Abstract
Anionic polymerization of N-methoxymethyl-N-isopropylacrylamide (1) was carried out with diphenylmethyllithium,-potassium and-cesium in the presence of diethylzinc in THF at-78°C for 1-3 h. The resulting poly(1)s possessed the predicted molecular weights based on the molar ratios between monomer and initiators and the narrow molecular weight distributions (M w/M n = 1.1). The methoxymethyl protecting groups were completely hydrolyzed to afford a poly(N-isopropylacrylamide) (poly(NIPAM)), having well-defined chain structures by treatment with aqueous HCl in 1,4-dioxane at room temperature for 12 h. Stereoregularity of the resulting poly(NIPAM) was strongly affected by the counterions of anionic initiator. From the 1H-NMR measurement, the racemo dyad of poly(NIPAM) obtained with diphenylmethyllithium, -potassium and -cesium in the presence of Et2Zn was found to be 75, 50 and 30%, respectively. The sequential copolymerization of styrene or isoprene with 1 and the subsequent deprotection quantitatively gave well-defined block copolymers containing poly(NIPAM) segments. The copolymers had the predicted molecular weights, compositions and the narrow molecular weight distributions, and showed the typical amphiphilic character with regard to solubility.
Published Version
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