Tough and Multi‐Recyclable Cross‐Linked Supramolecular Polyureas via Incorporating Noncovalent Bonds into Main‐Chains

Abstract

Covalent thermosets generally exhibit robust mechanical properties, while they are fragile and lack the ability to be reprocessed or recycled. Herein, a new strategy of incorporating noncovalent bonds into main‐chains is developed to construct tough and multi‐recyclable cross‐linked supramolecular polyureas (CSPU), which are prepared via the copolymerization of diisocyanate monomers, noncovalently bonded diamine monomers linked by quadruple hydrogen bonds, and covalent diamine/triamine monomers. The CSPU exhibit remarkable solvent resistance and outstanding mechanical properties owing to the covalent cross‐linking via triamine monomer. Through the incorporation of 9.7% and 14.6% quadruple hydrogen bonded diamine monomer, the transparent CSPU films are endowed with superior toughness of 74.17 and 124.17 MJ m−3, respectively. Impressively, even after five generations of recycling processes, the mechanical properties of reprocessed CSPU can recover more than 95% of their original properties, displaying excellent multiple recyclablity. As a result, the superior toughness, remarkable solvent resistance, high transparency, and excellent multiple recyclability are well‐combined in the CSPU. It is highly anticipated that this line of research will provide a facile and general method to construct various cross‐linked polymer materials with superior recyclability and mechanical properties.

Ultrarobust, tough and highly stretchable self-healing materials based on cartilage-inspired noncovalent assembly nanostructure

“…Xi Zhang and coworkers designed and fabricated both reversible noncovalent bonds and permanent covalent cross-links to improve mechanical stength of elastomer to 34.0 MPa (ref. 33 ). For most self-healing materials, their mechanical strength is still relatively low and not capable of meeting the requirement of structural materials.…”

Dynamics and healing behavior of metallosupramolecular polymers

“…The results agree with computational and interdiffusion studies on other glassy polymers ( 8 ). Similar investigations with chemically more complex polymers are exceedingly difficult, and healing of polymers containing dynamic bonds is therefore typically probed by macroscopic experiments, such as the qualitative observation of the disappearance of scratches ( 3 , 4 , 21 ), or by comparing the mechanical properties of damaged and healed samples ( 14 – 18 , 22 ). For example, the recovery of the elongation at break, tensile strength, and/or toughness is established by tensile tests ( 14 , 21 , 23 – 25 ) or fracture mechanics ( 26 – 28 ).…”

Towards photoswitchable quadruple hydrogen bonds via a reversible “photolocking” strategy for photocontrolled self-assembly

“…Beneting from the dynamic nature, good directionality, versatility and high stability, multiple H-bonded motifs have been integrated into the polymeric scaffolds to fabricate H-bond cross-linked polymeric materials with tunable microstructures and high-performances. [75][76][77][78][79][80][81][82] To further apply Azo-UPy for the construction of photocontrollable macromolecular systems, a linear polymer Azo-UPy-P was then synthesized, with the side chains being modied with Azo-UPy (Fig. 3a).…”