Micellization and gelation of aqueous solutions of star-shaped PLLA-PEO block copolymers
Micellization and gelation of aqueous solutions of star-shaped PLLA-PEO block copolymers
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DOI：
10.1021/ma021639l
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发表时间：
2003-06-03
期刊：
影响因子：
5.5
通讯作者：
Kim, SC
中科院分区：
文献类型：
--
作者：
Park, SY;Han, BR;Kim, SC
无毒且可生物降解的星形聚((L)-丙交酯-b-环氧乙烷)(星形PLLA-PEO)嵌段共聚物是通过两种反应性前体，羟基封端的三臂聚((L)-丙交酯)(星形PLLA)和α-单羧基-omega-单甲氧基聚(环氧乙烷)(CMPEO)的偶联反应合成的。对所得星形嵌段共聚物的化学结构和物理性质进行了表征。在星型嵌段共聚物的稀水溶液中，研究了胶束化行为，在特定浓度和特定温度下，发生了单聚体到胶束的转变。 1,6-二苯基-1,3,5-己三烯(DPH)溶解在胶束核心中，形成胶束时DPH在356 nm处的吸光度增加。此外，有效直径受温度影响很大。随着温度升高，胶束尺寸急剧减小。在高浓度溶液中，星形嵌段共聚物表现出温度敏感的溶胶-凝胶转变行为。超过特定浓度，整个系统不能通过胶束堆积而流动。然而，随着温度升高，由于PEO链脱水和收缩，胶束体积减小，堆积结构被破坏，体系飞散。在倾斜小瓶法得到的溶胶-凝胶转变相图中，随着PLLA嵌段和PEO嵌段分子量的增加，临界凝胶浓度降低，边界曲线左移，凝胶区域扩大。
Nontoxic and biodegradable star-shaped poly((L)-lactide-b-ethylene oxide) (star PLLA-PEO) block copolymers were synthesized by the coupling reaction of two reactive precursors, a hydroxy-terminated 3-armed poly((L)-lactide) (star PLLA) and alpha-monocarboxy-omega-monomethoxypoly(ethylene oxide) (CMPEO). The chemical structure and physical properties of the resulting star-block copolymers were characterized. In the dilute aqueous solutions of star-block copolymers, micellization behavior was investigated, and over specific concentration and specific temperature, the unimer to micelle transition occurred. 1,6-Diphenyl-1,3,5-hexatriene (DPH) was solubilized in the micelle core, and the absorbance of DPH at 356 nm increased when micelle was formed. In addition, the effective diameter was highly affected by temperature. With increasing temperature, micelle size decreased dramatically. In high-concentration solution, star-block copolymer showed temperature-sensitive sol-gel transition behavior. Over specific concentration, the whole system cannot flow by the packing of micelles. However, with increasing temperature, packing structure was destroyed by the decrease of the micelle volume due to the dehydration and contraction of the PEO chain, and the system flew. In the sol-gel transition phase diagram obtained by the vial tilting method, the critical gel concentration decreased, the boundary curve shifted to the left, and the gel regions were expanded with increasing the molecular weight of PLLA block and PEO block.