Condensation of self-assembled lyotropic chromonic liquid crystal sunset yellow in aqueous solutions crowded with polyethylene glycol and doped with salt.
Condensation of self-assembled lyotropic chromonic liquid crystal sunset yellow in aqueous solutions crowded with polyethylene glycol and doped with salt.
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DOI：
10.1021/la200505y
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发表时间：
2011-03
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通讯作者：
Heung‐Shik Park;Shin-Woong Kang;L. Tortora;Satyendra Kumar;O. Lavrentovich
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作者：
Heung‐Shik Park;Shin-Woong Kang;L. Tortora;Satyendra Kumar;O. Lavrentovich
我们使用光学和荧光显微镜，密度计，低温透射电子显微镜（cryo-TEM），光谱学，和同步辐射X射线散射研究的相行为的可逆自组装有色聚集体的阴离子染料日落黄（SSY）在水溶液中拥挤的电中性聚合物聚乙二醇（PEG）和掺杂的盐NaCl。PEG使各向同性SSY溶液凝聚成具有高浓度SSY聚集体的液晶区域，与富含PEG的各向同性（I）区域共存。加入到均相N相的PEG导致分离成共存的N和I结构域; N结构域中的SSY浓度高于无PEG的N相的初始浓度。最后，将PEG添加到高度浓缩的均匀N相中导致分离成共存的柱状六方（C）相和I相。这种行为可以定性地解释的耗尽（排除体积）的影响，在两个不同的水平上的作用：在从单体和短聚集体的聚集体组装的水平，并在interaggregate包装的水平。我们还显示了强烈的影响，一价盐NaCl的相图是不同的高浓度和低浓度的SSY。当加入盐时，SSY的稀I溶液显示出凝聚的N畴的外观，但是高度浓缩的C相转变为I和N畴共存。我们认为，盐诱导的电荷在有色聚集体表面的屏蔽导致了两种不同的效应：（a）聚集体的断裂能和轮廓长度增加;（B）SSY聚集体的持久长度减小。
We use optical and fluorescence microscopy, densitometry, cryo-transmission electron microscopy (cryo-TEM), spectroscopy, and synchrotron X-ray scattering to study the phase behavior of the reversible self-assembled chromonic aggregates of an anionic dye Sunset Yellow (SSY) in aqueous solutions crowded with an electrically neutral polymer polyethylene glycol (PEG) and doped with the salt NaCl. PEG causes the isotropic SSY solutions to condense into a liquid-crystalline region with a high concentration of SSY aggregates, coexisting with a PEG-rich isotropic (I) region. PEG added to the homogeneous nematic (N) phase causes separation into the coexisting N and I domains; the SSY concentration in the N domains is higher than the original concentration of PEG-free N phase. Finally, addition of PEG to the highly concentrated homogeneous N phase causes separation into the coexisting columnar hexagonal (C) phase and I phase. This behavior can be qualitatively explained by the depletion (excluded volume) effects that act at two different levels: at the level of aggregate assembly from monomers and short aggregates and at the level of interaggregate packing. We also show a strong effect of a monovalent salt NaCl on phase diagrams that is different for high and low concentrations of SSY. Upon the addition of salt, dilute I solutions of SSY show appearance of the condensed N domains, but the highly concentrated C phase transforms into a coexisting I and N domains. We suggest that the salt-induced screening of electric charges at the surface of chromonic aggregates leads to two different effects: (a) increase of the scission energy and the contour length of aggregates and (b) decrease of the persistence length of SSY aggregates.