A kinetic model describing aqueous acrylamide homopolymerization and copolymerization
of acrylamide with methylene bisacrylamide, leading to hydrogel formation, is presented and applied
in the simulation of these reaction processes. This modeling approach is based on population balances
of generating functions and, besides the crosslinking mechanisms inherent to network formation,
other specific kinetic steps important in acrylamide polymerization (e.g., branching due to backbiting)
are considered in the simulation tool developed. The synthesis of acrylamide polymers and hydrogels
was performed at 26 C and at 40 C using two di erent initiation systems. The formation of such
materials was monitored using in-line static light scattering (SLS), and the spatial inhomogeneity
of the final hydrogels was also measured using this experimental technique. It is shown that the
simulations are helpful in describing information provided by SLS in-line monitoring, namely in
the early stages of polymerization with the transition from dilute to semi-dilute regime. Indeed,
it finds a plausible match between the critical overlap polymer concentration and gelation, this later
leading to the observed spatial heterogeneity of the hydrogels. Usefulness of the kinetic model
for defining operation conditions (initial composition, semi-batch feed policies, chain transfer, etc.)
in making the shift from gelation to the semi-dilute regime is discussed, and the extension of this
approach to processes enabling a higher control of gelation (e.g., controlled radical polymerization) is
also prospected.
This research was funded by project AIProcMat@N2020 (NORTE-01-0145-FEDER-000006) and project
POCI-01-0145-FEDER-006984—Associate Laboratory LSRE-LCM.
