Sulfonated Poly(arylene sulfide sulfone nitrile) Multiblock Copolymers with Ordered Morphology for Proton Exchange Membranes

Ordered morphologies in disulfonated poly(arylene sulfide sulfone nitrile) (SPSN) copolymers were generated via thermal annealing followed by multiblock copolymer synthesis. While SPSN random copolymers (R-SPSN) showed featureless morphologies, the SPSN multiblock copolymers (B-SPSN) exhibited cocontinuous lamellar morphologies with a center-to-center interdomain size of up to 40 nm. In spite of the well-ordered, interconnected hydrophilic domains, the water self-diffusion coefficient (e.g., D = (0.7–2.0) × 10 –10 m 2 s –1 ) and proton conductivity (e.g., σ = 0.16–0.20 S cm –1 in deionized water at 30 °C) through B-SPSN were lower than those of the corresponding R-SPSN (e.g., D = (3.5–3.9) × 10 –10 m 2 s –1 and σ = 0.21 S cm –1 ) due to the relatively lower water uptake of the B-SPSN after thermal annealing. The reduced water uptake of B-SPSN was beneficial to reduction of peroxide degradation rate. Thermal annealing produced significant gains in morphological ordering and finer control over desired membrane properties for proton conduction applications.