis strategy is based on sequential reaction of hydrazine hydrate and nitrile moieties of random copolymers of poly(acrylonitrile) and poly (2-acrylamido-2-methyl-1-propanesulfonic acid) (PAN-co-PAMPS). Copolymerization of the two monomers enhances miscibility between relatively hydrophobic PAN and hydrophilic ionic PAMPS domains which prevents microphase separation in the membrane matrices. The homogeneous phase co-continuous morphology with no microphase separation in the membrane matrices was confirmed by the homogeneous distribution of color solutes in the membrane matrices as well as by DSC, DMA, TEM, and AFM analyses. Both crosslinked (conetwork) and uncrosslinked copolymers (different composition) acted as CEMs. The CEMs were employed for desalination via electrodialysis. A representative crosslinked CEM (PAN-PAMPS-1) containing 15 mol% PAMPS exhibited the best desalination performance. Crosslinking of the copolymers improves the transport number, desalination performance, and lowers the power consumption of the membranes. This work thus highlights the benefit of crosslinking of ionic random amphiphilic copolymers to obtain CEMs with improved performance during desalination via electrodialysis.