Toughening 3D printed elastomers using mechanophore crosslinkers

Elastomeric materials are widely used in industrial application sectors including construction, automotives, soft robotics, and biomedicine. Light-based three-dimensional (3D) printing enables the manufacturing of elastomeric polymer networks with geometric and functional customizability beyond the capabilities of traditional manufacturing methods. These 3D printed polymer networks often suffer from premature mechanical failure of the material that limits their viability in load-bearing applications. One approach to toughen elastomers is to employ non-covalent additives as sacrificial bonds in the polymer network; however, this toughness enhancement comes with a trade-off in the stiffness of the resultant object. Herein, we use a 1 : 1 substitution of cyclobutane-based mechanophores as scissile covalent crosslinks in 3D printed poly(methoxyethylacrylate) networks to enhance the material toughness without compromising stiffness. These crosslinkers increased the material's toughness in tensile and tearing tests without altering its stiffness or appearance. The enhanced toughness and tear resistance of these elastomers enabled bonding operations such as stitching and suturing. The results suggest that mechanophores offer a promising route to toughen 3D printed elastomers.