Living anionic polymerization of <i>N</i>‐methoxymethyl‐<i>N</i>‐isopropylacrylamide: Synthesis of well‐defined poly(<i>N</i>‐isopropylacrylamide) having various stereoregularity

Abstract

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 Et 2 Zn. 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 ( M w / M n = 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 + /Et 2 Zn 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 + /Et 2 Zn or Li + /LiCl initiator system, respectively. Atactic and syndiotactic poly(NIPAM)s (42 &lt; r &lt; 83%) were water‐soluble, whereas isotactic‐rich one ( r &lt; 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