Design, Preparation And Characterization Of CO₂-soluble PVAc By RAFT Polymerization

Supercritical carbon dioxide is well known for use as a green processing solvent in chemical industry applications such as extraction, polymerization, organic reactions, biocatalysis, nanoparticle synthesis and separations, because of its low cost, nontoxicity, mild critical point, and nonflammability. Its gas-like diffusivity and liquid-like density allow replacing conventional, often noxious, solvents with supercritical CO₂.In spite of all the recognized advantages of CO₂-based technologies, their applicability is often limited by the fact that CO₂ is a poor solvent to many solutes of interests. Suitable surfactants can be used to overcome some of the limitations associated with processing species that are weakly solvated by CO₂. But the majority of systems reported so far have been highly fluorine-substituted, and the associated costs and low biodegradability may prohibit industrial-scale use in the key applications. The discovery of inexpensive CO₂-soluble materials or CO₂-philes is therefore an important challenge. OVAc is an inexpensive, high-tonnaged bulk commodity polymer which, unlike most vinyl polymers, is moderately biodegradable. OVAc has been shown to exhibit anomalously high solubility in CO₂ with respect to other vinyl hydrocarbon polymers. But the polymer is soluble only at relatively low molecular weights under conditions of practical relevance (P<300bar, T<100℃).The method of establishing OVAc is, usually through an extraction of PVAc in supercritical fluid, time-consumed and low effective. So the study presented here is a rapid method to produce well-defined OVAc through employing reversible addition fragmentation chain transfer (RAFT) polymerization and the influence parameters of preparation OVAc is also investigated.In the first part of this work, a detail background of this thesis was reported, which provided the importance of this study.In the second part of this work, a study of the synthesis and characterization of 2-Ethoxythiocarbonylsulfanyl-propionic acid methyl ester (EOSPE) was reported, which is an effective chain transfer agent for VAc's RAFT polymerization. In the third part of this work, the low molecular weight and well-defined poly(vinyl acetate) was prepared via RAFT polymerization, performed with the aim to possibly modify to the polymer as a surfactant in supercritical CO₂, and the influence parameters of preparation PVAc was also investigated. Topography, structure and molecular weight of poly(vinyl acetate) were examined with FT-IR,¹H NMR and GPC.