Department of Polymer Chemistry, Graduate School of Engineering, Kyoto University, Nishikyo-ku, Kyoto, 615-8510, Japan.
Precursory Research for Embryonic Science and Technology (PRESTO), Japan Science and Technology Agency (JST), 4-1-8 Kawaguchi, Saitama, 332-0012, Japan.
Angew Chem Int Ed Engl. 2016 Nov 14;55(47):14584-14589. doi: 10.1002/anie.201607169. Epub 2016 Oct 20.
By utilizing features of the hemiacetal ester (HAE) bond: easy formation from vinyl ether and carboxylic acid and easy cleavage into different functional groups (-COOH and -OH), we achieved control of the alternating sequence of two functional pendant groups of a vinyl copolymer. Methacrylate- and acrylate-based vinyl groups were connected through HAE bonds to prepare a cleavable divinyl monomer, which was cyclo-polymerized under optimized conditions in a ruthenium-catalyzed living radical polymerization. Subsequent cleavage of the HAE bonds in the resultant cyclo-pendant led to a copolymer consisting of alternating methacrylic acid and 2-hydroxyethyl acrylate units as analyzed by C NMR spectroscopy. The alternating sequence of -COOH and -OH pendants specifically provided a lower critical solution temperature (LCST) in an ether solvent, which was not observed with the random copolymer of same composition ratio.
利用半缩醛酯 (HAE) 键的特性：易于从乙烯基醚和羧酸形成，易于裂解成不同的官能团（-COOH 和 -OH），我们实现了对两个官能团侧基的交替序列的控制。通过 HAE 键将基于甲基丙烯酸酯和丙烯酸酯的乙烯基基团连接起来，制备可裂解的二乙烯基单体，然后在优化条件下在钌催化的活性自由基聚合中环化。通过 13 C NMR 光谱分析，所得环接枝物中的 HAE 键的裂解导致交替的甲基丙烯酸和 2-羟乙基丙烯酸单元的共聚物的形成。-COOH 和 -OH 侧基的交替序列特别在醚溶剂中提供了较低的临界溶解温度（LCST），而在相同组成比的无规共聚物中则没有观察到。
