Formation of monodisperse polyacrylamide particles by radiation-induced dispersion polymerization. I. Synthesis and polymerization kinetics

Highly monodisperse polyacrylamide (PAM) microparticles were directly prepared by radiation-induced dispersion polymerization at room temperature in an aqueous alcohol media 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 influence of the dose rate, monomer concentration, stabilizer content, medium polarity, polymerization temperature on the polymerization rate, and the molecular weight of the polymer was examined. The polymerization rate (Rp) can be represented by Rp ∝ D^0.15[M]^0.86[S]^0.47[A/W]^0.64 and the molecular weight of the polymer can be represented by M_w ∝ D^-0.19 [M]^1.71[S]^0.43[A/W]^0.14 at a definite experimental variation range. The overall activation energy for the rate of polymerization is 10.57 kJ/mol (20-35°C). Based on these experimental results, the polymerization mechanisms were discussed primarily.