alpha(s)-Casein-PE6400 Mixtures: Thermodynamics of Micelle Formation

作者：Kessler Anne; Weiss Jochen; Stubenrauch Cosima^*

来源：Tenside Surfactants Detergents, 2015, 52(5): 351-361.

DOI：10.3139/113.110385

• alpha(s)-Casein
• blockcopolymers
• PE6400
• isothermal titration calorimetry
• ITC
• aggregate formation
• thermodynamics

Micelles are increasingly used as carrier systems. In previous studies, we have shown that the blockcopolymers PEO13-PPO30-PEO13 and alpha(s)-casein form micelles at distinct temperature and concentration ranges. The aim of the study at hand was to determine the thermodynamics of this micelle formation by isothermal titration calorimetry (ITC). For alpha(s)-casein, micelle formation was investigated as a function of temperature from 15-30 degrees C at pH = 6.6, while micelle formation of PE6400 and of mixtures of PE6400 with alpha(s)-casein was studied from 29-31 degrees C. In addition, the influence of increasing alpha(s)-casein mole fraction from 0.135 x 10(-3) to 3.6 x 10(-3) was examined at 30 degrees C. In case of alpha(s)-casein, the standard experimental approach could be used while we developed a new experimental approach for PE6400 and for the mixture. The results show that the enthalpy of demicellization increases for alpha(s)-casein and decreases for PE6400 with increasing temperature. In case of the mixtures, the enthalpy of demicellization was not influenced by either the temperature or the alpha(s)-casein mole fraction. The results obtained for alpha(s)-casein suggest that the micellization follows a "shell-model". In the case of the mixtures, alpha(s)-casein is likely to form the core of the micelle while the outer part appears to be composed of PE6400. The mixing properties were antagonistic, which was shown by comparing the enthalpies of PE6400 with those of the mixtures. The results show that ITC is a powerful tool to precisely determine micellization properties not only of the single but also of mixed surfactant systems.

• 出版日期2015-9