Supercritical carbon dioxide microemulsion stabilized with zwitterionic surfactant: A dissipative particle dynamics simulation study

Abstract

Supercritical carbon dioxide can be regarded as a green organic solvent, which has essential application prospects. Supercritical carbon dioxide can replace the oil phase in a conventional microemulsion system. In this work, supercritical carbon dioxide in water (C/W) microemulsion is constructed by a zwitterionic surfactant (CAPB) by the Dissipative particle dynamics (DPD) simulation method. The internal structures of the C/W microemulsion can been intuitively exhibited by the translucent three-dimensional diagrams. The stretching degree of the molecular chain at the C-W interface is reflected by the end to end distance of the surfactant molecule. Research results prove that supercritical carbon dioxide is entirely wrapped by water forming C/W microemulsion when the ratio of water and carbon dioxide increases to 4:1. The CAPB molecules became more aligned with larger end to end distance after forming the C/W microemulsion. The stability studies show that the formed C/W microemulsion has better stability to resist the salt, temperature and shear rate due to the surfactant adsorption layer. The findings open an avenue in the production of C/W microemulsion, which would push forward future application in material synthesis, chemical reactions, and extraction.