Acta Phys. -Chim. Sin. ›› 2011, Vol. 27 ›› Issue (01): 11-16.doi: 10.3866/PKU.WHXB20110122


Free Energy Perturbation of Enthalpy-Entropy Compensation for the Micellization of Alkyl Aryl Sulfonates

LIU Guo-Yu1, GU Da-Ming1, LIU Hai-Yan1, DING Wei2, LI Zhong2, CHENG Jie-Cheng3   

  1. 1. Department of Chemistry, School of Sciences, Harbin Institute of Technology, Harbin 150001, P. R. China;
    2. Chemistry and Chemical Engineering College, Daqing Petroleum Institute, Daqing 163318, Heilongjiang Province, P. R. China;
    3. Development Department of Science and Technology, Daqing Oil Field Corp. Ltd., Daqing 163453, Heilongjiang Province, P. R. China
  • Received:2010-10-13 Revised:2010-11-12 Published:2010-12-31
  • Contact: LIU Guo-Yu
  • Supported by:

    The project was supported by the National Key Basic Research Program of China (973) (2005CB221300) and Postgraduate Innovative Science Research Program of Heilongjiang Province, China (YJSCX2008-044HLJ).


We used the free energy perturbation (FEP) method to calculate the solvation free energy according to the mass action model. We did this to investigate the enthalpy-entropy compensation effect of surfactant molecular structures on micellization in solution. The thermodynamic properties of micellization in an aqueous solution for several alkyl aryl sulfonates are discussed. Results show that the solvation free energy calculated from the free energy perturbation is consistent with that from the surface tension method and can be used to discriminate between the capacities of micellization for alkyl aryl sulfonates. The micellization of alkyl aryl sulfonate in an aqueous solution is a spontaneous process and the micellization is enthalpy-entropy compensated. The compensation temperature was found to be (302± 2) K. As the aromatic ring shifts from the edge to the middle of the long carbon chain, the formation ability of the micelle and micelle stability decrease. However, with an increase in the number of carbon atoms on the short or long alkyl chains on the aromatic rings the formation ability and the stability of the micelles increase.

Key words: Alkyl aryl sulfonate, Micelle, Free energy perturbation, Solvation free energy, Enthalpy-entropy compensation