Lyotropic liquid crystallinity in amphiphilic block copolymers: Temperature effects on phase behavior and structure for poly(ethylene oxide)-b-poly(propylene oxide)-b-poly(ethylene oxide) copolymers of different composition
Lyotropic liquid crystallinity in amphiphilic block copolymers: Temperature effects on phase behavior and structure for poly(ethylene oxide)-b-poly(propylene oxide)-b-poly(ethylene oxide) copolymers of different composition
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DOI：
10.1021/la951025s
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发表时间：
1996-05-29
期刊：
影响因子：
3.9
通讯作者：
Khan, A
中科院分区：
文献类型：
--
作者：
Alexandridis, P;Zhou, DL;Khan, A
利用h -2核磁共振和小角x射线散射（SAXS）研究了三种不同组成（EO）(6)(PO)(34)(EO)(6)(L62) (EO)(PO)(30)(EO)(13) （PO)（L64)）和（EO）（37）（PO）（58）（EO）（37） （P105））的聚（环氧乙烷）-b-聚（环氧乙烷）-b-聚（环氧乙烷）（PEO-PPO-PEO）共聚物的二元两亲性聚合物-水体系的相行为和结构随聚合物浓度和温度的变化规律。随着聚环氧乙烷含量的增加和聚合物分子量的增加，形成的溶致液晶（LLC）相的数量依次为L62 < L64 < P105。L62只能形成层状LLC相，而P105随着聚合物浓度的增加，能够自组装成（以体为中心紧密堆积的）立方相、六边形相和层状LLC相。加热后，L62-water和L64-water体系的LLC相随水膨胀；在p105 -水系统中没有检测到这种膨胀。LLC区的热稳定性依次为立方<六方<片层和L62 < L64 < P105。温度升高导致L62和L64片层的界面面积减小，周期性增加。在p105 -水体系中，层状和六边形LLC区域的结构尺寸受温度的影响不大。随着聚合物含量的增加，层状周期性和嵌段共聚物界面面积均减小。讨论了影响两亲性共聚物自组装方式的因素，并将PEO-PPO-PEO共聚物与非离子表面活性剂在水中的相行为进行了比较。
The phase behavior and structure of binary amphiphilic polymer-water systems have been studied as a function of polymer concentration and temperature for three poly(ethylene oxide)-b-poly(propylene oxide)-b-poly(ethylene oxide) (PEO-PPO-PEO) copolymers of different composition, (EO)(6)(PO)(34)(EO)(6)(L62),(EO)(13)(PO)(30)(EO)(13) (L64), and (EO)(37)(PO)(58)(EO)(37) (P105), by using H-2-NMR and small-angle X-ray scattering (SAXS). The number of lyotropic liquid crystalline (LLC) phases formed increases with the poly(ethylene oxide) content and the molecular weight of the polymers in the order L62 < L64 < P105. Only a lamellar LLC phase is formed by L62, while P105 is capable of self-assembling with increasing polymer concentration into (body-centered close-packed) cubic, hexagonal, and lamellar LLC phases. Upon heating, the LLC phases of the L62-water and L64-water systems swell with water; no such swelling is detected for the P105-water system. The thermal stability of the LLC regions increases in the order cubic < hexagonal < lamellar and L62 < L64 < P105. An increase of the temperature results in a decrease in the interfacial area and an increase in the periodicity of the L62 and L64 lamellae. In the P105-water system, the structural dimensions in the lamellar and hexagonal LLC regions are not much affected by temperature. Both the lamellar periodicity and the block copolymer interfacial area decrease with increasing polymer content, for all polymers. The factors influencing the self-assembly mode of amphiphilic copolymers are discussed, and the phase behavior of the PEO-PPO-PEO copolymers in water is compared to that of nonionic surfactants.