The thickening mechanism of CO2 thickener poly (vinyl acetate -vinyl ether) (PVAEE): A molecular dynamics study

Abstract

This paper performed molecular dynamics simulation to calculate the effect of poly (vinyl acetate-vinyl ether) (PVAEE) on the viscosity of CO2 and its thickening mechanism. The main conclusions are as follows: i) With the increasing of PVAEE, the viscosity of CO2 also increases, indicating that the addition of PVAEE can improve the thickening efficiency. VDW potential interaction energy is the main driving force. ii) PVAEE will gradually curl and aggregate under the effect of electrostatic potential energy, forming a certain network structure. The curled PVAEE chains can increase the rigidity and viscosity of the system. iii) Through studying the properties of the Vinyl Acetate (VAc) and Vinyl Ether (VEE) groups under salt ions environment, we found that VAc groups on PVAEE can bind more CO2 and increase viscosity significantly than VEE groups. iiii) Moreover, we also found that CO2 molecules tend to be circularly distributed around the methyl (CH3) groups on the VAc and VEE groups. While Ca2+ and Mg2+ ions tend to be distributed around O atoms of them. Based on the conclusions above, this paper can provide selection and assistance for the synthesis of better CO2 thickeners.