Functionalization of Syndiotactic Polystyrene via Superacid-Catalyzed Friedel–Crafts Alkylation
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Crystalline syndiotactic polystyrene (sPS) was functionalized by superacid-catalyzed Friedel–Crafts alkylation. Once a tertiary carbocation is generated by the reaction of tertiary alcohols and triflic acid, it subsequently reacted with aromatic ring of sPS, forming alkyl functionalized sPS. Various functional groups were incorporated into the phenyl ring of sPS using different substrates of tertiary alcohols including tertiary butanol, 2-methyl-2-butanol, and 2-methyl-2-hexanol. Degree of functionalization was conveniently tunable by changing the ratio of tertiary alcohol to styrene unit, and a maximum 80% of styrene rings was functionalized. Thermal properties of the functionalized sPSs were investigated by differential scanning calorimetry. Glass transition temperature and melting temperature of sPS were reduced after the modification.
KeywordsSyndiotactic polystyrene Superacid Friedel–Crafts alkylation Post-functionalization Crystalline polymer
Financial support from National Science Foundation (CHE 1534355) and U.S. Department of Energy (ARPA-E, IONICS DE-FOA-0001478) is greatly appreciated for C.B. G.N.K and S.L. also acknowledge the donors of the American Chemical Society Petroleum Research Fund for partial support of this research. The authors thank LG Chem Ltd. for providing sPS.
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