Matsuoka Hideki, Maeda Shin'ichi, Kaewsaiha Ploysai, Matsumoto Kozo
Department of Polymer Chemistry, Kyoto University, Kyoto 615-8510, Japan.
Langmuir. 2004 Aug 31;20(18):7412-21. doi: 10.1021/la0492153.
Strongly ionized amphiphilic diblock copolymers of poly(styrene)-b-poly(styrenesulfonate) with various hydrophilic and hydrophobic chain lengths were synthesized by living radical polymerization, and their properties and self-assembling behavior were systematically investigated by surface tension measurement, foam formation, hydrophobic dye solubilization, X-ray reflectivity, dynamic light scattering, small-angle neutron scattering, small-angle X-ray scattering, and atomic force microscope techniques. These copolymer solutions in pure water did not show a decrease of surface tension with increasing polymer concentration. The solutions also did not show foam formation, and no adsorption at the air/water interface was confirmed by reflectivity experiments. However, in 0.5 M NaCl aq solutions polymer adsorption and foam formation were observed. The critical micelle concentration (cmc) was observed by the dye solubilization experiment in both the solutions with and without added salt, and by dynamic light scattering we confirmed the existence of polymer micelles in solution, even though there was no adsorption of polymer molecules at the water surface in the solution without salt. By the small-angle scattering technique, we confirmed that the micelles have a well-defined core-shell structure and their sizes were 100-150 A depending on the hydrophobic and hydrophilic chain length ratio. The micelle size and shape were unaffected by addition of up to 0.5 M salt. The absence of polymer adsorption at the water surface with micelle formation in a bulk solution, which is now known as a universal characteristic for strongly ionized amphiphilic block copolymers, was attributed to the image charge effect at the air/water interface due to the many charges on the hydrophilic segment.
通过活性自由基聚合合成了具有不同亲水和疏水链长度的聚（苯乙烯）-b-聚（苯乙烯磺酸盐）强电离两亲性二嵌段共聚物，并通过表面张力测量、泡沫形成、疏水染料增溶、X射线反射率、动态光散射、小角中子散射、小角X射线散射和原子力显微镜技术系统地研究了它们的性质和自组装行为。这些共聚物在纯水中的溶液并未表现出随着聚合物浓度增加表面张力降低的现象。该溶液也未表现出泡沫形成，并且通过反射率实验证实没有在空气/水界面发生吸附。然而，在0.5M NaCl水溶液中观察到了聚合物吸附和泡沫形成。通过染料增溶实验在加盐和不加盐的溶液中均观察到了临界胶束浓度（cmc），并且通过动态光散射我们证实了溶液中存在聚合物胶束，尽管在无盐溶液中聚合物分子没有在水表面吸附。通过小角散射技术，我们证实了胶束具有明确的核壳结构，并且其尺寸根据疏水和亲水链长度比为100 - 150 Å。胶束的尺寸和形状不受添加高达0.5M盐的影响。在本体溶液中形成胶束时水表面没有聚合物吸附，这现在被认为是强电离两亲性嵌段共聚物的普遍特征，这归因于亲水链段上的许多电荷在空气/水界面处的镜像电荷效应。
