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., <i>D</i> = (0.7–2.0) × 10^–10 m² 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., <i>D</i> = (3.5–3.9) × 10^–10 m² 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