Kinetic Modeling of Crosslinked Thiol-yne Polymerizations

Thiol-yne polymerizations have emerged as a promising approach for creating materials with tailorable chemical, optical, and mechanical properties due to the dual reaction of the alkyne functional group. This work presents the first comprehensive kinetic model for thiol-yne polymerization, incorporating sequential reaction pathways, radical concentration balances, and diffusion limitations via free volume theory. The model shows qualitative agreement with experimental concentration profiles and accurately predicts the effects of changing the reactivity ratio between the first and second reaction pathways. The two sequential pathways are known to compete for thiyl radicals, and this competition is explored through the discovery of intermediate accelerated kinetics, where the thiol consumption rate increases as the reaction progresses. Non-stoichiometric reactions are also explored to determine if the polymerization stopped due to vitrification or limiting reactant. These results provide fundamental insights into thiol-yne reaction kinetics and provide guidelines for rational monomer selection.