Direct synthesis and stimulus-responsive micellization of Y-shaped hydrophilic block copolymers
Direct synthesis and stimulus-responsive micellization of Y-shaped hydrophilic block copolymers
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DOI：
10.1021/ma0487756
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发表时间：
2004-12-28
期刊：
影响因子：
5.5
通讯作者：
Armes, SP
中科院分区：
文献类型：
--
作者：
Cai, YL;Tang, YQ;Armes, SP
以2个等量的2-羟乙基丙烯酸酯为催化剂，在2个商业单胺包封的聚氧亚烯上加成，然后用过量的2-溴异丁基溴进行酯化反应，合成了两个双官能团原子转移自由基聚合（ATRP）大引发剂。H-1 NMR和MALDI-TOF质谱（MALDI-TOF MS）与两种ATRP宏观引发剂的结构一致。通过ATRP在20℃的甲醇中聚合不同的亲水甲基丙烯酸单体，用这些大引发剂合成了一系列定义明确的y型、ph响应型或热响应型嵌段共聚物。采用H-1 NMR、动态光散射（DLS）和表面张力测定法研究了所选y型嵌段共聚物在水溶液中的刺激响应胶束作用。为了比较，我们还合成了相应的线性二嵌段共聚物，并研究了它们在水溶液中的胶束化性能。DLS研究表明，所选择的y型嵌段共聚物的非线性结构通常导致其形成的胶束尺寸与相应的线性二嵌段共聚物形成的胶束尺寸不同。DLS研究还证实，其中一种新型y形嵌段共聚物在水溶液中表现出“精神分裂症”热响应行为。接近单分散的球形胶束在较高的温度下（高于45℃）得到，而多分散的非球形胶束似乎在较低的温度下（低于12℃）形成。
Two bifunctional atom transfer radical polymerization (ATRP) macroinitiators were synthesized via Michael addition of 2 equivalents of 2-hydroxyethyl acrylate to two commercial monoamine-capped poly(alkylene oxides), Jeffamine XTJ-506 and Jeffamine XTJ-507, followed by esterification using excess 2-bromoisobutyryl bromide. H-1 NMR and MALDI-TOF mass spectra (MALDI-TOF MS) were consistent with the expected structures for these two ATRP macroinitiators. A range of well-defined, Y-shaped, pH-responsive or thermoresponsive block copolymers was synthesized using these macroinitiators by polymerizing various hydrophilic methacrylic monomers via ATRP in methanol at 20 C. The stimulus-responsive micellization of selected Y-shaped block copolymers in aqueous solution was investigated by H-1 NMR, dynamic light scattering (DLS), and surface tensiometry. For comparative purposes, their linear diblock copolymer counterparts were also synthesized, and their micellization properties in aqueous solution were investigated. DLS studies indicated that the nonlinear architectures of selected Y-shaped block copolymers usually resulted in micelles with differing dimensions to those formed by the corresponding linear diblock copolymers. DLS studies also confirmed that one of these new Y-shaped block copolymers exhibited "schizophrenic" thermoresponsive behavior in aqueous solution. Near-monodisperse spherical micelles were obtained at higher temperatures (above 45 degreesC), whereas polydisperse nonspherical micelles appear to be formed at lower temperatures (below 12 degreesC).