Itaconic acid-based sustainable polyurethane covalent adaptable networks with robust mechanical, reshaping and UV-resistant properties based on reversible disulfide bond

Thermoset polymer materials are widely used in various fields due to their excellent performance brought by their permanently cross-linked structures. However, their inability to be recycled also leads to a serious waste of resources. The emergence of covalent adaptable networks (CANs) has solved the problem perfectly that thermoset materials are difficult to recycle. Meanwhile, with the increasing concern for resources and the environment, bio-based materials have sparked a research boom. Itaconic acid is a biomass feedstock with great prospects for development. In this study, itaconic acid, 1,6-hexanediol, 6-mercapto-1-hexanol, isocyanate, and 4,4′-dithiodiphenylamine were used as raw materials. Itaconic acid-based polyols were first synthesized by thiol-ene click reaction, and a series of itaconic acid-based polyurethane (PU) materials containing dynamic covalent networks were synthesized by varying the ratios between the amino and hydroxyl groups. The obtained material has good mechanical properties with a maximum tensile strength of 31.5 MPa and a modulus of 717 MPa. The presence of disulfide bonds allows the material to be recycled by remodeling, and the recovery efficiency of tensile strength after three remodeling cycles is 85.1 %. The material also has excellent solvent resistance and UV-blocking resistance. In conclusion, this work provides possible ideas for the high-value utilization of itaconic acid in polyurethanes.