Monte Carlo Simulations of Free Radical Polymerizations
with Divinyl Cross-Linker: Pre- and Postgel Simulations of Reaction
Kinetics and Molecular Structure
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Abstract
A computationally efficient Monte
Carlo method was used to simulate
the reaction kinetics and molecular structure development during free-radical
copolymerizations with divinyl monomers. A single parameter was used
to describe the reduced reactivity of the pendent vinyl groups incorporated
within the polymer backbone. The simulation results were compared
with published experimental data for the bulk copolymerization of
methyl methacrylate with different levels of ethylene glycol dimethacrylate.
The model was able to effectively predict the reaction kinetics, the
gel point, and sol–gel fractions in both the pre- and postgel
regimes, including the swelling index of the gel. In the postgel regime
the cross-linked molecule becomes the primary locus of reactions,
and all chains eventually become part of this massive cross-linked
polymer network. The Monte Carlo method allows the determination of
the complete molecular structure as it evolves with time, including
properties like cross-linking density, number of free chain ends,
primary cycles and loops, and the fraction of unreacted pendent vinyl
groups