The formation and stability of microemulsions formed with organic solvent as inner/outer phases: Insight from DPD simulation

Organic solvents are selected as the inner/outer phases to construct the microemulsion systems can open new areas of application in providing a reaction medium for various organic conversions. O/W and reverse W/O microemulsions are prepared, using four different organic solvents of Benzene, Cyclohexane, Octane and Dodecane and nonionic surfactant Dodecylhexaglycol (C12E6) as a stabilizer by using Dissipative particle dynamics (DPD) simulation method. The oil–water ratio is applied to control the topology of the microemulsions and more importantly achieve the transformation of O/W and reverse W/O microemulsions. For cyclic hydrocarbons, Cyclohexane needs the same ratio to form O/W microemulsions and reverse W/O microemulsions with Benzene though possessing the special π chemical bond. However, the liner hydrocarbon with a short molecular chain of Octane is conducive to form O/W microemulsions and the longer chain of Dodecane is easier to create reverse W/O microemulsions. The interfacial tension and end-to-end distance values are lowest when O/W and reverse W/O microemulsions are formed in the system. The temperature-induced stability results show that O/W microemulsions have the same stability for four organic solvents, but Cyclohexane and Octane present superior strength than Benzene and Dodecane for reverse W/O microemulsions. In addition, the more substantial hydrophobic effect of Cyclohexane and Dodecane promotes better salt-induced stability for O/W microemulsions, interestingly, reverse W/O microemulsions present the same stability for four systems. Our findings are instructive in providing the physical understanding necessary for future progress in research and applications of microemulsions, especially for organic solvents as the oil phase in the field of microreactors.