具有可控温敏相变行为的四氢呋喃-缩水甘油超支化共聚醚的合成

SYNTHESIS AND CONTROLLED PHASE TRANSITION BEHAVIOR OF THERMOSENSITIVE HYPERBRANCHED POLY(TETRAHYDROFURAN-co-GLYCIDOL)

采用四氢呋喃(THF)和缩水甘油(glycidol)进行阳离子开环共聚,一步合成了主链中含有柔性聚四氢呋喃线型链段的温敏性超支化共聚醚.采用定量13C-NMR确定了共聚醚的超支化结构,同时计算了其支化度.利用体积排除色谱-多角度激光光散射(SEC-MALLS)对聚合物分子量及分布进行了表征.紫外-可见光光谱(UV)测试发现共聚醚水溶液透过率在最低临界溶解温度(LCST)附近呈现剧烈变化,但是其相变速率缓慢,相变平衡时间可达30 min;且聚合物溶液的相变速率和紫外光透过率变化具有温度依赖性.采用透射电镜(TEM)对相变过程观察后发现,这种缓慢相变过程是由于超支化共聚醚组装形成的胶束随温度升高发生不同程度聚集所致.

Backbone-thermosensitive hyperbranched polyethers were synthesized in one step by the cationic ring-opening copolymerization of tetrahydrofuran and glycidol. The hyperbranched polyethers had soft polytetrahydrofuran segments in the backbones, and their structures were characterized by quantitative 13C- NMR. Then the degree of branching and the ratio of glycidol units incorporated into the structure were also calculated. The molecular weight and molecular weight distribution were characterized by size exclusion chomatography-multi-angle laser light scattering （SEC-MALLS）. The thermoresponsive phase transition behavior of the hyperbranched polyether in aqueous solution was intensively investigated by UV-Vis spectrometer equipped with a thermocell. It was found that the UV transmittance of the aqueous solution of the hyperbranched polyethers decreased dramatically when the temperature was increased above LCST, but the balance of phase transition was very slow and the phase transition time was up to 30 min. At the same time, the kinetics of phase transition and final value of UV transmittance were dependent on the temperature, which suggested that the phase transition process could be effectively controlled by adjusting the temperature. TEM inspection showed that the hyperbranched polyethers in aqueous solution could assemble to form micelles at low temperatures. And then, the micelles gradually aggregated as the temperature was increased above LCST, which caused the slow and controlled phase transition process.