Effect of monomer sequence distribution on the CO₂-philicity of a well-defined ternary copolymer: Poly(vinyl acetate-co-vinyl butyrate-co-vinyl butyl ether)

The work aims to interpret the phase behavior of multi-polymers in super critical CO₂ via a spatially dependent structural parameter, the monomer sequence distribution, rather than traditional statistical factors. Well-defined statistical copolymers based on three CO₂-philic monomers, vinyl acetate, vinyl butyrate and vinyl butyl ether, were synthesized with reversible addition-fragmentation chain transfer free-radical polymerization by combining their kinetic behaviors and pairwise reactivity ratios into the Alfrey–Goldfinger–Skeist model. The corresponding cloud point pressures become nonlinear with the polymer composition and possess upper critical solution pressure behavior. Additionally, their diad and triad monomer sequence distributions were calculated by simple theoretical arithmetic. While analyzing the cloud point pressure measurements, we found that both the differences in composition and symmetrical structure of the monomer triads could impact the CO₂-philicity of triads, which were close to the properties of the products, and thus, the variations in the triad sequence distribution could reasonably predict the phase behavior of the products.