Investigation of interfacial composition and thermodynamic stability of 14-n-14/alcohol/oil/water microemulsions by dilution method

The interfacial composition and thermodynamic parameters of W/O 14-n-14/alcohol/oil/water microemulsions were investigated by dilution method in terms of the number of linking groups n (n = 3–6), water content, alcohol and oil types. The gemini/alcohol/oil/water microemulsion system formed spontaneously with negative Gibbs free energy at 25 ℃. The long carbon chain of alcohol facilitated the formation of W/O microemulsion. With increasing carbon chain length of the oil phase, the absolute value of the Gibbs free energy initially increased and subsequently decreased. With an increasing number of linking groups in gemini surfactants, the amount of alcohol that was required in the interfacial layer increased, thereby hindering alcohol movement from the continuous phase to the interface layer, and the absolute value of the Gibbs free energy also decreased, suggesting that a small value of n is beneficial to the stability of microemulsions.