The effect of structure of oil phase, surfactant and co-surfactant on the physicochemical and electrochemical properties of bicontinuous microemulsion.

Efforts were made to prepare bicontinuous microemulsions with ten different oil phases involving aliphatic, linear, and aromatic hydrocarbons as oil phases, two co-surfactants (n-butanol and n-pentanol) and two surfactants: cationic (CTAB) and anionic (SDS). Different weight percentages were employed for the preparation of cationic and anionic surfactant based microemulsions as reported in the literature. Out of the 40 compositions (10 oil phasesx2 co-surfactantsx2 surfactants) thus selected only 28 systems showed stable bicontinuous microemulsion phase. This behavior is explained on the basis of the structures of various constituents present in the microemulsions. Viscosity variations of stable bicontinuous microemulsions are found to depend mainly on the nature of co-surfactant. Conductivity behavior on the other hand depends mainly on the weight percentage and composition of aqueous phase. The solubility of pyrene in the oil phase determines the excimer formation and fluorescence behavior in microemulsions. The electron transfer property of both the water-soluble and the oil-soluble redox systems does not depend on the oil phase and the co-surfactant. The significance and importance of characterizing well defined bicontinuous microemulsions is thus highlighted.