Synthesis of oligomer vinyl acetate with different topologies by RAFT/MADIX method and their phase behaviour in supercritical carbon dioxide

Poly(vinyl acetate) (PVAc) has been shown to exhibit anomalously high solubility in CO2 as compared to other vinyl hydrocarbon polymers. Understanding the phase behaviour of PVAc with different topologies in CO2 is very important for its potential applications as suitable surfactant, or phase transfer agent in a CO2 solvent process. In this study, a series of PVAcs with different topologies (bi-arms, tri-arms, tetra-arms) were synthesized by RAFT/MADIX method. The structures and molecular weights of these polymers were characterized by 1H NMR and GPC. The phase behaviours of PVAcs in dense carbon dioxide fluid were determined, and the results show that the PVAc with more arms has lower cloud point pressure.