where Δ𝐻 ° and Δ𝑆 °are the standard state enthalpy and entropy of polymerization, respectably, and R is the ideal gas constant. Polymerization reactions that are generally considered irreversible are typically exergonic to the extent of having negligibly low equilibrium concentrations and thus negligibly low rates of depropagation under most experimental conditions (e.g., the equilibrium concentration of styrene at 298K is 1 𝜇M). When monomers that exhibit reversible propagation are used in copolymerization, the rates of depropagation must be accounted for to accurately characterize the system (vide infra). respectively. While such effects are in some cases required to accurately model copolymerization kinetics, the large number of addition parameters are known to complicate analysis and lead to non-uniqueness in best fit values of reactivity ratios. The equilibrium concentration as defined in Eqn. 3 is identical to the ratios of rate coefficients for homopropagation and depropagation from a terminal dyad for each monomer type: