Thermo- and pH-induced self-assembly of P(AA-b -NIPAAm-b -AA) triblock copolymers synthesized via RAFT polymerization

Abstract

A series of environmentally sensitive ABA triblock copolymers with different block lengths were prepared by reversible addition-fragmentation chain transfer (RAFT) polymerization from acrylic acid (AA) and N-isopropylacrylamide (NIPAAm). The GPC and 1H NMR analyses demonstrated the narrow molecular weight distribution and precise chemical structure of the prepared P(AA-b-NIPAAm-b-AA) triblock copolymers owing to the controlled/living characteristics of RAFT polymerization. The lower critical solution temperature (LCST) of the triblock copolymers could be tailored by adjusting the length of PAA block and controlled by the pH value. Under heating, the triblock copolymers underwent self-assemble in dilute aqueous solution and formed nanoparticles revealed via TEM images. Physically crosslinked nanogels induced by inter-/intra-hydrogen bonding or core-shell micelle particles thus could be obtained by changing environmental conditions. With a well-defined structure and stimuli-responsive properties, the P(AA-b-NIPAAm-b-AA) copolymer is expected to be employed as a nanocarrier for biomedical applications in controlled-drug delivery and targeting therapy. © 2015 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2016, 54, 1109–1118