Synthesis of poly (methyl methacrylate)-b-polystyrene with high molecular weight by DPE seeded emulsion polymerization and its application in proton exchange membrane

• PMMA-b-PS with different molecular weight and block ratios were synthesized by DPE seeded emulsion polymerization.
• Polymerization kinetics was investigated and homogeneous latex particles were obtained.
• Lamella morphology of microphase separation formed in block copolymer with symmetric structure.
• Membranes were casted from sulfonated block copolymers with different sulfonation degree.
• Membranes owned fine proton conductivity and were candidates as proton exchange membranes.

In this article, we present poly (methyl methacrylate)-b-polystyrene (PMMA-b-PS) with different block ratios and high molecular weight, which was synthesized by environmentally friendly seeded emulsion polymerization with 1,1-diphenylethylene (DPE) as a chain transfer agent. Polymerization kinetics in the first and second stage was investigated. Stable latex and homogeneous latex particles were obtained with the characterization of laser light scattering (LLS) and transmission electron microscopy (TEM). SEC and 1H NMR revealed the successful preparation of block copolymers with high molecular weight and two different block ratios. The morphology of microphase separation of block copolymer thin films was investigated by AFM, and long-range order lamellar morphology was observed after vapor-annealing. The block copolymer with block ratio of almost 1:1 and higher molecular weight than that of previous PMMA-b-PS was sulfonated with acetyl sulfate, and the sulfonation was confirmed by FTIR, 1H NMR, and TGA. Then, the sulfonated PMMA-b-PS was casted as membranes. The electrochemical impedance spectroscopy displayed that membranes possessed favorable proton conductivity and fine dimensional stability, and they could be candidates as proton exchange membranes.

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