Synthesis and self-assembly of a fluorine-containing amphiphilic graft copolymer bearing a perfluorocyclobutyl aryl ether-based backbone and poly(acrylic acid) side chains

A series of fluorine-containing amphiphilic graft copolymers consisting of a semi-fluorinated poly(2-methyl-1,4-bistrifluorovinyloxybenzene) (PMBTFVB) backbone and hydrophilic poly(acrylic acid) (PAA) side chains was synthesized by the combination of thermal cycloaddition polymerization and atom transfer radical polymerization (ATRP) through the grafting-from strategy. 2-Methyl-1,4-bistrifluorovinyloxybenzene was first homopolymerized via thermal step-growth [2π + 2π] cycloaddition polymerization to form a perfluorocyclobutyl aryl ether-based backbone. This fluoropolymer was transformed into the macroinitiator with the controllable density of the initiating functionality by the mono-bromination of pendant methyls. The target PMBTFVB-g-PAA amphiphilic graft copolymers were achieved by ATRP of tert-butyl acrylate initiated by the macroinitiator followed by the acidolysis of hydrophobic PtBA side chains into hydrophilic PAA segments. Critical micelle concentrations (cmc) of these amphiphilic graft copolymers were determined by fluorescence spectroscopy using N-phenyl-1-naphthylamine as fluorescent probe. Self-assembly behaviors of these fluorine-containing amphiphilic graft copolymers in aqueous media were investigated by transmission electron microscopy (TEM). Diverse micellar morphologies including vesicular, worm-like, and bowl-shaped nanostructures were obtained through tuning the water content and the length of PAA side chain.