Synthesis And CO₂-Philicity Investigation Of Poly（Vinyl Acetate） And Its Derivatives With Different Molecular Structure

Supercritical carbon dioxide (scCO2) is of great interest as a potential alternative to the organic solvent for industrial applications. However, it needs CO2-philic segments as activities to improve the dissolving capacity of polymers in CO2 because its weak polarity. This work aims at investigating the effect of molecular weight (Mn), molecular structure, monomeric unit and end group on the CO2-philicity of poly(vinyl acetate) (PVAc) and its derivatives. Chain transfer agents were synthesized with different molecular structure and then used as reversible addition fragmentation chain transfer polymerization (RAFT) agents to prepare PVAc and poly(vinyl acetate-alt-dibutyl maleate) (PVAc-alt-PDBM) with low Mn and well-defined Mn distributions. The dissolution behavior results found that the cloud point pressures (Pc) of both 3-armed and 4-armed PVAc first decreased, reaching a minimum at a given Mn and then increased, which was different from the variation trend of the Pc of the linear PVAc versus Mn. The Pc of muti-armed PVAc-alt-PDBM was not significantly reduced comparing to that of muti-armed PVAc. In addition, the removal of the xanthate groups could effectively enhance the CO2-philicity of the PVAc, especially at low Mn. The surface tension and glass transition temperature results evidenced the prominent role played by polymer-polymer interaction and entropy of mixing.