Lamellar-to-onion transition with increasing temperature under shear flow in a nonionic surfactant/water system.
Lamellar-to-onion transition with increasing temperature under shear flow in a nonionic surfactant/water system.
复制标题
在非离子表面活性剂/水体系中，剪切流下随着温度升高，层状到洋葱的转变。
DOI：
10.1021/la903251v
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发表时间：
2010
期刊：
影响因子：
--
通讯作者：
T. Kato
中科院分区：
文献类型：
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作者：
Y. Kosaka;Makiko Ito;Y. Kawabata;T. Kato
用小角光散射/剪切应力（Rheo-SALS）和小角X射线散射/剪切应力（Rheo-SAXS）同时测量了C（16）E（7）/D（2）O体系的层状相。当温度升高并在恒定剪切速率（1和3 s（-1））下超过67摄氏度时，剪切应力突然增加，并在去极化SALS中观察到四瓣图案。这些结果表明，层状洋葱转变发生与温度升高，这还没有被报道。洋葱的直径从3 s（-1）的去极化SALS模式获得随温度的升高而增加。这种转变随温度的变化而可逆。流变SALS测量也已在恒温下的剪切速率的逐步增加。SAXS谱图在3s（-1）处的变化表明，随着温度从67 ℃升高到69 ℃，层状晶体的取向变得各向同性，这也支持了层状晶体向洋葱状晶体的转变。在恒定剪切速率（3 s（-1））下，转变温度随表面活性剂浓度的略微增加而迅速增加。从这一点，在我们以前的研究中，在休息的SAXS结果一起，我们推断，在水层厚度的增加是必要的，随着温度的升高，层状洋葱过渡。
Simultaneous measurements of small-angle light scattering/shear stress (Rheo-SALS) and small-angle X-ray scattering/shear stress (Rheo-SAXS) have been performed in the lamellar phase of the C(16)E(7)/D(2)O system. As the temperature is increased and exceeds 67 degrees C at constant shear rates (at 1 and 3 s(-1)), the shear stress increases abruptly and a four-lobe pattern is observed in the depolarized SALS. These results suggest that the lamellar-to-onion transition occurs with increasing temperature, which has not yet been reported. The diameter of onions obtained from the depolarized SALS pattern at 3 s(-1) increases with increasing temperature. The transition is reversible against the change in temperature. The Rheo-SALS measurements have also been made with a stepwise increase in shear rate at constant temperature. The results are consistent with the above temperature-scan experiments at constant shear rate, suggesting that the transition does not depend on the path. The variation of the SAXS pattern at 3 s(-1) indicates that the orientation of lamellae becomes isotropic as the temperature is increased from 67 to 69 degrees C, which also supports the lamellar-to-onion transition. The transition temperature at constant shear rate (at 3 s(-1)) increases rapidly with a slight increase in surfactant concentration. From this, together with the SAXS results at rest in our previous study, we deduce that an increase in the water-layer thickness is necessary for the lamellar-to-onion transition with increasing temperature.