posted on 2019-01-07, 19:34authored byProgyateg Chakma, Zachary A. Digby, Max P. Shulman, Leah R. Kuhn, Colleen N. Morley, Jessica L. Sparks, Dominik Konkolewicz
Dynamic
nucleophilic exchange of quaternary anilinium salts has
been incorporated into rehealable and malleable polymeric materials
that can be activated under mild (60 °C) thermal stimulus. The
mechanism of dynamic exchange between quaternary anilinium salt and
free aniline was assessed in small-molecule model experiments. The
dynamic exchange was found to be dissociative in nature, due to the
indirect SN2 mechanism, where initially the bromide anion
attacks the anilinium salt to generate an alkyl bromide which undergoes
subsequent attack by a free aniline group. A quaternary anilinium-based
cross-linker was synthesized to act as dynamic linkages in the polymer
network. Cross-linked polymeric materials showed thermoresponsive
rehealing and malleability properties at 60 °C along with being
resistant to irreversible creep under ambient conditions. The use
of anilinium salts enables dynamic exchange to occur with significantly
milder thermal stimulus than other comparable materials, while maintaining
mechanical stability.