Dynamic
covalent bonds (DCBs), which can undergo reversible cleavage
and reformation upon exposure to readily useable stimuli, have attracted
dramatic attention, but the library of such bonds still remains to
be developed. Herein, we report molecular structures, dynamic behaviors,
and healability of bis(2,2,6,6-tetramethylpiperidin-1-yl)trisulfide
(BITEMPS-S3) to compare with its disulfide analogue (BITEMPS-S2) exchanged
at moderate temperature. Unsymmetrical cleavage of trisulfide linkage
induced relatively rapid disproportionation to di- and tetrasulfide
derivatives. In the bulk, poly(hexyl methacrylate) networks partially
containing the BITEMPS-S3 moiety as a cross-linking point afforded
nearly quantitative damage healability only by simple hot pressing
at 110 °C under mild pressure. A slightly higher healability
of BITEMPS-S2 compared to that of BITEMPS-S3 would be due to the differences
in the chain-transfer reaction for the trisulfide linkage during free-radical
polymerization rather than thermal exchangeability of the BITEMPS-S3
moiety. Therefore, not only BITEMPS-S2 but also BITEMPS-S3 should
be regarded as one of DCBs triggered upon exposure to mild external
stimuli.
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