物理化学学报 >> 2013, Vol. 29 >> Issue (07): 1401-1407.doi: 10.3866/PKU.WHXB201304282

热力学，动力学和结构化学 上一篇    下一篇

表面活性剂分子间弱相互作用的直接能量表征——高灵敏等温滴定量热法

娄朋晓1, 王玉洁2,3, 白光月1, 范朝英1, 王毅琳3   

  1. 1 河南师范大学化学化工学院, 绿色化学介质与反应省部共建教育部重点实验室, 河南 新乡 453007;
    2 河南科技学院化学化工学院, 河南 新乡 453003;
    3 中国科学院化学研究所北京分子科学国家实验室, 胶体界面重点实验室, 北京 100190
  • 收稿日期:2013-02-18 修回日期:2013-04-27 发布日期:2013-06-14
  • 通讯作者: 白光月 E-mail:baiguangyue@htu.cn
  • 基金资助:

    国家自然科学基金(21273061)和北京分子科学国家实验室开放课题基金资助

Direct Evidence for the Energy of Weak Interactions between Surfactant Molecules Using High Sensitivity Isothermal Titration Calorimetry

LOU Peng-Xiao1, WANG Yu-Jie2,3, BAI Guang-Yue1, FAN Chao-Ying1, Wang Yi-Lin3   

  1. 1 Key Laboratory of Green Chemical Media and Reactions, Ministry of Education, School of Chemistry and Engineering, Henan Normal University, Xinxiang 453007, Henan Province, P. R. China;
    2 School of Chemistry and Engineering, Henan Institute of Science and Technology, Xinxiang 453003, Henan Province, P. R. China;
    3 Key Laboratory of Colloid and Interface Science, Beijing National Laboratory for Molecular Sciences (BNLMS), Institute of Chemistry, Chinese Academy of Sciences, Beijing 100190, P. R. China
  • Received:2013-02-18 Revised:2013-04-27 Published:2013-06-14
  • Contact: BAI Guang-Yue E-mail:baiguangyue@htu.cn
  • Supported by:

    The project was supported by the National Natural Science Foundation of China (21273061) and Beijing National Laboratory for Molecular Sciences, China.

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摘要：

分子间弱相互作用热力学研究的直接实验方法就是利用量热手段测定相互作用的能量参数. 本文对TAM III-ITC 纳焦级量热计进行了电标定实验和标准反应热测量, 结果显示本量热计的精密度为±0.09%; 量热用基准物质三羟甲基氨基甲烷(Tris)与盐酸的反应热((-47.48±0.12) kJ·mol-1)与文献值一致. 采用此量热计,对典型的头-尾链型阳离子表面活性剂十二烷基三甲基溴化铵(DTAB)测量得到了与文献报导值很好吻合的临界胶束浓度(cmc)和胶束化焓, 而且对具有亲水-疏水面式刚性结构的生物表面活性剂胆酸钠(NaC)也获得了可靠的结果. 进一步地, 对于相反电荷的混合表面活性剂体系(DTAB/NaC), 分别研究了在富NaC区和富DTAB区体系混合胶束的形成. 结果说明DTAB/NaC混合表面活性剂体系在富NaC区有较强的协同效应, 而在富DTAB区的协同效应较弱. 本文结合电导率测定结果, 对DTAB/NaC混合体系在水溶液中的分子自组装热力学行为进行了有价值的讨论.

关键词: 等温滴定量热, 分子间相互作用, 热力学, 表面活性剂, 相互作用焓, 电导率

Abstract:

Calorimetry is a direct experimental method that can be used to study the thermodynamics of weak interactions between surfactant molecules, allowing the energetic parameters of such interactions to be obtained. In this work, a nano-isothermal titration calorimeter with a thermostat (TAM III) was used to evaluate the thermodynamic behavior of molecular self-assemblies of single and mixed surfactants in aqueous solution. Electrical calibration of this instrument showed that its precision is better than ±0.09%. The accuracy of the system was tested by measuring the reaction heat of tris-hydroxymethylaminomethane (Tris), employed often as a calorimetric standard substance, with hydrochloric acid. The resulting value ((-47.48±0.12) kJ·mol-1) agreed well with that in the literature. We then determined the critical micelle concentration (cmc) and enthalpy of micellization for dodecyltrimethylammonium bromide (DTAB) with a“head-and-tail”structure, which were consistent with reported values, as well as reliable results for sodium cholate (NaC) with a rigid steroid skeleton composed of hydrophilic and hydrophobic surfaces. Furthermore, for the mixed system of oppositely charged surfactants (DTAB/NaC), the mixed cmc and enthalpy of mixed micellization were also obtained in NaC- and DTAB-rich regions. A stronger synergistic effect was observed between the two types of surfactants in the NaC-rich region than in the DTAB-rich one. Conductivity measurements allowed the thermodynamic behavior of the mixed system (DTAB/NaC) to be discussed in detail.

Key words: Isothermal titration calorimetry, Intermolecular interaction, Thermodynamics, Surfactant, Enthalpy of interaction, Conductivity