CROSS-LINKING KINETICS IN POLYACRYLAMIDE NETWORKS

Kinetics of network formation in free-radical copolymerization of acrylamide and N,N′-methylenebis-acrylamide in aqueous solution (56.6 g comonomer per litre) at 25°C have been studied. It was found that as high as 80% of pendant double bonds are consumed immediately on polymerization and are wasted in primary cyclization. Primary cyclization is responsible for the delay in the onset of gelation at low mole fractions of divinyl monomer. The effects of decreased reactivity of pendant double bonds and secondary cyclization become significant as the mole fraction of divinyl monomer increases. The decreased reaction rate between huge molecules due to steric hindrance in the pre-gelation period contributes to microgel formation, and consequently to formation of spatially inhomogeneous networks. © 1990.