Phase behavior of amphiphilic block copolymers in water-oil mixtures: The pluronic 25R4-water-p-xylene system
Phase behavior of amphiphilic block copolymers in water-oil mixtures: The pluronic 25R4-water-p-xylene system
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DOI：
10.1021/jp951626s
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发表时间：
1996-01-04
影响因子：
--
通讯作者：
Lindman, B
中科院分区：
文献类型：
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作者：
Alexandridis, P;Olsson, U;Lindman, B
在 25°C 下，在由水、对二甲苯和 Pluronic 25R4（一种环氧乙烷两亲性嵌段共聚物）组成的三元体系中观察到具有层状、正六方、反六方和双连续立方液晶区域以及富水 (L(1)) 和富油 (L(2)) 溶液的丰富相行为 (EO)和环氧丙烷(PO)，结构为(PO)(19)(EO)(33)(PO)(19)。使用 1H-NMR 和偏振光检查来识别相界。采用小角X射线散射来确定所形成的各种液晶相的结构并确定所涉及的特征长度。当聚合物重量分数恒定为 0.5 时，用油代替水时，观察到 L(1)、正六方相、层状、反六方相和 L(2) 相的顺序。非极性组分（PPO + 油）的体积分数可以被确定为控制相行为的主要参数。 PPO-PEO-PPO 共聚物的三元相行为与分子量与 25R4 相当的相反嵌段序列 PEO-PPO-PEO 共聚物 (Pluronic L64) 相似。
A rich phase behavior with lamellar, normal hexagonal, reverse hexagonal, and bicontinuous cubic liquid crystalline regions, as well as water-rich (L(1)) and oil-rich (L(2)) solutions, was observed at 25 degrees C in a ternary system composed of water, p-xylene, and Pluronic 25R4, an amphiphilic block copolymer of ethylene oxide (EO) and propylene oxide (PO) with the structure (PO)(19)(EO)(33)(PO)(19). The phase boundaries were identified using ?H-NMR and inspection under polarized light. Small angle X-ray scattering was employed to ascertain the structure of the various Liquid crystalline phases formed and to determine the characteristic lengths involved. The sequence of L(1), normal hexagonal, lamellar, reverse hexagonal, and L(2) phases was observed when replacing water by oil at a constant polymer weight fraction of 0.5. The volume fraction of the apolar components (PPO + oil) can be identified as the major parameter governing the phase behavior. The ternary phase behavior of the PPO-PEO-PPO copolymer is similar to that of the opposite block sequence PEO-PPO-PEO copolymer (Pluronic L64) of comparable molecular weight to 25R4.