Synthesis of dual thermoresponsive ABA triblock copolymers by both living cationic vinyl polymerization and RAFT polymerization using a dicarboxylic RAFT agent
Synthesis of dual thermoresponsive ABA triblock copolymers by both living cationic vinyl polymerization and RAFT polymerization using a dicarboxylic RAFT agent
复制标题
DOI：
10.1016/j.polymer.2012.12.039
复制
发表时间：
2013-02
期刊：
影响因子：
4.6
通讯作者：
S. Sugihara;K. Iwata;S. Miura;A. H. Ma’Radzi;Y. Maeda
中科院分区：
文献类型：
--
作者：
S. Sugihara;K. Iwata;S. Miura;A. H. Ma’Radzi;Y. Maeda
为了阐明AB二嵌段共聚物和阿坝三嵌段共聚物形成胶束的差异，通过MOVE的活性阳离子聚合和使用二羧酸RAFT试剂的NIPAM的RAFT聚合来合成PMOVE-PNIPAM-PMOVE三嵌段共聚物，其中MOVE是2-甲氧基乙基乙烯基醚，NIPAM是N-异丙基丙烯酰胺。阿坝三嵌段共聚物由阳离子可聚合单体（A）MOVE和自由基可聚合单体（B）NIPAM组成。采用二元RAFT试剂/SnBr 4引发体系进行活性阳离子聚合是三嵌段共聚成功的关键。阳离子聚合同时引发两个质子每一个二羧酸RAFT试剂。在阳离子聚合之后，使聚合淬灭，然后在约20 ° C下同时回收RAFT羧酸根抗衡阴离子。86%的效率，随后是RAFT聚合。所得PMOVE-PNIPAM-PMOVE三嵌段共聚物含有两个温敏嵌段。所得嵌段共聚物在水中可逆地形成或变形胶束组装体。当核形成嵌段PNIPAM的链长增加时，总是获得更大的胶束。三嵌段胶束的尺寸大于相应的二嵌段胶束的尺寸。浓溶液中胶束形成物理凝胶，三嵌段胶束的最小凝胶浓度低于相应的二嵌段胶束。
To elucidate a difference of micelles formed from AB di- and ABA tri-block copolymers, PMOVE–PNIPAM–PMOVE triblock copolymers were synthesized by both living cationic polymerization of MOVE and RAFT polymerization of NIPAM using a dicarboxylic RAFT agent, where MOVE is 2-methoxyethyl vinyl ether, NIPAM is N-isopropylacrylamide. The ABA triblock copolymers consist of cationically polymerizable monomer (A), MOVE, and radically polymerizable monomer (B), NIPAM. The key to success in the triblock copolymerization is to utilize a dicarboxylic RAFT agent/SnBr4initiation system for living cationic polymerization. The cationic polymerization was simultaneously initiated from two protons per one dicarboxylic RAFT agent. After the cationic polymerization, the polymerization was quenched and then the RAFT carboxylate counter anion was concurrently recovered at ca. 86% efficiency, followed by the RAFT polymerization. The resulting PMOVE–PNIPAM–PMOVE triblock copolymers contain two thermoresponsive blocks. The resulting block copolymers reversibly formed or deformed micellar assemblies in water. When the chain length of the core-forming block, PNIPAM, is increased, larger micelles were invariably obtained. The triblock micellar size was larger than that of the corresponding diblock micelle. The micelles at the concentrated solution formed physical gel, and the minimum gelation concentration of the triblock micelles was lower than that of the corresponding diblock micelles.