FORMATION OF MONODISPERSE POLYACRYLAMIDE PARTICLES BY DISPERSION POLYMERIZATION. I. SYNTHESIS AND POLYMERIZATION KINETICS

ABSTRACT Highly monodisperse polyacrylamide (PAM) microparticles were directly prepared by dispersion polymerization in aqueous alcohol media initiated by 2,2′-azobisisobutyronitrile (AIBN) using poly(N-vinylpyrrolidone) (PVP) as a steric stabilizer. Monomer conversion was studied dilatometrically, and polymer molecular weight was determined viscometrically. The gel effect was found evidently from the polymerization kinetics curves. The influences of initiator concentration, monomer concentration, stabilizer content, medium polarity, polymerization temperature on the polymerization rate and the molecular weight of polymer have been examined. The polymerization rate (Rp) can be represented by Rp∝[I]0.52, [M]1.16, [S]0.52, [A/W]0.25 (at A/W value below 1.25), and the molecular weight of polymer can be represented by Mw∝[I]−0.22, [M]1.46, [S]0.25, [A/W]0.19. The overall activation energy for the rate of polymerization is 48.10 kJ/mol (45–55°C). Based on these experimental results, the polymerization mechanisms were discussed primarily.