Versatile tensile and fracture behaviors of dual cross-linked elastomers by postpreparation photo tuning of local cross-link density

This study demonstrates the postpreparation easy tuning of the Young's modulus of elastomers by using polyesters bearing thermal and photo cross-linkable groups. In the first cross-linking step, only thermoreactive groups form cross-links, resulting in a highly deformable soft elastomer. In the second step, photoreactive groups are cross-linked by UV irradiation, and controlling the UV irradiation time can tune the cross-link density, resulting in modulus tuning over two orders of magnitude at room temperature. The use of photo reaction enables precise modulus patterning using photomasks with a series of slits. In horizontally patterned samples, the dually cross-linked stiff section shows negligible deformation, whereas large elongation is observed selectively in the single cross-liked soft sections. In vertically patterned samples, interestingly, crack propagation and complete fracture are significantly suppressed, compared with the fully dually cross-linked sample. The present data can thus provide important insight for developing new methodologies for controlling the tensile and fracture behavior of elastomers. [Display omitted] •Synthesis of amorphous polyesters with dual cross-linkable moieties.•Wide range modulus tuning via two step postpreparation approach.•Variation of tensile and fracture behaviors by local modulus photo-patterning.