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Synthesis of Thermally Switchable Poly(N-isopropylacrylamide-block-dendronized methacrylate)s

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journal contribution
posted on 23.01.2007, 00:00 by Caixia Cheng, Manfred Schmidt, Afang Zhang, A. Dieter Schlüter
A series of water-soluble linear diblock copolymers were synthesized, and their thermally switchable behavior under aqueous conditions was investigated. One block of these copolymers consists of poly(N-isopropylacrylamide) [poly(NiPAM)] and the other of positively charged first- and second-generation dendronized polymethacrylates [PG1 and PG2]. The copolymers were prepared via reversible addition−fragmentation chain transfer (RAFT) polymerization and the block lengths varied. The thermally switchable aggregation behavior of the copolymers was investigated by 1H NMR and fluorescence spectroscopy, and the lower critical aggregation temperatures (LCATs) were determined by turbidity measurements using UV/vis spectroscopy. Some of these block copolymers at elevated temperature formed supramolecular assemblies in the size range of 50−400 nm whose structures were investigated by transmission electron microscopy (TEM).