LCST可调的温度响应型核交联星型聚合物的合成与相变行为

Synthesis and Phase Transition Behavior of Thermo-Responsive Core Cross-Linked Star Polymers with Tunable LCST

通过“臂优先”的途径和可逆加成-断裂转移(RAFT)自由基聚合合成了以聚(聚乙二醇甲醚丙烯酸酯-co-丙烯酸乙氧基乙氧基乙酯)(P(PEGA-co-DEGA))为线型外臂的温度响应型核交联星型聚合物(CCSP)。采用傅里叶红外光谱(FT-IR)、核磁共振氢谱(1H-NMR)和凝胶渗透色谱(GPC)等手段对合成产物进行了表征,同时以紫外-可见光谱(UV-Vis)对该核交联星型聚合物的相变行为进行了研究。结果表明,所制备的核交联星型聚合物具有可调控的低临界溶解温度(LCST),通过改变外臂温敏单体配比和聚合物溶液的pH,可控制所得CCSP的LCST在49~82℃可调。而且与线型外臂相比,CCSP由于其独特的拓扑结构具有更窄的相转变温度范围和更灵敏的相变过程。

A series of thermo-responsive core cross-linked star polymers(CCSP),in which poly(methoxypolyethylene glycol-co-di(ethylene glycol)ethyl ether acrylate)(P(PEGA-co-DEGA))served as the thermo-responsive arm,have been successfully prepared via reversible addition-fragmentation chain transfer(RAFT)polymerization using the“arm-first”approach.Fourier transform infrared spectroscopy(FT-IR)and nuclear magnetic resonance spectroscopy(1H-NMR)have been applied to characterize the structure and composition of the resultant polymers.The molecular weight of the P(PEGAco-DEGA)arm and the corresponding CCSP were obtained by gel permeation chromatography(GPC)analysis,which showed that the efflux time of CCSP was significantly shortened compared with its corresponding arm,indicating that the CCSP was successfully prepared.The phase transition behavior of the resultant CCSP was evaluated by UV-Vis spectroscopy.Results showed that the low critical solution temperature(LCST)of CCSP displayed a downward trend with increasing the content of DEGA in the P(PEGA-co-DEGA)arm.The LCST of CCSP was also influenced by the pH value of the solution due to the ionization of the carboxylic acid groups at the end of the polymer chains,leading to an upward trend with the increase of pH value.The experimental results indicated that the LCST of CCSP could be controlled in the range of 49-82℃by adjusting the molar ratios of PEGA to DEGA in the arm and the pH value of the solution.Furthermore,the prepared CCSP demonstrated a narrower temperature range of phase transition,thereby resulting in a faster phase separation process in comparison to the corresponding linear arm.