Reinforcement of Optically Healable Supramolecular Polymers with Cellulose Nanocrystals

Abstract

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.

Nanocellulose properties and applications in colloids and interfaces

“…This approach enabled homogenous dispersion of the fibrils into the polymer matrix leading to improvement in the tensile strength and elastic modulus. Composites polystyrene solutions loaded with CNC using a common solvent and nonionic surfactants as compatibilizers have been reported in the form of electrospun fibers ) or films (Kim et al 2009) while telechelic poly(ethylene-co-butylene) was end-functionalized with a pyridine-based ligands to produce light-healable nanocomposites based on CNC (Coulibaly et al 2014).…”

Light-Induced Bonding and Debonding with Supramolecular Adhesives

“…This work demonstrates that supramolecular polymers can be bonded, debonded, and rebonded on demand. Recent studies from our group have shown that the mechanical properties of the supramolecular polymers used here can be tailored by introduction of cellulose nanocrystals, 43,45 and one can expect that this approach can also be used to increase the maximum shear stress when used as adhesives. was applied, and the force was monitored as a function of time.…”

Healable supramolecular polymer solids

“…Extending this work, Coulibaly and coworkers recently reported similar light-healable nanocomposites based on a CNC-reinforced metallosupramolecular polymer synthesized by endfunctionalization of a telechelic PEB with Mebip ligands followed by coordination with a Zn salt ( Figure 5) (vide supra) [110]. As discussed above, the UV-light absorbed by the metal complex is converted into heat with concomitant temporary dissociation of the metal-ligand motifs, which triggers the healing process.…”