Living organisms with autonomous functions approach the issue of damage and failure in an elegant fashion. They can self-adapt to environmental stimuli to reduce damage, and even warn of and self-heal injuries after damage, which enable them to perform well in challenging environments and promote their lifetime. In this work, we developed nature-inspired strategies towards autonomous polymers with self-adaptive energy absorbability and conductivity restoration, as well as damage self-reporting and self-healing functions.

We first developed an oil-in-oil solvent-evaporation approach to directly microencapsulate an ionic-liquid-based shear thickening fluid (ILSTF) via rheological behavior transition. As the co-solvent completely changed the rheological responses of the dispersed phase, t...[ Read more ]

Living organisms with autonomous functions approach the issue of damage and failure in an elegant fashion. They can self-adapt to environmental stimuli to reduce damage, and even warn of and self-heal injuries after damage, which enable them to perform well in challenging environments and promote their lifetime. In this work, we developed nature-inspired strategies towards autonomous polymers with self-adaptive energy absorbability and conductivity restoration, as well as damage self-reporting and self-healing functions.

We first developed an oil-in-oil solvent-evaporation approach to directly microencapsulate an ionic-liquid-based shear thickening fluid (ILSTF) via rheological behavior transition. As the co-solvent completely changed the rheological responses of the dispersed phase, this approach proved to be ideal for encapsulating STFs with high viscosity and shear-thickening behavior. The resultant ILSTF microcapsules (MCs) exhibited a controllable size at the micrometer level from 66 to 260 μm, and extremely high thermal stability (initial decomposition temperature of ~380 °C). The effects of key factors, including matrix modulus, loading rate, MC size, MC fraction, and MC core type, on the energy absorption capacity of ILSTF MC-modified composites were investigated systematically. Furthermore, the circuit comprised of ILSTF MCs-incorporated flexible conductor exhibited not only electrical stability upon impact, but also autonomic conductivity restoration after injury, demonstrating that the ILSTF MCs can serve as a multifunctional agent for emerging applications, such as deformable circuits and battery safety.

In the second approach, we developed a facile strategy to prepare polymer coatings with self-healing and self-reporting by simple integration of single-component MCs containing hexamethylene diisocyanate (HDI) and aggregation-induced emission luminogen (AIEgen) into the matrix. The AIEgen/HDI MC-embedded coatings displayed adaptive self-repair of scratches based on the spontaneous reaction between HDI and water, as well as a simultaneous high-contrast indication of the healed damage based on restriction of intramolecular motions working mechanism of AIEgens. Furthermore, environmental-sensitive AIEgens, twisted intramolecular-charge-transfer (TICT)-type AIEgens, were utilized as the indicator to achieve the visualization and monitoring of damaging-healing processes of polymers. During the self-healing polymerization, the damaged regions exhibited dual-fluorescence signals with a blueshift of emission color and an increase in emission intensity because of the increasing restriction. The multifunctional MC-embedded polymer coating enjoys the advantages of real-time, on-site, and full-field indication of the health state.

On the basis of this work, we open up new opportunities for the development of autonomous polymers with self-adaptive, self-reporting, and self-healing functions, which can effectively prolong the service life of polymers.