Treelike Polymeric Ionic Liquids Grafted onto Graphene Nanosheets

Abstract

Herein we report on a versatile grafting-to process combined with end group modification to prepare treelike polymeric ionic liquids which are covalently attached to graphene nanosheets. When cationic 3-ethyl-3-hydroxymethyloxetane (EHO) polymerization is initiated in the presence of dispersed hydroxy-functional graphene (FG) nanosheets, chain termination reactions account for highly effective grafting of hyperbranched poly(3-ethyl-3-hydroxymethyloxetane) (PEHO) onto FG. Tosylated PEHO hydroxy end groups are highly reactive alkylating agents for N-alkylimidazoles, thus enabling the incorporation of alkylimidazolium cations with tosylate counteranions as outer shell of the treelike FG-PEHO graft copolymer. In sharp contrast to FG, treelike FG-PEHO containing methylimidazolium tosylates as shell are readily dispersed in water to form stable dispersions without requiring either surfactant addition or high shear mixing. Moreover, these novel carbon/polymer hybrid materials self-assemble on surfaces and form films. In view of the facile tuning of their structures and properties, such treelike graphene polyelectolytes qualify for manifold applications.