Department of Natural Sciences, University of Houston-Downtown, One Main Street, Houston, TX 77002-1001, USA.
J Colloid Interface Sci. 2013 Dec 1;411:61-8. doi: 10.1016/j.jcis.2013.08.045. Epub 2013 Sep 8.
Properties of catanionic surfactants can be tailored by the choice of appropriate headgroups and hydrocarbon tails. Thermal behavior of catanionic surfactants can be influenced by the length and number of alkyl chains.
A series of eight catanionic surfactants were synthesized from quaternary ammonium surfactants as the cationic counterpart and bis(2-ethylhexyl)sulfosuccinate (AOT) as the anionic counterpart. The thermal properties and the liquid crystalline properties of these catanionic surfactants were studied by the following methods: Thermal Gravimetric Analysis (TGA), Differential Scanning Calorimetry (DSC), Hot-Stage Polarized Light Microscopy (HSPLM), and X-ray Diffraction (XRD).
The results indicate that transition temperatures, enthalpies of transition, and mesophase structures vary with the length and number of chains attached to the quaternary nitrogen. These compounds exhibit room temperature liquid crystalline (LC) textures that are predominantly "fan-like," as observed by HSPLM, and phases that are hexagonal columnar, as observed by XRD, with the exception of one compound which exists as a nematic liquid crystal at 25°C. Additionally, all of the surfactants also exhibit thermal stability in the range of 256-300°C.
通过选择合适的头基和烃尾，可以调整两性离子表面活性剂的性质。两性离子表面活性剂的热行为可以受到烷基链的长度和数量的影响。
从季铵盐表面活性剂作为阳离子部分和双（2-乙基己基）磺基琥珀酸钠（AOT）作为阴离子部分合成了一系列八种两性离子表面活性剂。通过以下方法研究了这些两性离子表面活性剂的热性质和液晶性质：热重分析（TGA）、差示扫描量热法（DSC）、热台偏光显微镜（HSPLM）和 X 射线衍射（XRD）。
结果表明，过渡温度、过渡焓和中间相结构随连接到季氮原子的链的长度和数量而变化。这些化合物表现出室温液晶（LC）织构，主要是 HSPLM 观察到的“扇形”，以及 XRD 观察到的六方柱状相，除了一种化合物在 25°C 下存在向列液晶相。此外，所有表面活性剂在 256-300°C 的范围内也表现出热稳定性。
