Micelles possessing mixed cores and thermoresponsive shells fabricated from well‐defined amphiphilic ABC miktoarm star terpolymers

Abstract

Abstract Amphiphilic ABC miktoarm star terpolymers consisting of polystyrene, poly(ε‐caprolactone), and poly( N ‐isopropylacrylamide) arms, PS(‐ b ‐PNIPAM)‐ b ‐PCL, were synthesized via a combination of atom transfer radical polymerization, ring‐opening polymerization (ROP), and click chemistry. Difunctional PS bearing an alkynyl and a primary hydroxyl moiety at the chain end, PS‐ alknyl ‐ OH , was prepared by reacting azido‐terminated PS with an excess of 3,5‐bis(propargyloxy)benzyl alcohol (BPBA) under click conditions. The subsequent ROP of ε‐caprolactone using PS‐ alknyl ‐ OH macroinitiator afforded PS(‐ alkynyl )‐ b ‐PCL copolymer bearing an alkynyl moiety at the diblock junction point. Target PS(‐ b ‐PNIPAM)‐ b ‐PCL amphiphilic ABC miktoarm star terpolymers were then prepared via click reaction between PS(‐ alkynyl )‐ b ‐PCL and an excess of azido‐terminated PNIPAM (PNIPAM‐ N 3 ). The removal of excess PNIPAM‐ N 3 was accomplished by “clicking” onto alkynyl‐functionalized Wang resin. All the intermediate and final products were characterized by gel permeation chromatography, 1 H NMR, and FTIR. In aqueous solution, the obtained amphiphilic ABC miktoarm star terpolymer self‐assembles into micelles possessing mixed PS/PCL cores and thermoresponsive shells, which were further characterized by dynamic laser light scattering and transmission electron microscopy. © 2009 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 47: 1636–1650, 2009