Reinforcement of boron–nitrogen coordinated polyurethane elastomers with silica nanoparticles

Polyurethane elastomer nanocomposites are strategically important due to their indispensable applications in daily life and high-tech fields. Herein, a series of nanocomposites with extraordinary strength, toughness and energy dissipation are reported, which are enabled by multiple dynamic moieties including dynamic boronic ester covalent bonds, boron-nitrogen coordination bonds in the matrix and on the interface. The surface-modified silica nanoparticles with amino-silane coupling agent (D-SiO2) were added to the polyurethane matrix that contains boron-nitrogen coordination. The presence of interfacial coordination significantly improves the dispersion of D-SiO2 and enhances the interface interaction of polyurethane composites (SPU/D-SiO2), which is evidenced by scanning electron microscopy, transmission electron microscopy and rheological investigation. Through mechanical experiment analysis, these modified polyurethane composites exhibit high tensile strength and toughness. The tensile strength of SPU/10D-SiO2 increases to 19.5 ± 0.2 MPa and its tensile toughness achieves 216.9 MJ/m3, which is 35% of increase as compared with the pristine SPU that had a record-high toughness. In addition, the coordination bonds in the matrix and interface in the composites provide versatile and efficient energy dissipation during the tensile process. This work offers a facile method to improve the mechanical robustness of the newly developed supramolecular polyurethane elastomers.