Copolymerization of acrylic acid with styrene in supercritical carbon dioxide

A series of hydrophobically associating polymers were synthesized in suppercritical carbon dioxide by copolymerization acrylic acid with different amounts of styrene at 65 degrees C. The effects of the pressure of CO2 and the concentrations of styrene were observed. The structure and compositions of the copolymer were determined by IR, UV and H-1 NMR spectra. The products were perfect white solid powder. Different pressures and contents of styrene led to different morphology of the products and yields. The conversion of each comonomer was above 90% when the mass fration of styrene in the comonomers was below 5% at 15-19 Wa and 65 degrees C. The viscosities of aqueous solution of the copolymers showed an obvious dependence on pH and shearing time, which suggests that the copolymers can hydrophobically associate in aquatic solution.