Mechanism of oxidative destruction of polyvinyl alcohol under the action of ozone-oxygen mixture in aqueous solutions

In this paper, experimental results on the kinetics of accumulation of COOH groups and the kinetics of destructive transformations in the processes of ozonized oxidation of polyvinyl alcohol (PVA) in aqueous solutions are presented. Mathematical modeling of the oxidative destruction of the polymer in the studied reaction system “PVA + O3 + O2 + H2O” has been carried out. The kinetic scheme was compiled on the basis of currently available experimental results on the oxidation and destruction of PVA, taking into account the known concepts of low- and high-molecular organic compounds oxidation mechanisms in the liquid phase. Using the “KhimKinOptima” software package, the inverse and direct problems of chemical kinetics have been solved, which made it possible to determine the rate constants of the key stages of the process under study and obtain the kinetic curves of its participants. It is shown that the proposed kinetic scheme has a good agreement between the calculation and the experiment, the possibility of explaining all the accumulated experimental results, and good predictive ability. The kinetics of accumulation of COOH groups in the “PVA + O3 + O2 + H2O” reaction system with the introduction of an additional initiator, Fenton's reagent (H2O2 + FeSO4), was studied. By solving the direct problem of chemical kinetics, performed using the “KhimKinOptima” software package, the kinetic curves of the participants in the ozonized oxidation of polyvinyl alcohol in the new reaction system were obtained. The results showed that the theoretical curve for the accumulation of COOH groups in the “PVA + O3 + O2 + H2O2 + FeSO4 + H2O” reaction system completely coincided with the experimentally found kinetic curve, which additionally confirms the correctness of the discussed scheme. The kinetic scheme proposed in this work opens up opportunities for controlling the oxidative process in order to obtain oxidized polymer fractions with certain molecular weights. These fractions should be considered as potential substrates for long-acting drugs.