ON THE ROLE OF SOLVATION FORCES IN COLLOIDAL PHASE-TRANSITIONS

Phase transitions in colloidal systems characterized by increasing col loidal order with increasing temperature have been labeled entropy dri ven. Some colloidal phase transitions that may be identified as entrop y driven are the swelling of clays, the crystallization of proteins, a nd the dehydration of silicotungstate crystals. None of these transiti ons can be understood within the framework of classical colloidal forc e (DLVO) theory. We present a new theoretical treatment of the colloid al force problem that describes the statistical mechanics of colloidal forces through a surface approach. A phase diagram that reproduces ke y features of entropy driven transitions is calculated considering onl y short-range colloidal forces in a system of parallel plate colloids and simple fluid. The role of entropy is further considered by quantif ying transitions with Clapeyron equations.