Precipitation copolymerization of methyl methacrylate/meth-acrylate acid in supercritical carbon dioxide

Utilizing 2,2′-azobis(isobutyronitrile) (AIBN) as the initiator, the copolymerization of methyl methacrylate/methacrylate acid is performed by precipitation copolymerization. The effects of pressure, initiation concentration, the methacrylic acid (MA) concentration, and small amount of water are investigated separately. The morphology and molecular weight are analyzed by scanning electron microscopy and gel permeation chromatography, respectively. The results indicates that the concentration of MA or AIBN affects the molecular weight greatly, and the maximum molecular weight reaches 213 kDa. The morphology of samples exhibits a certain degree of agglomeration. Most samples are obtained as free-flowing powder with numerous spherical bulges under a proper polymerization condition.