Design And RAFT Synthesis Of CO₂-Philic Poly（Vinyl Acetate）

Supercritical carbon dioxide (scCO2) has been considered to be a green substitude for organic solvent recently because it is nonflammable, nontoxic and naturally abundant. However, carbon dioxide is a relatively poor solvent of most material:for exampe, materials including polar or high molecular weight polymers exhibit low solubility in scCO2. This problem can be solved by developing surfactants and phase transfer agents to disperse poorly soluble materials in scCO2. Therefore, the discovery of inexpensive CO2-philes is an challenge. In this work, a linear CO2-philic homopolymer was firstly synthsized by reversible addition fragmentation chain transfer polymerization (RAFT). Secondly, a R-core star xanthate agent was prepared. The multi-arm R-core star xanthate agent was then used as the RAFT agent, in which the reactive RAFT groups, i.e., the thiocarbonylthio groups, grew away from the core with the growing polymer arm so that the R-core star PVAc with low molecular weight (Mn< 10,000 g/mol) and narrow molecular weight distribution (Mw/Mn< 1.1) was synthesized. Thereafter, the RAFT groups existing at the end of star PVAc could be easily removed via a radical-induced reduction.