Stepwise ordering of imidazolium-based cationic surfactants during cooling-induced crystallization.
Stepwise ordering of imidazolium-based cationic surfactants during cooling-induced crystallization.
复制标题
冷却诱导结晶过程中咪唑基阳离子表面活性剂的逐步排序。
作者：
Sun Shufeng;Sun Haiyuan;Luo Junjie;Yu Zhiwu
咪唑阳离子表面活性剂是分子自组装中一类新的结构单元。这些咪唑鎓基阳离子表面活性剂在相变过程中可以表现出各种形态。本文采用等温滴定量热法、差示扫描量热法、同步辐射小角和广角X射线散射、冷冻断裂电子显微镜、光学显微镜、电导率和傅里叶变换红外光谱研究了氯化十六烷基3甲基咪唑（C（16）mimCl）水分散液（0.5-10 wt %）的自组装和相行为。发现C（16）mimCl在水溶液中可形成两种不同的晶相。在较高的C（16）mimCl浓度（> 6wt%）下，初始球形胶束在冷却时直接转化为稳定的结晶相。在较低浓度（0.5或1重量%）下，胶束在冷却时首先转化为亚稳结晶相，然后在低温下进一步温育时转化为稳定结晶相。电导测量表明，两种晶相具有相似的表面电荷密度和表面曲率。此外，两个晶相的显微镜和光谱研究表明，亚稳晶相具有预组装形态和亚分子有序堆积状态，有助于最终稳定的晶体结构。在最终结晶状态之前形成预定结构加深了我们对常见表面活性剂和两亲性离子液体结晶机理的理解，因此应该被广泛认识和探索。
Surfactants bearing imidazolium cations represent a new class of building blocks in molecular self-assembly. These imidazolium-based cationic surfactants can exhibit various morphologies during phase transformations. In this work, we studied the self-assembly and phase behavior of 1-hexadecyl-3-methylimidazolium chloride (C(16)mimCl) aqueous dispersions (0.5-10 wt %) by using isothermal titration calorimetry, differential scanning calorimetry, synchrotron small- and wide-angle X-ray scattering, freeze-fracture electron microscopy, optical microscopy, electrical conductance, and Fourier transform infrared spectroscopy. It was found that C(16)mimCl in aqueous solutions can form two different crystalline phases. At higher C(16)mimCl concentrations (>6 wt %), the initial spherical micelles convert directly to the stable crystalline phase upon cooling. At lower concentrations (0.5 or 1 wt %), the micelles first convert to a metastable crystalline phase upon cooling and then transform to the stable crystalline phase upon further incubation at low temperature. The electrical conductance measurement reveals that the two crystalline phases have similar surface charge densities and surface curvatures. Besides, the microscopic and spectroscopic investigations of the two crystalline phases suggest that the metastable crystalline phase has preassembled morphology and a preordered submolecular packing state that contribute to the final stable crystalline structure. The formation of a preordered structure prior to the final crystalline state deepens our understanding of the crystallization mechanisms of common surfactants and amphiphilic ionic liquids and should thus be widely recognized and explored.
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DOI：
10.1002/cphc.200700508
发表时间：
2007-10
期刊：
Chemphyschem : a European journal of chemical physics and physical chemistry
影响因子：
--
作者：
A. Wulf;K. Fumino;D. Michalik;R. Ludwig
通讯作者：
A. Wulf;K. Fumino;D. Michalik;R. Ludwig
DOI：
10.1021/jp802313c
发表时间：
2008-06
期刊：
The journal of physical chemistry. B
影响因子：
--
作者：
S. Sasaki
通讯作者：
S. Sasaki
影响因子：
5.5
作者：
A. Ghosh;E. Woo;Ya-Sen Sun;Li-Ting Lee;Ming-Chien Wu
通讯作者：
A. Ghosh;E. Woo;Ya-Sen Sun;Li-Ting Lee;Ming-Chien Wu
DOI：
10.1021/jp103293x
发表时间：
2010-08
期刊：
The journal of physical chemistry. B
影响因子：
--
作者：
S. Sasaki
通讯作者：
S. Sasaki
DOI：
10.1021/jp901048q
发表时间：
2009-06
期刊：
The journal of physical chemistry. B
影响因子：
--
作者：
S. Sasaki
通讯作者：
S. Sasaki