Self-assembly of pH-responsive and fluorescent comb-like amphiphilic copolymers in aqueous media

Abstract

“Comb-like” graft copolymers, consisting of a poly((N-vinylcarbazole)-co-(4-vinylbenzyl chloride)) (P(NVK-co-VBC)) copolymer backbone from free radical polymerization and poly(((2-dimethylamino)ethyl methacrylate)-co-(tert-butyl acrylate)) (P(DMAEMA-co-tBA)) side chains from atom transfer radical polymerization (ATRP), were hydrolyzed to produce the acrylic acid (AAc)-containing “comb-like” graft copolymers of P(NVK-co-VBC)-comb-P(DMAEMA-co-AAc). The amphiphilic copolymers possess a fluorescent hydrophobic P(NVK-co-VBC) backbone and pH-sensitive hydrophilic P(DMAEMA-co-AAc) side chains. Arising from acid–base interaction of the hydrophilic side chains, the copolymers can self-assemble into pH-responsive fluorescent and multi-walled hollow vesicles of well-defined morphology in aqueous media. The size and layered wall thickness of the vesicles are also dependent on the length of the copolymer side chains, while the number of wall layers is dependent on the concentration of the vesicles in the aqueous media. In comparison, a N-isopropylacrylamide (NIPAAm)-containing comb-like amphiphilic copolymer (P(NVK-co-VBC)-comb-P(NIPAAm-co-DMAEMA)) of similar structure, albeit with non-interacting hydropholic side chains, self-assembles only into temperature and pH-responsive single-shelled hollow nanoparticles in aqueous media.