Synthesis and characterization of polystyrene-b-poly(ethylene oxide)-b-polystyrene triblock copolymers by atom-transfer radical polymerization

Well-defined polystyrene (PS)-b-poly(ethylene oxide) (PEO)-b-PS triblock co polymers were synthesized by atom-transfer radical polymerization (ATRP), u sing C-X-end-group PEO as macroinitiators. The triblock copolymers were cha racterized by infrared spectroscopy, nuclear magnetic resonance spectroscop y, and gel permeation chromatography. The experimental results showed that the polymerization was controlled/living. It was found that when the number -average molecular weight of the macroinititors increased from 2000 to 10,0 00, the molecular weight distribution of the triblock copolymers decreased roughly from 1.49 to 1.07 and the rate of polymerization became much slower . The possible polymerization mechanism is discussed. According to the Cu c ontent measured with atomic absorption spectrometry, the removal of catalys ts, with CHCl3 as the solvent and kaolin as the in situ absorption agent, w as effective. (C) 2000 John Wiley & Sons, Inc.