Effect of Co-surfactant on Phase Behavior of Microemulsions

OBJECTIVE To study the effect of the type and characterization of co-surfactant on the phase behavior of the microemulsions.METHODS The pseudo-ternary phase diagrams were constructed by the water titration method, and the effect of the co-surfactant on the phase diagram was also investigated. The region of microemulsion and the maximum oil-loaded content were used as the evaluating index. RESULTS The regions of the oil-in-water (o/w) microemulsion of the systems with short-chain alcohol (2-3 C chains) as the co-surfactant are much larger than those with long-chain alcohol (5 C chains). Both n-butanol and phenylmethanol were suitable for preparing microemulsions owing to their CLog P ( near 1) although their carbon chains are longer. The amides with the weak alkalinity can facilitate the forming of the microemulsions using oleic acid as the oil phase. CONCLUSION A better co-surfactant should have the appropriate partition coefficient between oil and water,which may facilitate the forming of the microemulsions.