Thermodynamic properties of micellization of Sulfobetaine-type Zwitterionic Gemini Surfactants in aqueous solutions--a free energy perturbation study.

Autor: Liu G; Department of Chemistry, School of Sciences, Harbin Institute of Technology, Harbin, Heilongjiang Province, PR China. liuguoyu1@yahoo.com.cn, Gu D, Liu H, Ding W, Luan H, Lou Y
Jazyk: angličtina
Zdroj: Journal of colloid and interface science [J Colloid Interface Sci] 2012 Jun 01; Vol. 375 (1), pp. 148-53. Date of Electronic Publication: 2012 Feb 28.
DOI: 10.1016/j.jcis.2012.02.027
Abstrakt: In this article, the validity and accuracy of the free energy perturbation (FEP) model used in a previous article for ionic liquid-type Gemini imidazolium surfactants (ILGISs) is further evaluated by using it to model the Enthalpy-entropy compensation of Sulfobetaine-type Zwitterionic Gemini Surfactants (SZGSs), with different carbon atoms of the hydrophobic group or the spacer chain length, in aqueous solutions. In the FEP model, the Gibbs free energy contributions to the driving force for micelle formation are computed using hydration data obtained from molecular dynamics simulations. According to the pseudo-phase separation model, the thermodynamic properties of micellization in aqueous solutions for SZGS were discussed. The results show that the micellization of SZGS in aqueous solutions is a spontaneous and entropy-driven process. It is linearly Enthalpy-entropy compensated and different from the micelle formation of ILGIS but similar to anionic surfactants. The compensation temperature was found to be (302±3)K which was lower than ILGIS. As the temperature rises, the micellization is easy initially but then becomes difficult with the unusual changes of enthalpy values from positive to negative. The contribution of entropy change to the micellization tends to decrease but the contribution of enthalpy change tends to increase. In particular, as the number carbon atoms in the alkyl chains and spacer chains are increased, the thermodynamic favorability and stability of the micelles both increase.
(Crown Copyright © 2012. Published by Elsevier Inc. All rights reserved.)
Databáze: MEDLINE
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