Synthesis of well-defined block copolymers containing poly(N-isopropylacrylamide) segment by anionic block copolymerization of N-methoxymethyl-N-isopropylacrylamide
Synthesis of well-defined block copolymers containing poly(N-isopropylacrylamide) segment by anionic block copolymerization of N-methoxymethyl-N-isopropylacrylamide
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DOI：
10.1163/156855504322890016
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发表时间：
2004-01
影响因子：
1.6
通讯作者：
Mana Ito;Takashi Ishizone
中科院分区：
文献类型：
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作者：
Mana Ito;Takashi Ishizone
N-甲氧基甲基-N-异丙基丙烯酰胺（1）与二苯基甲基锂、钾和铯在二乙基锌存在下于THF中于-78 ℃进行阴离子聚合1-3 h。所得聚（1）具有基于单体与引发剂之间的摩尔比的预测分子量和窄的分子量分布（Mw/Mn = 1.1）。将甲氧基甲基保护基完全水解，得到聚（N-异丙基丙烯酰胺）（聚（NIPAM）），其通过在室温下用HCl水溶液在1，4-二氧六环中处理12小时而具有明确的链结构。聚（NIPAM）的立构规整性受到阴离子引发剂的反离子的强烈影响。从1H-NMR测量，聚（NIPAM）与二苯基甲基锂，-钾和-铯在Et 2 Zn的存在下得到的外消旋二联体被发现分别为75，50和30%。苯乙烯或异戊二烯与1的顺序共聚和随后的脱保护定量地给出了定义明确的嵌段共聚物含有聚（NIPAM）片段。该共聚物具有预测的分子量、组成和窄的分子量分布，并且在溶解性方面显示出典型的两亲性。
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.