High-strength supramolecular covalent adaptable networks with reprocessability and closed-loop recyclability

The widespread use of and extreme difficulty in degradation of plastics have brought enormous pressure to ecosystems, and it is crucial to develop materials that can undergo chemical recycled under moderate conditions and at the same time possess mechanical properties comparable to traditional plastics. Herein, a supramolecular covalent adaptable network (sCAN-Ht) for chemically closed-loop recycling at room temperature was designed and synthesised using tris(6-(4-formyl- 2-methoxyphenoxy) hexyl)((2,4,6-trioxo-1,3,5-triazinane-1,3,5-triyl) tris(hexane-6,1- diyl)) tricarbamate (TPAU-Ht) and tris(2-dimethylaminoethyl)amine (TREN) through a Schiff-base reaction between amine and aldehyde groups. Significant modulation of the mechanical properties could be achieved by introducing different ratios of aldehyde and amino groups into the polymer. As the ratio of aldehyde to amino group increased, the tensile strength of sCAN-Ht- x initially increased and then decreased. The sCAN-Ht-2 exhibited a Young's modulus of 1221 ± 43 MPa, tensile strength of 67.5 ± 7 MPa, and an elongation at break of 101.1 ± 10 %. sCAN-Ht demonstrates the reprocessing characteristics of a thermoplastic and at the same time exhibits solvent resistance similar to that of a thermoset. It can also be recovered in a closed-loop manner under acidic conditions, with 77 % recovery of monomer and 74 % recovery of TREN, which can be used to regenerate sCAN-Ht without compromising mechanical performance. sCAN-Ht provides a favourable development direction for solving the problem of plastics degradation due to its excellent mechanical, solvent-resistant, reprocessing, and recyclable properties.