Molecular dynamics simulation of CO2 in organic solvent and polymer–solvent solutions

Abstract

ScCO₂ spray coating through blending CO₂ with common coating solutions has become an environmentally friendly process in industrial spray coating application. Understanding the structural and diffusion properties of CO₂ in solvents and polymer solution is important for ScCO₂ spray coating. In this article, molecular dynamics simulation was performed to study the structural properties and diffusion coefficients in ScCO₂-organic solvent binary mixtures and ScCO₂-organic solvent-polymer ternary mixtures. The density of mixture is increased with increasing the mass fraction of CO₂ for most of studied solvents and the solubility parameter of the binary mixtures decreased approximately linearly. Furthermore, using poly(methyl methacrylate/n-butyl acrylate) [P(MMA/nBA)] as coating resin, the microstructures and interactions of CO₂, organic solvents and polymer in ternary mixtures were investigated through the diffusion and radial distribution function. It was found that the density and diffusivity of ternary mixtures also increased with increasing CO₂ content. Moreover, the number of the replacement of solvent molecules by CO₂ molecules is lower due to the higher interaction between n-butanol and [P(MMA/nBA)].