EPR–spin-trapping studies of the heterogeneous oxidative curing of some liquid polysulfide polymers: evidence for the mediation of thiyl radicals, disulfide radical-anions and oxygen-centred radicals

Abstract

The use of spin-trapping techniques (with DMPO and MNP) in conjunction with EPR and NMR spectroscopic studies has allowed mechanistic details to be obtained about the process whereby thiols (particularly liquid polysulfide polymers) can be linked via reaction with inorganic oxidants (especially activated MnO₂). The roles of activation, basic additives, and oxygen are interpreted in terms of the involvement of thiyl radicals which can undergo both dimerization and reaction with thiolate anions, evidently to give disulfide radical-anions as important reaction intermediates.