INFLUENCE OF ALKYL CHAIN-BRANCHING OF COSURFACTANT ON THE WATER SOLUBILIZING CAPACITY OF A WATER-IN-OIL MICROEMULSION

In this article water solubilization capacities of water-in-oil microemulsions formed from fatty acid soaps and isomers of alcohols as a function of alkyl chain length of the oil and soap have been reported. The water solubilization capacities of soap microemulsions have been compared with the cetyltrimethylammonium bromide and sodium dodecyl sulphate systems. Branching in the cosurfactant chain decreased the water solubilization capacity for all the soaps and detergent microemulsions. However, for the CTAB-pentanol and CTAB-octanol microemulsion systems the water solubilizing capacity was found to increase. The solubilization behaviour is interpreted in terms of the partitioning of the alcohol among the oil, water and interface, depending on the chain length of the oil and surfactant, as well as molecular packing at the interface in relation to the disorder produced due to branching in the cosurfactant chain. The molar ratio of alcohol to soap at the droplet interface was found to increase with the length of the oil chain. © 1990.