Polymer terminal group effects on properties of thermoresponsive polymeric micelles with controlled outer-shell chain lengths
Polymer terminal group effects on properties of thermoresponsive polymeric micelles with controlled outer-shell chain lengths
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DOI：
10.1021/bm050232w
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发表时间：
2005-07-01
影响因子：
6.2
通讯作者：
Okano, T
中科院分区：
文献类型：
--
作者：
Nakayama, M;Okano, T
采用可控活性自由基聚合的方法，合成了具有良好定义的两亲性二嵌段共聚物，该共聚物由热敏性聚合物段聚异丙基丙烯酰胺-co- n， n -二甲基丙烯酰胺（PID）和疏水性聚合物段聚甲基丙烯酸苄酯（PBzMA）组成。PID末端衍生为羟基或苯基是通过偶联剂与末端二硫苯甲酸基裂解暴露的巯基反应实现的。双嵌段共聚物形成具有热响应外壳的核壳型聚合物胶束。流体动力学胶束直径范围从12到31纳米，由不同的PID链长度控制。PID末端组的差异不影响临界胶束浓度或胶束直径。然而，这些基团对胶束热反应有显著的影响。羟基化的PID/PBzMA胶束表现出大约40℃的相变，与PID分子量无关。尽管除了末端基团外，PID链的分子量和组成都是相等的，但具有最外层苯基的胶束表现出明显较低的相变温移，特别是对于具有低分子量PID链的胶束。
Well-defined amphiphilic diblock copolymers comprising thermoresponsive polymer segments of poly(Nisopropylacrylamide-co-N,N-dimethylacrylamide) (PID) and hydrophobic polymer segments, poly(benzyl methacrylate) (PBzMA), were synthesized by controlled living radical polymerization. Terminal derivatization of PID segments to either hydroxyl or phenyl groups was achieved through reactions of coupling agents with thiol groups exposed by cleavage of terminal dithiobenzoate groups. Diblock copolymers formed coreshell type polymeric micelles with thermoresponsive outer shells. Hydrodynamic micellar diameters ranged from 12 to 31 nm, controlled by varying PID chain lengths. Differences in PID terminal groups did not affect the critical micelle concentration or micellar diameters. However, these groups demonstrated a significant influence on the micellar thermoresponses. Hydroxylated PID/PBzMA micelles exhibited a phase transition of approximately 40 degrees C, independent of PID molecular weights. Even though molecular weights and compositions of PID chains were equivalent except for terminal groups, micelles having the outermost surface phenyl groups exhibited drastically lower phase transition temperature shifts, especially for micelles with low molecular weight PID chains.