Ultraviolet light-breakable and tunable thermoresponsive amphiphilic block copolymer: from self-assembly, disassembly to re-self-assembly

Abstract

Novel ultraviolet (UV) light-breakable and tunable thermoresponsive amphiphilic block copolymers were synthesized by atom transfer radical polymerization (ATRP). These amphiphilic copolymers can self-assemble into micelles in water. The lower critical solution temperature (LCST) and size of the micelles were adjusted by altering the ratio of 2-(2-methoxyethoxy)ethyl methacrylate (MEO₂MA) and oligo(ethylene glycol) methacrylate (OEGMA). Upon UV light irradiation, 2-nitrobenzyl moieties were detached from polymer chains and the micelles were dissociated. When the solutions were heated above LCST, the micelles can be re-self-assembled. Investigation revealed that the Nile red molecules which were encapsulated in micelles can be controllably released through changing temperature and undergoing UV light irradiation of micelle solutions.