Thermotropic organization of hydrogen-bond-bridged bolaform amphiphiles.
Thermotropic organization of hydrogen-bond-bridged bolaform amphiphiles.
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DOI：
10.1021/la2000574
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发表时间：
2011-03
期刊：
影响因子：
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通讯作者：
Jing Zhang;Mingjun Zhou;Shan Wang;Jessica R Carr;Wen Li;Lixin Wu
中科院分区：
文献类型：
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作者：
Jing Zhang;Mingjun Zhou;Shan Wang;Jessica R Carr;Wen Li;Lixin Wu
设计合成了一系列含羧酸基季铵盐两亲分子(A-n)。傅立叶变换红外光谱(FT-IR)和变温傅立叶变换红外光谱(FT-IR)表明，通过分子间氢键使羧酸基团二聚，可以构建支化的波拉状结构。用差示扫描量热法、偏光显微镜和X-射线衍射仪表征了支链状二聚铵配合物的热致结构。我们考察了阳离子基团和苯环之间的间隔基对热致有机化的影响。具有较短侧链的A-6在室温下形成简单的层状结构，在145℃以上出现近晶A相，而具有中间侧链长度的A-8在较宽的温度范围内形成近晶A相。随着侧链长度的进一步增加(n=10，12)，形成了具有平面层状周期性的层状结构，这在离子化合物的组织结构中是罕见的。在X射线衍射实验数据的基础上，提出了准二维片层的堆积模型。值得注意的是，随着温度的升高，准2D片层结构可以演变为简单的层结构。结果表明，支化结构可用于调节离子两亲分子的自组装行为，并可用于构建新的层状超结构。
A series of quaternary ammonium amphiphiles (A-n) bearing carboxylic acid groups were designed and synthesized. The branched bolaform structures can be constructed by dimerizations of carboxylic acid groups through intermolecular hydrogen bonding, as demonstrated by the Fourier transform infrared (FT-IR) spectra and the temperature-dependent FT-IR spectra. The thermotropic organizations of branched bolaform ammonium dimer complexes were characterized by differential scanning calorimetry, polarized optical microscopy, and X-ray diffraction. We investigated the influence of the spacer between the cationic group and the benzene ring on the thermotropic organization. A-6 with short lateral alkyl chains formed a simple layered structure at room temperature and exhibited smectic A mesophase above 145 °C, whereas A-8 with intermediate lateral chain length organized into smectic A phase over a wide temperature range. A further increase of the length (n = 10, 12) of the lateral chains resulted in the formation of lamellar structure with in-plane layered periodicity, which is rare in the organization of ionic compounds. A packing model of the quasi-2D lamellar was proposed on the basis of the experimental data of X-ray diffraction results. Notably, the quasi-2D lamellar structure could evolve into a simple layer with the increase of temperature. The present results showed a direct relationship in which the branched architecture can be applied to tune the self-assembly behavior of ionic amphiphiles and is allowed to construct new layered superstructure.