Effect of Chain Length of Alkanes on Water-in-Oil Microemulsions

In the present study, observations and data on the formation and characterization of water-in-oil (W/o) microemulsion systems composed of a cationic surfactant (Cetyltrimethylammoniumbromide)-water-alkanes (C₆-C₇) 2-ethyl-1-hexanol have been reported. The influence of the alkane chain length on the formation of microemulsion systems has been investigated. When the amount of oil or water was increased, the appearance of microemulsion changed from clear to bluish to turbid. These transitions were indentified on the basis of both resistance measurement and visual appearance. Changes in specific resistance with water composition were interpreted in terms of water inforced-micellar structural changes. The critical moles of water/mole of oil ratio, Vc values, at which the microemulsion remains stable, was calculated from viscosity measurements. The linear dependence of Vc values on the number of carbon atoms in the alkyl chain of oil has been reported for predicting the size of the chain length of oil for the formation of a wide range of stable W/o microemulsions. The standard free energy change for transfer of cosurfactant from oil phase to the interfacial phase is also reported.