Highly tough, multi-stimuli-responsive, and fast self-healing supramolecular networks toward strain sensor application

Abstract

This work demonstrated heat- and light-responsive supramolecular networks having high toughness, shape memory and self-healing properties. The supramolecular networks were composed of covalent and transient crosslinks that were formed by crystalline poly(ethylene glycol) (PEG) and poly(ε-caprolactone) (PCL) and by 2-ureido-4-pyrimidone (UPy) supramolecular moieties. The resultant supramolecular networks realized exceptional mechanical performance such as tensile stress of 7.2 MPa and toughness of 25.2 MJ m−3. By utilizing the light-to-heat conversion capability of UPy moieties, the polymer films could be heated up to ~63 °C under UV light irradiation, which was sufficient to activate the temperature-dependent shape memory and self-healing properties. Consequently, supramolecular polymers were responsive to the heat as well as the light irradiation, and the latter resulted in faster and desirable shape memory effect. Furthermore, the direct heating and the photoeffect heating could enable the self-healing of the damage via dynamic reversibility of UPy units. It is noteworthy that the light-induced healing allowed remote activation, on-demand treatment, faster self-healing (1 min) and higher healing efficiency (86%) in comparison with direct heating. The tough self-healing materials enabled the fabrication of durable strain sensors with high toughness and electrical healing ability, indicating their great potentials in the flexible electronic field.