Ogura Michihiro, Tokuda Hiroyuki, Imabayashi Shin-ichiro, Watanabe Masayoshi
Department of Chemistry and Biotechnology, Yokohama National University, Tokiwadai, Hodogaya-ku, Yokohama, Japan.
Langmuir. 2007 Aug 28;23(18):9429-34. doi: 10.1021/la701384q. Epub 2007 Aug 3.
A thermoresponsive diblock copolymer, poly(ethyl glycidyl ether)-block-poly(ethylene oxide) (PEGE-b-PEO), is synthesized by successive anionic ring-opening polymerization of ethyl glycidyl ether and ethylene oxide using 2-phenoxyethanol as a starting material, and its solution behavior is elucidated in water. In a dilute 1 wt % solution, the temperature-dependent alteration in the polymer hydrodynamic radius (RH) is measured in the temperature range between 5 and 45 degrees C by pulse-gradient spin-echo NMR and dynamic light scattering. The RH value increased with temperature in two steps, where the first step at 15 degrees C corresponds to the core-shell micelle formation and the second step at 40 degrees C corresponds to the aggregation of the core-shell micelles. The formation of the core-shell micelles is supported by the solubilization of a dye (1,6-diphenyl-1,3,5-hexatriene) in the hydrophobic core, which is recognized for a copolymer solution in the temperature range between 20 and 40 degrees C. In this temperature range, the core-shell micelles and the unimers coexist and the fraction of the former gradually increases with increasing temperature, suggesting equilibrium between the micelles and the unimers. In the concentrated regime (40 wt % solution), the solution forms a gel and the small-angle X-ray scattering measurements reveal the successive formation of hexagonal and lamellar liquid crystal phases with increasing temperature.
以2-苯氧基乙醇为起始原料，通过乙基缩水甘油醚和环氧乙烷的连续阴离子开环聚合反应合成了一种热响应性二嵌段共聚物聚（乙基缩水甘油醚）-嵌段-聚环氧乙烷（PEGE-b-PEO），并阐明了其在水中的溶液行为。在1 wt%的稀溶液中，通过脉冲梯度自旋回波核磁共振和动态光散射在5至45摄氏度的温度范围内测量了聚合物流体力学半径（RH）随温度的变化。RH值随温度分两步增加，其中第一步在15摄氏度时对应核壳胶束的形成，第二步在40摄氏度时对应核壳胶束的聚集。染料（1,6-二苯基-1,3,5-己三烯）在疏水核中的增溶作用支持了核壳胶束的形成，在20至40摄氏度的温度范围内，共聚物溶液中可以观察到这种现象。在此温度范围内，核壳胶束和单聚物共存，且前者的比例随温度升高逐渐增加，表明胶束和单聚物之间存在平衡。在浓溶液体系（40 wt%溶液）中，溶液形成凝胶，小角X射线散射测量结果表明，随着温度升高，依次形成了六方相和层状液晶相。
