Dispersion Polymerization of Acrylamide

Abstract

Dispersion polymerization of acrylamide has been successfully carried out in aqueous tert-butyl alcohol (TBA) media (TBA = 50 - 80 vol %) using poly(vinyl methyl ether) (PVME) as the polymeric stabilizer and ammonium persulfate as the initiator. Polydisperse spherical as well as oval particles are formed. The simultaneous presence of both spherical and oval particles suggests the coalescence of similar size particles (homocoalescence) takes place, leading to polydispersity. The increase of stabilizer concentration leads to a decrease in particle size and an increase in molecular weight. An increase of initiator concentration results in an increase in particle size and a decrease in molecular weight. These observations are in conformity with other dispersion polymerizations reported in the literature. Particle size decreases as the TBA concentration increases, i.e. as the medium polarity decreases. TBA-water mixtures exhibit cosolvency toward PVME, the solvency becoming highest at about 70 vol % TBA. This solvency aspect cannot account for the monotonous decrease of particle size with an increase in TBA concentration. A plot of particle diameter (D n ) vs the initial solubility parameter (δ) of the medium gives a straight line unlike the linear relationship between D n and 1/δ reported for dispersion polymerization of nonpolar monomers in polar solvents. This difference in behavior for the two systems can be reconciled ifthe grafted polymer acts as the true stabilizer.