Abstract: Short chain fatty alcohol (ethanol, n-propanol, n-butanol) was added into the 1:1 mixed systems of cationic and anionic surfactants (sodium dodecyl sulfate-octyltrimythylammonium bromide, sodium dodecyl sulfate-dodecyltrimythylammonium bromide).The precipitation of this kind of catanionic surfactants will be dissolved, and an aqueous two-phase will be formed after the addition of short-chained fatty alcohol. The surfactant concentration is bigger in the upper phase, and smaller in the lower phase respectively. The results of TEM and birefringence observation showed that vesicle and liquid crystal spontaneously formed in the lower and upper phase, respectively. The volume ratio of the aqueous two-phase would increase with the decrease of carbon chain of alcohol, and decrease with the increase of temperature. Sonication also promotes the transition from precipitation to vesicle, which is similar to the effect of addition of short chain fatty alcohols.

Key words: Catanionic surfactant, Short chain fatty alcohol, Aqueous surfactant two-phase, Vesicle, Phase behavior