Enhancement of the CO2-philicity of poly(vinyl ester)s by end-group modification with branched chains

Four copolymers of vinyl acetate (VAc) and comonomers with different branched chains-dipropyl maleate (DPM), dibutyl maleate (DBM), diisobutyl fumarate (DiBF) and dineopentyl maleate (DNM)-were synthesised, and their CO2-philicity was evaluated by cloud point measurements. It was shown that poly(VAc-alt-DNM), containing the highest branched structure degree, had a 10% lower cloud point pressure at 40 degrees C than poly(VA-calt-DBM)'s, the best CO2-philic hydrocarbon polymer available. Both ab initio calculations and molecular dynamics (MD) simulations showed that the highly branched structure weakened polymer CO2 interactions. However, the MD results for the cohesive energy density, solubility parameter, free volume fraction and radial distribution functions indicated that the more highly branched end groups contributed to an increase in the free volume fraction of the polymer, leading to low polymer polymer interactions. Thus, the introduction of highly branched end groups into the polymer backbone was an efficient way to enhance the CO2-philicity of hydrocarbon polymers.