A Modeling Investigation of Chain Length Dependent Termination during Multivinyl Free Radical Chain Photopolymerizations:  Accounting for the Gel

Abstract

A mathematical model of multivinyl monomer free radical photopolymerizations that takes into account chain length dependent termination (CLDT) and gel formation (an infinite network) was utilized to obtain a more accurate picture of network formation and multivinyl monomer photopolymerization kinetics. The model predicts an increased probability that a radical chain is attached to the gel with increasing chain length and double bond conversion. Accounting for CLDT delays radical incorporation into the gel and induces gel formation at earlier double bond conversions. Increasing the initiation rate also delays gel formation. When the model is expanded to account for the probability that a highly mobile sol radical reacts to become a nearly immobile gel radical, the importance of CLDT prior to reaction diffusion-controlled termination is increased. This result is attributed to bimolecular termination occurring between a short (<10-mer) sol radical and a long gel radical (short−long radical termination). The transition from a CLDT important regime to reaction diffusion-controlled termination is characterized by a transition from primarily short−long to primarily long−long (gel−gel) radical termination.

A Review of Modeling of Diffusion Controlled Polymerization Reactions

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Toward an enhanced understanding and implementation of photopolymerization reactions

“…Here, the polymerization rate does not scale with the classical, idealized 0.5 exponent because, as the initiation rate increases, the kinetic chains become shorter and the radicals more mobile so that they terminate more rapidly. Ultimately, this complex behavior results in a termination kinetic constant that must account for radicals of length i terminating with radicals of length j, [80][81][82] …”

Acrylate Network Formation by Free‐Radical Polymerization Modeled Using Random Graphs

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