Kinetics of Free-Radical Cross-Linking Polymerization: Comparative Experimental and Numerical Study

Abstract

Modeling free radical polymerization processes in the presence of cross-linkers is a challenging problem that has been addressed using numerous techniques for over more than half a century. However, a model providing a comprehensive description of the phenomenon has not been proposed yet. In this work, we implement a simple free-radical polymerization scheme of a monovinyl (difunctional) monomer and a divinyl (tetrafunctional) cross-linker in a Monte Carlo (MC) scheme, which describes polymer dynamics using a bond-fluctuation model. MC simulations allow us to follow the entire polymerization kinetics and the formation of a percolating network (gel phase) by realistically taking into account diffusion limitations, to extract scaling information at the percolation threshold and to recover the distribution of number of monomer units between two successive fully cross-linked units, from which the extent of swelling can be computed. The predictions of MC simulations are also successfully compared to a kinetic model based on numerical fractionation, with kinetic constants used as fitting parameters. MC data and kinetic simulations are compared to some experimental data on the swelling behavior of polyacrylamide hydrogels and of poly(methyl methacrylate) (PMMA) gels, exhibiting good agreement. We conclude that the proposed MC simulation scheme represents a powerful tool from which precious and experimentally inaccessible information on polymerization processes in the presence of cross-linkers can be extracted.

Barnacle biology before, during and after settlement and metamorphosis: a study of the interface

“…The bacterial staining showed that the ROS was largely distinct from the bacteria and from features of the barnacle. We hypothesize that these ROS at the cuticle layers also contribute to oxidative crosslinking (Okay et al, 1995;Dijkgraaf et al, 2003;Lattuada et al, 2013), as seen in other crustaceans (Willis, 1999;Glazer et al, 2013), and are critical to cuticle development and hardening, as seen in insects (Hopkins and Kramer, 1992;Suderman et al, 2006;Andersen, 2010). Further work is needed to define the specific ROS present and show the extent of their presence during development as only post-metamorphic juveniles were examined.…”

Multiscale approach for the construction of equilibrated all-atom models of a poly(ethylene glycol)-based hydrogel

“…In comparison, the much more efficient 3D BFM method has been successfully used to describe the formation of percolating networks and the dynamics of polymer networks, with its predictions shown to compare well with experimental data. 21,22,[59][60][61][62][63][64][65][66] Moreover, BFM has been proven to be an efficient method to work with branched polymers, [67][68][69] …”

Development of methacrylate/silorane hybrid monomer system: Relationship between photopolymerization behavior and dynamic mechanical properties

“…Considerable effort has been devoted throughout the material science community to quantifying the polymerization process with the goal of predicting the final properties of the polymer network by combining simulations and experimental swelling data. 23 In spite of these efforts, a comprehensive description of the relationship between polymerization kinetics and final crosslink structure remains a challenging problem. The complexity of this problem is increased in the methacrylate-silorane hybrid formulations by variables such as polymerization-induced phase separation.…”