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.

Hot melt adhesives are widely applied owing to their solvent-free nature. Developing robust and multi-reusable hot melt adhesives without harsh bonding conditions remains a great challenge. Herein, we develop a novel strategy of incorporating flexible side chains into the network of highly noncovalently cross-linked hot melt adhesives to construct super strong and multi-reusable supramolecular epoxy hot melt adhesives (SEA). The SEA was prepared via polycondensation of diglycidyl ether of bisphenol A with O-(2-ureido-4[1H]pyrimidinone)-O′-(2-aminopropyl)polypropylene glycol (the noncovalent cross-linker) and O-(2-aminopropyl)-O′-(2methoxyethyl)polypropylene glycol (the flexible side chain). Impressively, the prepared SEA was endowed with a super high adhesion strength of 10.2 MPa, which is the highest adhesion strength in bonding stainless steel among hot melt adhesives constructed by dynamic bonds to the best of our knowledge. It also featured excellent multiple reusability with more than 80% of the original adhesion strength remained even after reuse for six times. Meanwhile, the SEA displayed an outstanding ability to bond diverse substrates tightly under considerably moderate bonding conditions (80 °C for 5 min). It is highly anticipated that this work will open a new avenue of designing hot melt adhesives with the high adhesion strength and excellent multiple reusability.

Recycling of discarded polyethylene terephthalate (PET) is an important issue for both environmental protection and resource conservation purposes. In this work, a dissolution-degradation strategy has been developed for recycling PET by adding solvents such as aniline, nitrobenzene, 1-methyl-2-pyrrolidinone (NMP), or dimethyl sulfoxide (DMSO) into the traditional PET glycolysis system. The results show that the conversion of PET reaches 100% and the yield of monomer bis(hydroxyalkyl) terephthalate (BHET) reaches 82% during 1 min with zinc acetate as catalyst in DMSO at 463 K. Importantly, this strategy can be applied to a variety of catalysts. The simulation and in situ IR results indicate that the π−π interaction between PET and aromatic solvents plays a key role in PET dissolution, which leads to fast degradation. This promising dissolution-degradation strategy can improve the glycolysis efficiency of PET dramatically and may be applied to the degradation process of other polyesters.

Developing high-performance and reusable adhesives from renewable feedstocks is of significance to sustainable development, yet it still remains a formidable task. Herein, castor oil, melevodopa, and iron ions are used as building blocks to construct a novel bio-based supramolecular adhesive (BSA) with outstanding adhesion performances. It is prepared through partial coordination between melevodopa functionalized castor oil and Fe 3+ ions. Noncovalent interactions between adherends and the catechol unit from melevodopa contribute to reinforcing adhesion, and the metal-ligand coordination between catechol and Fe 3+ ions is utilized to strengthen cohesion. By combining strong adhesion and tough cohesion, the prepared BSA achieves an adhesion strength of 14.6 MPa at ambient temperature, a record-high value among reported bio-based adhesives as well as supramolecular adhesives to the best of knowledge. It also outperforms those adhesives at cryogenic temperature, realizing another record-high adhesion strength of 9.5 MPa at −196 °C. In addition, the BSA displays excellent multi-reusability with more than 87% of the original adhesion strength remaining even after reuse for ten times. It is highly anticipated that this line of research will provide a new insight into designing bio-based adhesives with outstanding adhesion performances and excellent multi-reusability.

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