SEARCH

SEARCH BY CITATION

Keywords:

  • anionic polymerization;
  • cloud point;
  • living polymerization;
  • poly(N-isopropylacrylamide);
  • stereoregularity

Abstract

Anionic polymerization of N-methoxymethyl-N-isopropylacrylamide (1) was carried out with 1,1-diphenyl-3-methylpentyllithium and diphenylmethyllithium, -potassium, and -cesium in THF at −78 °C for 2 h in the presence of Et2Zn. The poly(1)s were quantitatively obtained and possessed the predicted molecular weights based on the feed molar ratios between monomer to initiators and narrow molecular weight distributions (Mw/Mn = 1.1). The living character of propagating carbanion of poly(1) either at 0 or −78 °C was confirmed by the quantitative efficiency of the sequential block copolymerization using N,N-diethylacrylamide as a second monomer. The methoxymethyl group of the resulting poly(1) was completely removed to give a well-defined poly(N-isopropylacrylamide), poly(NIPAM), via the acidic hydrolysis. The racemo diad contents in the poly(NIPAM)s could be widely changed from 15 to 83% by choosing the initiator systems for 1. The poly(NIPAM)s obtained with Li+/Et2Zn initiator system possessed syndiotactic-rich configurations (r = 75–83%), while either atactic (r = 50%) or isotactic poly(NIPAM) (r = 15–22%) was generated with K+/Et2Zn or Li+/LiCl initiator system, respectively. Atactic and syndiotactic poly(NIPAM)s (42 < r < 83%) were water-soluble, whereas isotactic-rich one (r < 31%) was insoluble in water. The cloud points of the aqueous solution of poly(NIPAM)s increased from 32 to 37 °C with the r-contents. These indicated the significant effect of stereoregularity of the poly(NIPAM) on the water-solubility and the cloud point in water © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 4832–4845, 2006