Highly Stretchable And Strong Poly(Butylene Maleate) Elastomers Via Metal-Ligand Interactions

The search for advanced elastomers with simultaneously high strength, high stretchability and reprocessability remains a challenging task. Herein, we report an innovative method to prepare high-performance yet reprocessable poly(butylene maleate) (PBM) elastomers by forming dynamic metal-ligand (M-L) crosslinks among PBM chains. 2-Pyrazine ethanethiol, a commercially available food flavor, was used to introduce pyrazine ligands on PBM chains by the thiol-ene click reaction. A series of metal salts with different metal ion valences, counteranions and metal types were used to form metal-pyrazine interactions, showing that all three factors affect the M-L bond strength and thus the mechanical behavior of the crosslinked PBM elastomers. A tensile strength as high as 4 MPa and elongation at break up to 1630% were achieved for the Fe(BF4)(2)-crosslinked PBM elastomer, which were 1 and 22 times better than those of a covalently crosslinked PBM elastomer, and the dynamically crosslinked PBM elastomer can be reprocessed at 100 degrees C by hot pressing. This excellent recyclability was attributed to the dynamic nature of M-L bonds. During tensile testing, some of the M-L bonds were reversibly broken and reformed to release two types of coiled segments and enable the chain sliding, resulting in high extensibility; in the meantime, the M-L interactions and the network structure were optimized when the molecular chains were gradually oriented along the pulling direction, ensuring high strength. The designed M-L crosslinked PBMs are promising candidates for advanced elastomers with highly tunable mechanical properties.