MINIMIZING COSOLVENT REQUIREMENTS FOR MICROEMULSION FORMED WITH BINARY SURFACTANT MIXTURES

Abstract

The role of alcohols in microemulsion formation is primarily two-fold. They function as cosolvents by modifying surfactant partitioning between the aqueous and oleic phases and they function as cosurfactants stabilizing microemulsion to the exclusion of unbounaed structures such as liquid crystals, gels or precipitates. Given the freedom of choice among surfactants and their mixtures, the former role of the alcohol can easily be obviated. However, the latter requirement is more fundamental and not so easily removed. This study provides guidance in the purposeful construction of mixtures of synthetic surfactants which can minimize or eliminate alcohol requirements, depending on temperature and salinity. The approach Involves mixing straight tailed (high solubilization parameter) species with mid-chain branched (low cosolvent requirement) species in a spectrum of mole ratios and identifying the minimum alcohol concentration for stable microemulsion. A number of acceptable systems were found.