Systematic Approaches To Tailor the Morphologies and Transport Properties of Solution-Cast Sulfonated Pentablock Copolymers AITranslate

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DOI：https://doi.org/10.1021/acsapm.8b00002

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Sulfonated block polymers are widely studied for applications in water management and electrochemical devices because they combine the properties of ionomers and thermoplastic elastomers in a single materials platform. Sulfonated block polymers are often processed into thin film membranes by casting from solution, and the resulting film morphology is strongly influenced by polymer–solvent interactions. In this work, we used mixtures of polar and nonpolar solvents to control solution-state interactions. We examined the self-assembled structures of solutions and corresponding films with small angle scattering and high-resolution microscopies. When the solvent mixture is selective to one block, the polymer self-assembles into lamellar phases in solution, and films cast from these solutions are also lamellar. On the other hand, a more neutral solvent mixture will produce a disordered structure in solution, leading to films with a disordered, network-like arrangement of lamellar domains. These distinct film morphologies are confirmed with measurements of transport properties; the transition from ordered lamellae to a disordered network produces a 2-fold increase in water uptake and 5-fold increase in proton conductivity at 52% relative humidity. These studies demonstrate that measurements of solution-state structure can inform process development, providing a simple route to achieve targeted film morphologies and transport properties.