PDMAEMA-b-PPOA-b-PDMAEMA double-bond-containing amphiphilic triblock copolymer: synthesis, characterization, and pH-responsive self-assembly

A series of ABA amphiphilic triblock copolymers consisting of hydrophobic double-bond-containing poly(phenoxyallene) (PPOA) and hydrophilic poly(2-(dimethylamino) ethyl methacrylate) (PDMAEMA) segments was synthesized by successive free radical polymerization and single-electron-transfer living radical polymerization (SET-LRP) via the site transformation strategy. Conventional free-radical homopolymerization of phenoxyallene with a cumulated double bond was first initiated by the azo group in a new bifunctional initiator comprising a Br-containing SET-LRP initiating group simultaneously for providing a polyallene-based macroinitiator, Br-PPOA-Br, bearing SET-LRP initiating groups at both ends. The target triblock copolymer of PDMAEMA-b-PPOA-b-PDMAEMA was then obtained by SET-LRP of DMAEMA initiated by the Br-PPOA-Br macroinitiator. Critical micelle concentration (cmc) of PDMAEMA-b-PPOA-b-PDMAEMA amphiphilic triblock copolymer in aqueous media was determined via fluorescence spectroscopy using N-phenyl-1-naphthylamine as a probe, which was dependent on pH and salinity of the aqueous solution. Furthermore, via transmission electron microscopy, PDMAEMA-b-PPOA-bPDMAEMA amphiphilic triblock copolymers were found to self-assemble into spherical micelles in aqueous media.