An Interfacial Dynamic Crosslinking Approach toward Catalyst-free and Mechanically Robust Elastomeric Vitrimer with a Segregated Structure

Elastomeric vitrimers with covalent adaptable networks are promising candidates to overcome the intrinsic drawbacks of conventional covalently-crosslinked elastomers; however, most elastomeric vitrimers show poor mechanical properties and require the addition of exogenous catalysts. Herein, we fabricate a catalyst-free and mechanically robust elastomeric vitrimer by constructing a segregated structure of sodium alginate (SA) in the continuous matrix of epoxidized natural rubber (ENR), and further crosslinking the composite by exchangeable hydroxyl ester bonds at the ENR-SA interfaces. The manufacturing process of the elastomeric vitrimer is facile and environmentally friendly without hazardous solvents or exogenous catalysts, as the abundant hydroxyl groups of the segregated SA phase can act as catalyst to activate the crosslinking reaction and promote the dynamic transesterification reaction. Interestingly, the segregated SA structure bears most of the load owing to its high modulus and small deformability, and thus ruptures preferentially upon deformation, leading to efficient energy dissipation. Moreover, the periodic stiffness fluctuation between rigid segregated SA phase and soft ENR matrix is beneficial to the crack-resisting. As a result, the elastomeric vitrimer manifests exceptional combination of catalyst-free, defect-tolerance, high tensile strength and toughness. In addition, the elastomeric vitrimer also exhibits multi-shape memory behavior which may further broaden its applications.