Diverse Thermoresponsive Behaviors of Uncharged UCST Block Copolymer Micelles in Physiological Medium

Three amphiphilic diblock copolymers, representative of three types of block copolymer (BCP) design, were synthesized using reversible addition–fragmentation chain-transfer (RAFT) polymerization. All of them have a same uncharged block of a random copolymer of commercially available acrylamide and acrylonitrile, P(AAm-co-AN), and exhibit a composition-tunable upper critical solution temperature (UCST). We show that by coupling a common P(AAm-co-AN) block with either hydrophobic polystyrene (PS) or hydrophilic poly(dimethylacrylamide) (PDMA) or the lower critical solution temperature (LCST) polymer of poly(N,N-dimethylaminoethyl methacrylate) (PDMAEMA), the BCP micelles formed in water or in phosphate buffered saline (PBS) can display diverse and UCST-dictated changes in response to temperature variations, such as the reversible dispersion-aggregation of micelles, dissolution-formation of micelles, and reversal of micelle core and corona. The results point out that P(AAm-co-AN) is a robust UCST polymer tha...