多重响应性超支化星形聚合物的合成与组装以及控制释放研究

Multi-responsive Hyperbranched Star Copolymer: Synthesis, Self-assembly and Controlled Release

含二硫键的自引发单体与2-(2-甲氧基乙氧基)乙基甲基丙烯酸酯(MEO2MA)进行自缩合乙烯基共聚合得到超支化PMEO2MA(H-PMEO2MA).以它作大分子引发剂,引发二甲氨基乙基甲基丙烯酸酯(DMAEMA)进行原子转移自由基聚合,合成了具有温度、pH以及氧化还原多重响应性的超支化星形聚合物H-PMEO2MA-star-PDMAEMA.证明了H-PMEO2MA有低临界溶液温度(LCST);研究了PDMAEMA链段的长度和溶液的pH值对超支化星形聚合物的LCST的影响.当H-PMEO2MA-star-PDMAEMA水溶液温度从2℃升高至室温,H-PMEO2MA变成疏水性而发生聚集,形成以H-PMEO2MA为核,PDMAEMA为壳的胶束.在胶束形成过程中,将尼罗红装载到这种聚合物胶束中,形成释药系统,研究了pH、氧化还原响应性释药性能.

Multi-responsive（temperature,pH and redox） hyperbranched star polymers,poly（2-（2-methoxyethoxy）ethyl methacrylate）-star-poly（dimethylaminoethyl methacrylate）（H-PMEO2MA-star-PDMAEMA） have been successfully synthesized by self-condensing vinyl polymerization of disulfide-based inimer and MEO2MA first,and subsequently atom transfer radical polymerization of DMAEMA with H-PMEO2MA as macroinitiator.The Mn and Mw/Mn of the H-PMEO2MA were 8300 g/mol and 2.61,respectively.H-PMEO2MA-star-PDMAEMAs with different molecular weights were obtained by adjusting the polymerization time.The molecular weight of the hyperbranched star copolymer increased but the polydispersity index（PDI） decreased with increasing polymerization time.Since the PDI of the PDMAEMA formed by ATRP is low,with the molecular weight increase of the PDMAEMA,the relative amount of H-PMEO2MA in the hyperbranched star copolymers becomes less;as a result,the influence of the core H-PMEO2MA’s PDI on the hyperbranched star copolymers decreases.UV/Vis TU-1901 spectrophotometer was used to investigate the lower critical solution temperature（LCST） of the resultant polymer.The LCST of H-PMEO2MA is relatively low（2—10 ℃）.The effects of the compositions and pH of the solution on LCST of the hyperbranched star copolymers were studied.The LCST increased with the chain length increase of PDMAEMA.The pH of the solution has a significant impact on the LCST of the hyperbranched star copolymers.With decrease of the pH value,the protonation degree of PDMAEMA increased,the repulsion between the chain segments enhanced,making the aggregation of the H-PMEO2MA-star-PDMAEMA molecules become difficult,and as a result,the water-solubility of the hyperbranched star copolymers enhanced.In addition,when temperature of the aqueous solution raised from 2 ℃ to room temperature,the spherical micelles with H-PMEO2MA as core and PDMAEMA as shell were formed.During the formation of spherical micelles in the aqueous solution of H-PMEO2MA-star-PDMAEMA and Nile Red,the Nile Red was successfully encapsulated in the micelles.The controlled release of this system,in which Nile Red was used as model drug,was investigated,the results showed that this system is pH and redox-responsive,and may have potential application in drug delivery.