Copolymerization of fluorocarbon-modified poly(acrylic acid) in supercritical carbon dioxide

Copolymer of 1, 1-dihydroperfluorooctyl acrylate (FOA) and acrylic acid (AA) was obtained in supercritical CO2 (SC-CO2). Compared with the traditional methods, the yield ratio of FOA using SC-CO2 is increased at lower temperature, the reaction time is shortened from 24 h to only 4 h, and the products are easier to be treated. At the same time it was found that temperature played an important role in these reactions. The FOA monomer is more active than the AA monomer in low temperature ( T < 55.0 degreesC), but in high temperature ( T > 60.0 degreesC) the activity of AA monomer improved greatly. The viscosity of aqueous solutions of the copolylmers rises up dramatically with the increase of fluorocarbon content, and the viscosity of the copolymers versus pH values shows a peak, both of results evidenced the hydrophobic association of macromolecules in solutions.