Zwitterionic ring-opening polymerization for the facile, efficient and versatile grafting of functional polyethers onto graphene sheets

• Polyethers are covalently anchored to thermally reduced graphite oxide sheets.
• Zwitterionic ring-opening polymerization of epoxides with B(C6F5)3 is employed.
• Macro- and micro-wettability of functionalized graphene sheets are compared.
• Dispersion of functionalized graphene sheets in a polymer matrix is evaluated.
• Crystallinity of grafted polymer is evaluated.

Zwitterionic ring-opening polymerization is used as a strategy to covalently anchor polyethers of different chemical nature and polarity onto thermally reduced graphene oxide (rGO) sheets. This versatile strategy involves the generation of a macrozwitterionic propagating species by reaction of a functional epoxide monomer with a Lewis acid catalyst, B(C6F5)3. Upon addition of rGO sheets, the polyether propagating species react with available nucleophilic groups on the rGO surface to generate graphene sheets decorated with functional polyether chains in amounts as large as 30 wt%. Polyethers obtained from glycidyl monomers carrying hydroxyl, hexadecyl and fluorinated groups, as well as a copolyether of tetrahydrofuran and glycidyl phenyl ether, were successfully grafted to rGO sheets. Surprisingly, grafting was found to increase the degree of hydrophilicity of the rGO sheets, irrespective of the hydrophobic or hydrophilic character of the side groups attached to the main polyether chain, as determined from contact angle measurements in both macroscopic and microscopic experiments. Properties such as the degree of crystallization of poly(tetrahydrofuran) grafted onto rGO sheets and the transparency of polymer films containing polyether-grafted rGO sheets were also evaluated in this study.

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