Abstract: The molecular interaction parameter(βm), molecular exchange energy(εm) and thermodynamic parameters(ΔGom, ΔHom, ΔSom) of mixed micelle for the binary systems of polyoxyethylene(20) sorbitan ester(Tween) and oleylpolyoxyethylene(10)(Brij97) were calculated from surface tension data. The effects of the molecular structure of Tweens, the compositions of the mixed system and the temperature were discussed. For the systems investigated, it has been showed that the synergism and molar fraction of Tween(Xm1) in mixed micelles increase with the increase of carbon chain of Tween. The larger the molar fraction of Tween(α1) is, the greater the free energy(ΔGom) in Tween60/Brij97 mixed surfactants. At α1≤0.33, the mixtures show synergism at mixed micelle formation, while mixtures do not have synergism with α1＞0.33; the critical micelle concentration, free energy and synergism in Tween60/Brij97 mixed micelle decrease as the temperature increase, but the enthalpy and entropy are reverse.

Key words: mixed micelle, interaction parameter (&, beta, m), molecular exchange energy(&, epsilon, m), thermodynamic parameters(&, Delta, Gom,&, Delta, Hom,&, Delta, Som)