反应性H形嵌段共聚物的合成和自组装

以2,2′-(α-溴异丁酰氧基甲基)丙酰氯与Mn分别为4000和2×104的双端羟基聚乙二醇(PEG)进行酯化反应,制得了含4个端溴的PEG大分子引发剂.它在溴化亚铜/2,2′-联吡啶的存在下,在甲醇中,引发甲基丙烯酸3-三甲氧基硅丙酯(TMSPMA)单体进行原子转移自由基聚合(ATRP),得到两个不同分子量的H形嵌段共聚物Sam 1和Sam 2.其结构和分子量及分布用核磁共振氢谱及GPC表征.用TEM研究它们在N,N-二甲基甲酰胺和水混合溶剂中的自组装行为.组成为(EG)91-b-(TMSPMA)92的Sam 1生成复合囊泡;组成为(EG)455-b-(TMSPMA)176的Sam 2形成大的囊泡聚集体.

SYNTHESIS AND SELF-ASSEMBLY OF REACTIVE H-SHAPED BLOCK COPOLYMERS

The H-shaped block copolymers(PTMSPMA)_2PEG(PTMSPMA)_2 with two compositions,(EG)_91-b-(TMSPMA)_92 and(EG)_455-b-(TMSPMA)_176 have been successively synthesized by atom transfer radical polymerization(ATRP)of tri(methoxylsilyl)propyl methacrylate(TMSPMA)at room temperature in methanol,and the initiation system applied in this system was composed of the 2,2′-(α-bromoisobutyryloxymethyl)propionyl terminated poly(ethylene glycol)(Br_2PEGBr_2)with M_n=4000 or 2×104,CuBr and 2,2′-bipyridine.The four functional macroinitiator,Br_2PEGBr_2 was prepared by reaction of two hydroxyl groups terminated PEG with 2,2′-(α-bromoisobutyryloxymethyl)propionyl chloride.The NMR spectroscopy and GPC measurements were used to characterize the structure and molecular weight and molecular weight distribution of the resultant copolymers.When the H-shaped block copolymers Sam 1 and Sam 2 were self-assembled in DMF and water solvents,and successively condensation reaction of trimethoxysilyl groups in PTMSPMA was carried out,stable large-compound vesicles with 10 nm diameter of pores were formed for Sam 1,but self-assembling of the Sam 2 in the selective solvents produced big vesicles aggregates.These two different morphologies of aggregates are attributed to their relative chain length of water soluble PEG.The vesicles formed from Sam1 with short PEG chains had big surface energy,which will lead them to self-assemble further,forming large-compound vesicles.