In the case of the rate constant of β-scission (kβ), an increase is observed with the presence of an electron-withdrawing substituent, with the highest constant computed for the NO2-substituted POT. It appears that electron-donating substituents, on the other hand, do not have a significant influence on the β-scission of the reaction intermediate related to the non-substituted POT. Thus, if we compare the rate constant of propagation of the styrene monomer (kp) with the rate constant of transfer (ktr), we observe that when POT is substituted at the para position of the aryl group with an electron-withdrawing group, the reactivity of the thionolactone in copolymerization with styrene increases significantly, and this effect is more pronounced with stronger electron-withdrawing groups. The kp/ktr values thus indicate the polymerization of the thionolactones first, followed by the polymerization of styrene with a strong compositional drift. Conversely, adding an electron-donating group does not appear to have a major influence on the reactivity of the thionolactones. Similarly, when we examine Figure , which describes the results obtained using our DFT calculation method for the copolymerization of substituted POT with methyl acrylate, we obtain results comparable to those for styrene. Indeed, the addition rate constant increases with the electron-withdrawing effect of the substituent. The reverse addition rate constant is higher when the substituent is electron-donating, and the β-scission rate constant (kβ) increases in the presence of an electron-withdrawing substituent. Thus, the conclusions for the copolymerization of substituted POT with acrylate are similar to the ones with styrene. The kp/ktr value decreases when POT is substituted at the para position of the aryl group with an electron-withdrawing group, making the thionolactone much more reactive in copolymerization with acrylate compared to unsubstituted POT. The notable difference in the copolymerization with acrylate, compared to styrene, is a stronger decrease in the kp/ktr value when an electron-withdrawing group is added. This suggests that, during copolymerization with acrylate, POT substituted with an electron-withdrawing group will be even more reactive than during its copolymerization with styrene. Since unmodified POT exhibits reactivity close to that of styrene and a slight difference with acrylate, indicating a random insertion of the thionolactone for the former and a slight deviation in the insertion of the thionolactone during copolymerization for the latter, it is expected that substituting the POT thionolactone with an electron-withdrawing group will make this insertion less random and thus less effective in the context of degradable polymers. Indeed, the substituted thionolactone is likely to exhibit increased reactivity compared to POT with both styrene and acrylate. Therefore, the next part of this study focuses on the synthesis and copolymerization with vinyl monomers of substituted POT containing groups with significant electronic effects, aiming to validate the theoretical study with experimental data.