Fabrication of Recyclable Polyurethane Elastomers with Excellent Mechanical and Creep-Resistant Properties Based on a Bio-Sourced Azine Chain Extender

Dynamic covalent polymers (DCPs) have attracted extensive attention as they integrate the advantages of thermoset and thermoplastic resins. However, the heat resistance was compromised due to the unstable features of dynamic covalent bonds. Therefore, it is still a challenge to develop DCPs possessing excellent heat resistance and recycling properties at the same time. Moreover, production and employment of biomass-derived chemicals have become increasingly urgent due to the petroleum shortage and environmental problems. Herein, a biomass-sourced azine chain extender was synthesized from biomass platform compound, 5-hydroxymethylfurfural. Small-molecule model furan azine compounds were synthesized to investigate the exchange mechanism at a high temperature. A series of azine polyurethane elastomers were prepared, containing different ratios of furan azine chain extenders. The synthesized furan azine polyurethane elastomers (FAPUEs-3) exhibited excellent mechanical properties compared with the control sample (FAPUEs-3CS), probably owing to the rigidity and polarity of furan rings. The obtained FAPUEs also showed excellent creep resistance at high temperatures by virtue of high exchange temperatures of furan azine moieties. The FAPUEs can be easily degraded under acidic conditions in acetone. The recovery rate of tensile strength could be still above 90% after 3 recycles at 150 degrees C under a pressure of 10 MPa. FAPUEs also showed excellent antibacterial effects against E. coli and S. aureus as azine moieties are a special kind of Schiff base. The FAPUEs opened an avenue for developing biomass-sourced recyclable PUEs.