Polyisobutylene RAFT CTA by a click chemistry site transformation approach: Synthesis of poly(isobutylene-b-N-isopropylacrylamide)

Abstract

A novel block copolymer, composed of polyisobutylene (PIB) and poly(N-isopropylacrylamide) (PNIPAM) segments, was synthesized. The PIB block was prepared via quasiliving cationic polymerization and end-functionalized by in-situ quenching to yield telechelic halogen-terminated PIB. Azido functionality was obtained by displacement of the terminal halogen through nucleophilic substitution, which was confirmed by both 1H and 13C NMR. Coupling of an alkyne-functional chain transfer agent (CTA) to azido PIB was successfully accomplished through a copper-catalyzed click reaction. Structure of the resulting PIB-based macro-CTA was verified with 1H NMR, FTIR, and GPC, whereas coupling reaction kinetics were monitored by real-time variable temperature (VT) 1H NMR. Subsequently, the function of this macro-CTA was demonstrated by RAFT polymerization of NIPAM for synthesis of the second block. RAFT kinetics was investigated under a variety of reaction conditions using VT NMR, and the resulting block copolymers were characterized by 1H NMR and GPC. Aqueous solution properties were probed by dynamic light scattering confirming the presence of selfassembled aggregates with reversible temperature-sensitive responsiveness. © 2009 American Chemical Society.