两亲性含糖三嵌段共聚物的合成与自组装研究

以二(2-溴异丁酸)4,4′-联苯酯(BiBBP)为引发剂,采用顺序加料的方法,用原子转移自由基聚合法(ATRP)合成了一系列窄分子量分布的甲基丙烯酸甲酯(MMA)和6-O-甲基丙烯酰基-1,2;3,4-双-O-亚异丙基-α-D-吡喃半乳糖苷(MAIPGal)的三嵌段共聚物.用GPC和1H-NMR表征了聚合物的相对分子量和链段组成.结果表明,通过改变投料顺序可以合成ABA和BAB型2种三嵌段共聚物,改变投料比和控制单体的转化率可以调控聚合物的链段组成.聚合物脱保护后得到两亲性含糖共聚物.用TEM考察了聚合物在水溶液中的自组装行为,表明具有不同链段组成的共聚物可以形成不同形态的聚集体,含糖段组成高的聚合物易于形成大尺寸的胶团,含糖段组成低的聚合物易于形成结构清晰的囊泡、胶束,其中,含糖段在两边的BAB型共聚物易于形成囊泡,含糖段在中央的ABA型共聚物易于形成胶束.

SYNTHESIS AND SELF-ASSEMBLY OF AMPHIPHILIC TRI-BLOCK COPOLYMERS-CONTAINING GLYCOPOLYMER SEGMENTS

A series of tri-block copolymers of methyl methacrylate (MMA) and 6-O-methacryloyl-1,2;3,4-di-O-isopropylidene-D-galactopyranose ( MAIPGal ) were synthesized by sequential atom transfer radical polymerization (ATRP) of MMA and MAIPGal,using 4,4'-biphenol di(2-bromoisobutyrate) (BiBBP) as the initiator. The chemical composition and molecular weights of the copolymers were characterized by 1H-NMR and GPC. It was demonstrated that the block chain length of both PMMA and PMAIPGal can be tuned by the feed molar ratio and monomer conversion. After de-protecting the isopropylidene groups of PMAIPGal,amphiphilic tri-block copolymers were obtained. Their self-assembly behavior in water was investigated by TEM. We investigated the effects of polymer structure,composition and initial concentration in good solvents on the final morphologies of the aggregates. For BAB copolymers,with the hydrophobic PMMA in the center,when the hydrophilic PGA was short,they tended to form vesicle like assemblies at lower polymer concentration. Increasing the chain length of the PGA chain,large irregular micelles were obtained. For ABA copolymers,small sized micelles were the main morphologies,but they were connected with each other due to the interaction of the PGA segments. The difference of self-assembly behavior was attributed to the polymer structure,which dominates the molecular packing as well as the chain segregation of the glycopolymer chains.