Well-defined thermosensitive, water-soluble polyacrylates and polystyrenics with short pendant oligo (ethylene glycol) groups synthesized by nitroxide-mediated radical polymerization

摘要

We report the synthesis and thermosensitive properties of well-defined water-soluble polyacrylates and polystyrenics with short pendant oligo(ethylene glycol) groups. Four monomers, methoxydi(ethylene glycol) acrylate (DEGMA), methoxytri(ethylene glycol) acrylate (TEGMA), alpha-hydro-omega-(4-vinylbenzyl)tris(oxyethylene) (HTEGSt), and alpha-hydro-omega-(4-vinylbenzyl)tetrakis(oxyethylene) (HTrEGSt), were prepared and polymerized by nitroxide-mediated radical polymerization with 2,2,5-trimethyl-3-(1-phenylethoxy)-4-phenyl-3-azahexane as an initiator. Kinetics and gel permeation chromatography analysis showed that the polymerizations were controlled processes yielding polymers with controlled molecular weights and narrow polydispersities. All polymers could be dissolved in water, forming transparent solutions, and undergo phase transitions when the temperature was above a critical point. The thermosensitive properties were studied by turbidimetry and variable-temperature H-1 NMR spectroscopy. The cloud points of the polymers of DEGMA, TEGMA, HTEGSt, and HTrEGSt were around 38, 58, 13, and 64 degrees C, respectively. For all four polymers, the cloud point increased with decreasing concentration and increasing molecular weight in the studied molecular weight range of 5000-30,000 g/mol. The removal of the nitroxide group from the polymer chain end resulted in a higher cloud point. (c) 2006 Wiley Periodicals, Inc.