Influence of Additive on the Micellar Properties of Nonionic Surfactant

Nonionic surfactants cannot withstand elevated temperature and become perceptible even with naked eye known as "clouding", the temperature at which micellar solution breaks up into two phases is referred as a "Cloud Point" (CP). Addition of foreign substance to the surfactant solution does change the temperature at which clouding phenomenon occurs. It was noted that at 10% surfactant solution, the CP is 66.9 degrees C However initially there is decrease in CP with increased surfactant concentration due to increase in micelle concentration. The phase separation results from micelle-micelle interaction. At high surfactant concentration, the CP continues to increase since at high surfactant concentration there exists structured water-surfactant system. With rise in temperature this structure breaks which favors micelle-micelle interaction. The effect of additive on the CP of surfactant is positive. Considering the cloud point as threshold temperature of the solubility, the thermodynamics of the clouding process has been evaluated using "Phase Separation Model".