Changes in morphology of three-phase emulsions with temperature in ternary amphiphile/oil/water systems

The morphologies of the three phases (aqueous or bottom phase B, middle-phase microemulsion M, and oleic or top phase T) of the ternary 2-butoxyethanol/n-decane/water system were examined at various temperatures and water-to-oil ratios (WORs). There are various hypotheses regarding the effect of temperature on three-phase emulsion morphology. One states that three-phase emulsions should always be M-continuous, irrespective of temperature and the WOR. Another states that three-phase emulsions should be B-continuous at temperatures lower than the phase inversion temperature (PIT) and T-continuous at temperatures higher than the PIT and that the inversion line separating the B-continuous and T-continuous region is horizontal in the three-phase body of the fish diagram. r, measurements recorded in the current study indicated that the inversion line dividing the three-phase body of the ‘fish’ diagram is almost vertical, thereby completely contradicting those previous hypotheses. Moreover, the three-phase emulsion morphologies obtained are found to depend on the WOR. In the region right to the inversion line, the morphology remains M-continuous, irrespective of the WOR, yet in the region left to the inversion line, the morphology is M-continuous at a WOR <1, T-continuous or B-continuous at a WOR ≈ 1, and B-continuous at a WOR >1 Accordingly, the current results are proposed as a new model for the morphology of three-phase emulsions in the fish diagram.