Synthesis of Chiral Amphiphilic Diblock Copolymers via Consecutive RAFT Polymerizations and Their Aggregation Behavior in Aqueous Solution

Two chiral amphiphilic diblock copolymers with different relative lengths of the hydrophobic and hydrophilic blocks, poly(6-O-p-vinylbenzyl-1,2:3,4-Di-O-isopropylidene-D-galactopyranose)-b-poly(N-isopropylacrylamide) or poly(VBCPG)-b-poly(NIPAAM) and poly(20-(hydroxymethyl)-pregna-1,4-dien-3-one methacrylate)-b-poly(N-isopropylacrylamide) or poly(NMC-HPD)-b-poly(NIPAAM) were synthesized via consecutive reversible addition-fragmentation chain-transfer polymerizations of VBCPG or MAC-HPD and NIPAAM. The chemical structures of these diblock copolymers were characterized by H-1 nuclear magnetic resonance spectroscopy. These amphiphilic diblock copolymers could self-assemble into micelles in aqueous solution, and the morphologies of micelles were investigated by transmission electron microscopy. By comparison with the lower critical solution temperatures (LCST) of poly (NIPAAM) homopolymer in deionized water (32 degrees C), a higher LCST of the chiral amphiphilic diblock copolymer (poly(VBCPG)-b-poly(NIPAAM)) was observed and the LCST increased with the relative length of the poly(VBCPG) block in the copolymer from 35 to 47 degrees C, respectively. (C) 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 7690-7701, 2008