Imine Based Self-Healing Hydrogel Triggered by Periodate

02 July 2020, Version 1
This content is a preprint and has not undergone peer review at the time of posting.

Abstract

Design of materials with novel sensitivities and smart behaviour is important for the development of smart systems with automated responsiveness. We have recently reported the synthesis of hydrogels, cross-linked by N,N'-diallyltartardiamide (DAT). The covalent DAT-crosslinking points have vicinal diols which can be easily cleaved with periodate, generating valuable a-oxo-aldehyde functional groups, useful for further chemical modification. Based on those findings, we envisioned that a self-healable hydrogel could be obtained by incorporation of primary amino functional groups, from 2-aminoethyl methacrylate hydrochloride (AEMA), coexisting with DAT into the same network. The a-oxo-aldehyde groups generated after the reaction with periodate would arise in the immediate environment of amine groups to form imine cross-links. For this purpose, DAT-crosslinked hydrogels were synthesized and carefully characterized. The cleavage of DAT-crosslinks with periodate promoted changes in the mechanical and swelling properties of the materials. As expected, a self-healing behavior was observed, based on the spontaneous formation of imine covalent bonds. In addition, we surprisingly found a combination of fast vicinal diols cleavage and a low speed self-crosslinking reaction by imine formation. Consequently, it was found a time-window in which a periodate-treated polymer was obtained in a transient liquid state, which can be exploited to choose the final shape of the material, before automated gelling. The singular properties attained on these hydrogels could be useful for developing sensors, actuators, among other smart systems.

Keywords

alpha-oxo-aldehyde
imine
periodate
N,N'-diallyltartardiamide
α-oxoaldehyde
2-aminoethyl methacrylate
self-healing

Supplementary materials

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