Effects of cosolvent on dissolution behaviors of PVAc in supercritical CO2: A molecular dynamics study.

• PVAc could be dissolved in CO 2 when the pressure was much higher than 30 MPa. • Cosolvents could decrease the transition points of PVAc in CO 2. • The mixtures of CO 2 and cosolvents have the solubility parameters close to PVAc. • The LA-LB interactions are the main influence factor of PVAc dissolving in CO 2. • The generated new interactions by cosolvents have great influence. The dissolution behavior of polymers in CO 2 has become increasingly important to the applications of CO 2 in industry. Experimental results showed that PVAc could be dissolved in CO 2 at a high pressure. When cosolvents such as ethanol, acetic acid, and ethyl acetate were present in the system, the transition points could be decreased with the increase in cosolvent concentration. In this work, the influence mechanisms of cosolvents on dissolution behaviors of PVAc in supercritical CO 2 were investigated by molecular dynamics simulation methods. First, the cohesive energy and solubility parameters of PVAc, cosolvents and CO 2 were analyzed. Compared with CO 2 , the mixtures of CO 2 and cosolvents have closer solubility parameters with PVAc to enhance the dissolubility of PVAc within them. Moreover, the mechanism of PVAc dissolution in CO 2 and the effects of cosolvents on decreasing the transition points were investigated. The Lewis acid–Lewis base (LA-LB) interactions between O atoms in PVAc and C atoms in CO 2 are the main influencing factors of PVAc dissolution in CO 2. The presence of cosolvent can generate new interactions, such as hydrogen bonding and LA-LB interactions, which have different influences on the LA-LB interactions between PVAc and CO 2. Ethanol and ethyl acetate have no great influence on these LA-LB interactions, while acetic acid exerts considerable influence. [ABSTRACT FROM AUTHOR]