UNDERSTANDING THE BEHAVIOUR OF SULPHUR-CENTRED RADICALS DURING POLYMER SELF-HEALING

Authors : İsa DEGİRMENCİ, Michelle L Coote

Pages : 707-720

Doi:10.18596/jotcsa.287305

View : 11 | Download : 6

Publication Date : 2017-01-08

Article Type : Research Paper

Abstract :High-level ab initio molecular orbital theory calculations have been used to study self-healing mechanism of materials based on thiuram disulfides and their derivatives insert ignore into journalissuearticles values(S=Cinsert ignore into journalissuearticles values(Z);S–SCinsert ignore into journalissuearticles values(Z);=S, for Z = CH 3 , NEt 2 , Ninsert ignore into journalissuearticles values(Et);CH 2 CH 2 OH, Ph, Bz);, and the effects of these Z-substituents on their efficacy. The relative contributions of cross-over and reversible addition fragmentation chain transfer reactions were ascertained, and the likelihood of chain-breaking side reactions was assessed. To rationalize the results, the various stabilization energies of the radicals and closed-shell species were also evaluated. The study revealed that the self-healing mechanism of thiuram disulfides follows predominantly the cross-over reaction because of the high energies of intermediate radicals in the chain transfer mechanism. Based on the study, the most effective self-healing materials are predicted to contain amines as Z-groups, while those containing benzyl and its derivatives are most likely to undergo side reactions.
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