Polymers that can be repaired after being damaged are attractive, because this feature can improve the reliability, functionality, and lifetime of these materials. We report here light-healable nanocomposites based on a telechelic poly(ethylene-co-butylene) that was functionalized with hydrogen-bonding ureidopyrimidone (UPy) and cellulose nanocrystals (CNCs) decorated with the same binding motif. These nanocomposites show significantly improved mechanical properties when compared to the supramolecular polymer alone. When these materials are exposed to ultraviolet radiation, the UPy motifs are excited and the absorbed energy is converted into heat. This causes temporary disengagement of the hydrogen-bonding motifs, concomitant with a reversible decrease of the supramolecular polymers’ molecular weight and viscosity. As a result, deliberately introduced defects can be healed quickly and efficiently, even at a filler content of 20% w/w, that is, in compositions that exhibit high strength and stiffness.

We report the preparation and characterization of light-healable nanocomposites based on cellulose nanocrystals (CNCs) and a metallosupramolecular polymer (MSP) assembled from a telechelic poly(ethylene-co-butylene) that was end-functionalized with 2,6-bis(1′-methylbenzimidazolyl) pyridine (Mebip) ligands and Zn(NTf2)2. The polymer absorbs incident ultraviolet (UV) radiation and converts it into heat, which causes dissociation of the metal–ligand motifs. This process liquefies the material, and small defects are readily filled. When the UV light is switched off, the MSP reassembles and the original properties are restored. The introduction of CNCs into the MSP matrix leads to a significant increase of the stiffness and strength, from 52 and 1.7 MPa for the neat polymer to 135 and 5.6 MPa upon introduction of 10% w/w CNCs. The Zn2+ ions bind to the CNCs which means the metal:ligand ratio of the MSP must be adjusted accordingly. In nanocomposites thus made, deliberately introduced defects can be efficiently healed.

We report light-responsive, mechanically switchable, photopatternable nanocomposites based on benzophenone-derivatized cellulose nanocrystals (Bp-CNCs).