Wetting nonwetting behaviors in a ternary amphiphilic system

We consider the three-liquid-phase, alpha, beta, and gamma, coexisting system water+n-tetradecane+diethylene glycol monohexyl ether and the densities of these three phases are in the order rho(alpha)<rho(beta)<rho(gamma). An enhanced video pendant drop tensiometer is applied to measure the interfacial tensions to further reconfirm that a wetting transition occurs by the gamma phase at the alpha beta interface upon approaching its lower critical end point. The mechanism of reappearance of suspended drops at the alpha beta interface is carefully observed by the enhanced video microscopy system. It is found that these suspended drops are made of the gamma phase, and are formed by a very slow process of aggregation of very small drops. The contact angle theta spanned by the alpha gamma and beta gamma interfaces of a gamma phase suspended drop at the alpha beta interface is verified to be a quasiequilibrium property. In addition, the interfacial tension resulting from the profile of a suspended drop below the alpha beta interface is consistent with the tension of beta gamma interface sigma(beta gamma) by the pendant drop digitization method. A variety of wetting/nonwetting behaviors as well as wetting transitions is also discussed. It is found that there is a beta phase wetting layer separating the air and the alpha phase. (C) 1996 American Institute of Physics.