Dispersion Polymerization of Methyl Methacrylate Using Poly(vinyl acetate/vinyl propionate) Based Copolymers as Stabilizers in Supercritical Carbon Dioxide

Carbon dioxide is a well-known green solvent, and can be used instead of some organic solvent to prepare the polymer products. On the basis of its poor solubility, dispersion polymerization can be adopted to produce the polymer products in industry. Thus, low price, easily available stabilizers with good stabilization effect will be a must. In this paper, we are committed to designing and synthesizing stabilizers with these characteristics. Firstly, thiol ethanol is used as the chain-transfer agent to control the copolymerization of vinyl acetate/vinyl propionate, and the homopolymers or copolymers with the hydroxyl group at the chain terminal are obtained. These homopolymers or copolymers are then functionalized to prepare the stabilizers with methacrylate groups. The results indicate that these stabilizers can effectively control the dispersion polymerization of methyl methacrylate in supercritical carbon dioxide. The proportion of structural units in the copolymer and the concentration of stabilizer or initiator obviously affect the conversion percentage of methyl methacrylate and the molecular weight of polymers. The maximum conversion percentage of methyl methacrylate and the molecular weight of poly(methyl methacrylate) can reach 93%, and 56000 Da, respectively. SEM images show that most of the samples are free-flowing powders with a spherical structure.