Preparation of quadruple responsive polymeric micelles combining temperature-, pH-, redox-, and UV-responsive behaviors and its application in controlled release system

A novel series of quadruple responsive copolymers, poly(ethylene glycol)-ss-[poly(dimethylaminoethyl methacrylate)-co-poly(2-nitrobenzyl methacrylate)] [PEG-ss-(PDMAEMA-co-PNBM)], were synthesized via atom transfer radical polymerization mediated by home-made PEG-based macro-initiator labeled with disulfides. The obtained copolymers could self-assemble in aqueous solution forming micelles with the disulfide bridge linking the hydrophilic coronas (PEG) and the hydrophobic cores (PDMAEMA-co-PNBM). Investigation on the resulted micelles indicated that the micelles could respond to various stimuli, that is, temperature, pH, the presence of dithiothreitol (DTT), and UV irradiation. Moreover, the responsive behavior of the micelles depends on the type of stimuli, that is, temperature change causes size change of the micelles, while UV irradiation leads to dissolution of the self-assembled structures. Such stimulus-dependent responsive behavior could be applied in smart materials that deal with multi-tasks or in the construction of complex logic gate. The potential application of the multi-responsive micelles in cargo release system was also evaluated using Nile Red (NR) as model molecule.