Thermodynamical investigations on phase transitions of surfactant-water systems: thermodynamic stability of gel and coagel phases and the role of water molecules in their appearance
Thermodynamical investigations on phase transitions of surfactant-water systems: thermodynamic stability of gel and coagel phases and the role of water molecules in their appearance
复制标题
表面活性剂-水体系相变的热力学研究：凝胶和凝聚凝胶相的热力学稳定性以及水分子在其外观中的作用
DOI：
10.1016/0001-8686(91)80019-g
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发表时间：
1991
影响因子：
15.6
通讯作者：
S. Seki
中科院分区：
文献类型：
--
作者：
M. Kodama;S. Seki
利用差示扫描量热法和自制的高精度绝热量热仪，系统地研究了水和同系长烃链三甲基卤化铵二元体系的凝聚胶、凝胶、液晶和胶束溶液的相行为，几乎涵盖了水含量高达99.9 g%的所有浓度。获得的主要发现总结如下：（i）Tc转变曲线随着含水量的增加呈阶梯式快速下降，特别是在低含水量区域； (ii)具有不同反离子(即氯离子、溴离子和碘离子)的十八烷基三甲基卤化铵的三个二元体系的凝胶相分别以稳定、亚稳定和不稳定状态存在； (iii) 根据这种差异，这三个系统的相变模式也不同； (iv)与(iii)相关，热力学稳定的凝胶相仅通过临界量的水的存在来实现，并且在该凝胶相中观察到结构水，即中间水； (v)从凝聚凝胶到胶束溶液转变的临界现象出现在所谓的克拉夫特点区域。这些发现将基于与赝晶格和水合焓相关的能量循环以及吉布斯能量与温度的关系，从热力学角度进行讨论。
Phase behaviors of coagel, gel, liquid crystal and micellar solutions of binary systems of water and a homologous series of long hydrocarbon-chain trimethylammonium halides, covering almost all concentrations up to 99.9 g% water, were systematically investigated by using differential scanning calorimetry and also a home-made, high precision adiabatic calorimeter. The main findings obtained are summarized as follows: (i)Tctransition curves decrease rapidly in a stepwise way with increasing water content, particularly in the low water content region; (ii) the gel phases of three binary systems ofoctadecyltrimethylammonium halides with different counter-ions, i.e., chloride, bromide and iodide, exist in stable, metastable and unstable states, respectively; (iii) in accordance with this difference, the mode of phase transition also differs among these three systems; (iv) in connection with (iii), the thermodynamically stable gel phase is realized only by the existence of a critical amount of water, and the structural water, i.e., intermediate water, is observed in this gel phase; and (v) the critical phenomenon of the transition from the coagel to micellar solution appears in the so-called Krafft point region.These findings will be discussed from the thermodynamic viewpoint on the basis of the energy cycle associated with pseudo-lattice and hydration enthalpies and also from the Gibbs energy versus temperature relationship.