Study on the Precipitation Polymerization of Acrylamide and Methacrylic Acid in Ethanol by Conductimetry: Phase- Separation Prior to Polymerization

Abstract

Conductimetry was employed to investigate the precipitation polymerization of acrylamide/methacrylic acid (AAm/MAA) in ethanol (EtOH). The conductivity change vs. temperature of AAm/MAA-EtOH as well as the effects of monomer ratio and monomer concentration was studied. An abrupt decrease of conductivity in AAm/MAA-EtOH was observed at ca 25°C, indicating the phase separation of monomers and EtOH. As the ratios of AAm/MAA increased from 2/1 to 5/1 (wt/wt), the phase separation temperature increased from 22 to 31°C. The higher the monomers concentration, the temperature of phase separation is lower. These results proved that the lyophobicity of methyl group of MAA dominated the phase separation and the precipitation polymerization system of AAm/MAA-EtOH, by which the microspheres were prepared, was heterogeneous prior to the polymerization.