Static Light Scattering Monitoring and Kinetic Modeling of Polyacrylamide Hydrogel Synthesis

Abstract

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 different 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.

Tunable Thiol–Ene Photo-Cross-Linked Chitosan-Based Hydrogels for Biomedical Applications

“…The solid-like contribution arises from heterogeneous crosslinking, leading to densely and poorly reticulated areas. 35 These inhomogeneities are typically described by one of the…”

Tuneable Thiol-Ene Photo-Crosslinked Chitosan-Based Hydrogels for Biomedical Applications

“…The solid-like contribution arises from heterogeneous crosslinking, leading to densely and poorly reticulated areas. 31 These inhomogeneities are typically described by one of the following functions: another Gaussian term, an exponential function or with the Debye-Buesche-Anderson (DAB) model. 31,32 thiol-ene chemistry, a chemically similar system to ours.…”

“…31 These inhomogeneities are typically described by one of the following functions: another Gaussian term, an exponential function or with the Debye-Buesche-Anderson (DAB) model. 31,32 thiol-ene chemistry, a chemically similar system to ours. 34 In addition, the introduction of the exponent m on the Lorentzian term allows to account for hydrogen bond rich networks, frequent in polysaccharide-based hydrogels, for which a deviation on IL(q) has been observed.…”

Tuneable Thiol-Ene Photo-Crosslinked Chitosan-Based Hydrogels for Biomedical Applications

“…The solid-like contribution arises from heterogeneous crosslinking, leading to densely and poorly reticulated areas. 31 These inhomogeneities are typically described by one of the…”

“…following functions: another Gaussian term, an exponential function or with the Debye-Buesche-Anderson (DAB) model 31,. 32 …”