Wetting transitions at the air–liquid interface of water+tetradecane+C6E2 mixtures

Abstract

In this study, the interfacial phenomena and the wetting behaviors of the ternary system water+tetradecane+diethylene glycol monohexyl ether (C6E2) were carefully examined at 20 °C. There is one three-liquid-phase-coexisting tie triangle and three two-liquid-phase-coexisting envelopes in the triangle phase diagram of the system water+tetradecane+C6E2 at 20 °C. In the two-liquid-phase-coexisting region on the water/C6E2 side, the upper C6E2-rich liquid phase exhibits a sequence of transition: nonwetting→partial wetting→complete wetting at the lower aqueous phase/air interface by simply varying the system composition. Similarly, in another two-liquid-phase-coexisting region on the tetradecane/C6E2 side, the upper tetradecane-rich liquid phase also demonstrates a sequence of transition at the lower C6E2-rich phase/air interface. Some of these wetting transitions can be deduced by the critical wetting theory of Cahn, while the other transitions seem to have no obvious relevance to a critical end point.