Macroscopic, mesostructured cationic surfactant/neutral polymer films: structure and cross-linking.
Macroscopic, mesostructured cationic surfactant/neutral polymer films: structure and cross-linking.
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宏观介观结构阳离子表面活性剂/中性聚合物薄膜：结构和交联。
DOI：
10.1021/la063004b
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发表时间：
2007
期刊：
影响因子：
--
通讯作者：
K. Edler
中科院分区：
文献类型：
--
作者：
B. M. O'driscoll;C. Fernández;R. Wilson;Jessica Knott;S. Roser;K. Edler
烷基三甲基溴化铵或十六烷基溴化吡啶和聚乙烯亚胺，自发自组装在空气/水界面的介观结构的薄膜已被检查使用一系列的表面敏感技术。这些薄膜是不寻常的，因为它们可以是微米厚，并且相对坚固。在这里，我们表明，膜可以交联，从而从液体表面上除去，它们形成固体，介观结构的聚合物-表面活性剂膜。交联引起的膜的结构变化不大，但冻结在亚稳态介观结构，提高了这些膜的未来应用的潜力。从溶液表面移除后干燥的交联膜在膜内保留有序的纳米级结构。我们还报告了掠入射X射线衍射（GID），这表明大多数膜显示散射一致的二维六方相微晶棒状表面活性剂胶束包裹在聚合物中。聚合物支化对膜结构的影响不大;然而，聚合物分子量具有显著影响。具有较低聚合物MW的膜通常较薄且更有序，而较高聚合物MW的膜较厚且较不有序。增加的pH值导致形成较厚的膜，并提高低分子量膜的有序性，而高分子量膜失去秩序。为了使这些结果合理化，我们提出了一个模型的膜形成过程中，相分离和中间相秩序的动力学和热力学限制所观察到的结构。
Mesostructured films of alkyltrimethylammonium bromides or cetylpyridinium bromide and polyethylenimines that spontaneously self-assemble at the air/water interface have been examined using a range of surface sensitive techniques. These films are unusual in that they can be micrometers thick and are relatively robust. Here we show that the films can be cross-linked and thus removed from the liquid surface where they form, as solid, mesostructured polymer-surfactant membranes. Cross-linking causes little change in the structure of the films but freezes in the metastable mesostructures, enhancing the potential of these films for future applications. Cross-linked films, dried after removal from the solution surface, retain the ordered nanoscale structure within the film. We also report grazing incidence X-ray diffraction (GID), which shows that most films display scattering consistent with 2D-hexagonal phase crystallites of rodlike surfactant micelles encased in polymer. Polymer branching makes little difference to the film structures; however, polymer molecular weight has a significant effect. Films with lower polymer MW are generally thinner and more ordered, while higher polymer MW films were thicker and less ordered. Increased pH causes formation of thicker films and improves the ordering in low MW films, while high MW films lose order. To rationalize these results, we propose a model for the film formation process that relates the kinetic and thermodynamic limits of phase separation and mesophase ordering to the structures observed.