Influence of n-alkyl ester groups on efficiency of crosslinking for methacrylate monomers copolymerized with EGDMA: Experiments and Monte Carlo simulations of reaction kinetics and sol-gel structure

- Crosslinking reactions are studied using a hybrid Monte Carlo simulation approach.
- Ester side chains hinder chain-end propagation with crosslinker pendent vinyl groups.
- A single parameter ΨC,X can define the reduction in pendent vinyl group reactivity.
- The parameter ΨC,X is uniquely determined for each n-alkyl methacrylate/EGDMA pair.

We present the results of applying a computationally efficient Monte Carlo (MC) method to simulate the reaction kinetics and molecular architecture development during free-radical, bulk copolymerizations of a homologous series of methacrylate monomers with ethylene glycol dimethacrylate. The overall objective of the work was to determine the extent to which the ester side chains of the methacrylate monomers hinder chain-end radical propagation reactions through the pendent vinyl groups of the crosslinking monomer. We have determined that this steric hindrance is quite significant and increases with ester side chain length. This is expressed by a reduced reactivity parameter, ΨC,X, that is different for each monomer-crosslinker pair. With this single kinetic parameter adjustment, the MC model was able to effectively predict the reaction kinetics, gel points, and sol−gel fractions throughout the entire reactions, including, to a limited extent, the solvent swelling ratio of the gel for two different levels of crosslinker.

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