Issue 45, 2021

Role of thiol oxidation by air in the mechanism of the self-initiated thermal thiol–ene polymerization

Abstract

A spontaneous thiol–ene polymerization has been reported in the literature for a broad range of monomers, generally under conditions avoiding solvents, heating and the intentional formation of radicals. In the search for a mechanism accounting for the self-initiated thiol–ene polymerization, this study demonstrates the significant role played by thiyl radicals produced by thiol oxidation through dissolved atmospheric oxygen in the thiol–ene mixture. To determine the factors underlying the reactivity, self-initiated polymerization kinetics, thiol solvation and the nature of initiating radicals are studied by means of various techniques including real-time FTIR, 1H NMR spectroscopy and spin-trapping experiments. Our data support that the driving force for thiol air oxidation is the polarization of the S–H bond. Thiol substituents with electron-withdrawing properties and/or hydrogen-bonded thiol–solvent (or thiol–alkene) complexes favor self-initiation by increasing S–H bond polarization, thereby easing the electron transfer to molecular oxygen.

Graphical abstract: Role of thiol oxidation by air in the mechanism of the self-initiated thermal thiol–ene polymerization

Supplementary files

Article information

Article type
Paper
Submitted
28 set 2021
Accepted
28 out 2021
First published
29 out 2021

Polym. Chem., 2021,12, 6594-6605

Role of thiol oxidation by air in the mechanism of the self-initiated thermal thiol–ene polymerization

C. M. Q. Le, F. Morlet-Savary and A. Chemtob, Polym. Chem., 2021, 12, 6594 DOI: 10.1039/D1PY01301G

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