A THERMODYNAMIC MODEL OF CLOUDING IN WATER ALCOHOL ETHOXYLATE MIXTURES

An analysis of the clouding phenomenon in water nonionic surfactant systems incorporating the effect of the chemical structure of the nonionic surfactant is made in terms of a Flory-Huggins approach. The lower part of the miscibility curve of the system can be described by introducing a temperature-dependent interaction parameter. From contributions of the various groups in the nonionic surfactant to the interaction parameter, it appears that clouding is the result of the balance between the hydrophobic and hydrophilic interactions of the micelle with its surroundings. Zero-interaction temperatures where attractive and repulsive interactions compensate each other are predicted correctly. It appears that the micellar size can increase as the clouding temperature is approached. The model gives an improved insight into the physiochemical aspects of the nonionic water phase separation, i.e., the clouding phenomenon. © 1992.