Interplay between Thermal Denaturation and Dynamic Covalent Chemistry Generates High-Performance Recyclable Protein Plastics.

Chemically recyclable and/or biobased polymers are promising alternatives to conventional petroleum-derived plastics, yet strategies that simultaneously improve their performance and recyclability remain scarce. Here, we report that the combined use of thermal denaturation and dynamic covalent chemistry can transform protein materials into strong, chemically recyclable bioplastics with enhanced hydrolytic stability. Cross-linking a priori brittle bovine serum albumin (BSA) with dynamic vinylogous urethane (VU) linkages produces robust plastics with tensile strengths of up to 35 MPa. Simultaneously, thermal denaturation at 80 °C restructures BSA from α-helices into more hydrophobic β-sheet-rich domains, reducing water absorption and thereby stabilizing the otherwise hydrolyzable VU cross-links. The resulting protein networks are chemically recyclable in acidic water, allowing the recovery of both BSA and cross-linkers. Overall, by exploiting the reciprocal interplay between dynamic covalent cross-linking and protein thermal denaturation, this work offers a fresh perspective to overcome the trade-off between polymer stability and recyclability.