PHASE TRANSITIONS IN COLLOIDAL SYSTEMS PART II CALORIMETRIC STUDY OF THE PHASE CHANGES IN BINARY OR TERNARY SYSTEM OF WATER, SDS AND PENTANOL

The phase transitions of micellar systems have been studied by Differential Scanning Calorimetry. The binary systems water+pentanol-1, water+SDS or SDS+pentanol-1 and the ternary system water+SDS+pentanol-1 have been investigated. In the monophasic region of the ternary system, two experimental paths have been chosen: the first one describes the influence of the addition of water and the second one describes the influence of the alcohol. The analysis of both cooling or heating thermograms has given indications about the structure of these media. It has been particularly shown that the water can be in two states either in a classical macroscopic form melting at 0°C or enclosed in micelles with a so small dimension that melting of the ice occurs at a lower temperature . So, it has been possible to locate the range of concentration where these two "ices" appear. At the lowest temperature we observe the transformations of pentanol-1. Generally the undercooling is smaller than for other aqueous solutions [1] suggesting an heterogeneous nucleation. The heating experiments suggest that the phase equilibria concern ice (or crystallized pentanol-1) and the solutions of monomers which rapidly are at the critical micelle concentration (CMC).