Acta Chim. Sinica ›› 2015, Vol. 73 ›› Issue (8): 835-839.DOI: 10.6023/A15030212 Previous Articles     Next Articles



张娜a, 陈国君a, 陈坤a, 李洪光b, 郝京诚a   

  1. a 山东大学化学与化工学院 济南 250100;
    b 中国科学院兰州化学物理研究所清洁能源化学与材料实验室 兰州 730000
  • 投稿日期:2015-03-28 发布日期:2015-07-07
  • 通讯作者: 李洪光
  • 基金资助:

    项目受中科院百人计划(No. Y20245YBR1)和国家自然科学基金(Nos. 21402215, 61474124)资助.

Viscoelastic Emulsions Stabilized by Salt-Free Catanionic Surfactants

Zhang Naa, Chen Guojuna, Chen Kuna, Li Hongguangb, Hao Jingchenga   

  1. a School of Chemistry and Chemical Engineering, Shandong University, Jinan 250100;
    b Laboratory of Clean Energy Chemistry and Materials, Lanzhou Institute of Chemical Physics, Chinese Academy of Sciences, Lanzhou 730000
  • Received:2015-03-28 Published:2015-07-07
  • Supported by:

    Project supported by the Hundred Talents Program of Chinese Academy of Sciences (No. Y20245YBR1) and the National Natural Science Foundation of China (Nos. 21402215, 61474124).

Salt-free cationic/anionic surfactant mixtures (catanionics) have received considerable attention in recent years due to their high surface activity and rich phase behavior. Although there have been extensive reports about their aggregation behavior, rheological properties and interaction with guest molecules in aqueous solutions, investigations in nonaqueous solutions and/or in solvent mixtures are rare. Typically, emulsions have enormous applications both in industry and daily life, and catanionics have long been predicted to be good emulsifiers. However, study in this direction is still in its infancy. Here, by acid-base neutralization we have prepared a catanionic surfactant, tetradecyltrimethyl ammonium laurate (TTAL), which was found to be able to effectively emulsify paraffin oil/water system. The emulsions can be obtained by simple hand-shaking, which is in sharp contrast to many of existing emulsions which can be only obtained through high-energy input. Optical microscopy observations revealed the presence of polydisperse, closely-packed emulsion droplets with diameters ranging from several micrometers to hundreds of micrometers. An increase in the amount of added TTAL at fixed water content induces a decrease of both the averaged size and polydispersity of the droplets. In contrast, the influence of the water content on the averaged size and polydispersity of the droplets is not obvious. Steady-state shear measurements indicated that the emulsions are shear-thinning, presumably due to the destruction of the close-packing of the emulsion droplets under shear. Oscillatory shear measurements revealed that the emulsions are viscoelastic with the elastic modulus higher than the viscous modulus over the whole investigated frequency range. At higher amount of added TTAL, the viscoelasticity of the emulsion also becomes higher and the emulsion begins to exhibit a yield stress. These observations are reminiscent of the characteristics of closely-packed vesicles formed by catanionics in water, and indicate that this unique class of surfactant can be potentially utilized for the construction of new generation of emulsions.

Key words: catanionic surfactant, emulsion, viscoelastic, closely packed