Phase inversion temperature additive effect

The previous stability discussion does not apply to microemulsions because they are thermodynamically stable isotropic solutions. Microemulsions differ from macroemulsions in that their oil-surfactant components can exist as cylindrical or bicontinuous strucmres in addition to spheroids (9). The stability and structure of nonionic microemulsions is governed by temperature. As the temperature is increased to the phase inversion temperature (PIT), the structure converts to bicontinuous and then it inverts as the PIT is exceeded. Similar effects can be accomplished for ionic microemulsions by adding electrolyte and certain cosurfactants. Microemulsions may also lose stability when diluted. 

The effect of additives in the water and oil phases. Although the exact mechanism by which various additives affect the phase inversion is not fully understood, their presence in nSOW systems has been shown to affect the PIT as well as the emulsion inversion point, EIP. " The phase inversion temperature varies with the amount and chemical type of additives in the water phase. Shinoda and Takeda showed that inorganic salts can affect the PIT more strongly than their parent acids. Also, they showed that the effect of fatty acids and alcohols on the PIT for 1 1 volume ratio paraffin-water systems was independent of the chain length of the acid or alcohol. 

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