Cross‐Linked Poly(Styrene‐Co‐Styrene Sulfonate) Membranes: Effect of Crosslinking on Proton Conductivity and Physicochemical Properties

In the present study, cross‐linked poly(styrene‐co‐styrene sulfonate), poly(Sty‐co‐StyS) membranes are prepared using divinylbenzene (DVB) cross‐linker at different weight percentages via free‐radical polymerization in order to achieve desirable proton conductivity and mechanical properties for proton exchange membrane (PEM) water electrolyzer applications. The role of crosslinker in the membrane is also investigated by conducting a comparison study using the membrane without cross‐linker. The cross‐linked poly(Sty‐co‐StyS) membrane exhibits enhanced thermal stability compared to the non‐cross‐linked membrane as revealed by thermal analysis. The sulfonated copolymer showed good solubility and film formation ability in a suitable solvent and composition. The proton conductivities of all the synthesized membranes range between 10 −3 and 10 −2 S/cm, and the other physico‐chemical properties of the membranes were also studied. Among all the membranes, the cross‐linked poly(Sty‐co‐StyS) membrane with 1% crosslinker showed the proton conductivity as high as 1.57 × 10 −2 S/cm, water uptake of 38.2%, and ion exchange capacity of 2.7 mmol/g and excellent thermal stability up to 450°C.