Effects of Non-solvent Type and Purification Process on Precipitation Polymerization of Acrylic Acid in Organic Media

Precipitation polymerization is a non-homogeneous free radical polymerization method in which polymer chains are separated from continuous phase as polymer particles. In this method, all polymerization reactions occur in continuous phase as well as in polymer dispersed phase. We found that the initial concentrations of initiator and monomer are determining factors in polymerization behaviour. Unlike the other free radical polymerization methods, termination by precipitation induces the formation of polymer chains with similar chain length to take over bimolecular termination. Thus, the number- and weight-average degree of polymerization depends slightly on the reaction time. In this work, the yield of reaction was measured using a gravimetric method. The yield of reaction and number- and weight-average degree of polymerization of polymer particles were found to be dependent on the non-solvent type and purification process. When the solubility parameter differences of non-solvent and polymer decrease, the yield of reaction dropps but the Mn and Mw tended to increase. The purification process affected the yield of reaction and molecular weights through the oligomer sedimentation. We concluded that polydispersity index (PDI) of precipitation polymerization is lower than that of the free radical homogeneous and heterogeneous polymerization methods.