This study presents a method to enhance the mechanical properties of unfilled elastomers by introducing sacrificial bonds that break and dissipate energy before the material fails. The researchers used a combination of sequential free-radical polymerizations to create double (DN) and triple (TN) network elastomers. These networks consist of isotropically prestretched chains that can break, allowing the material to absorb more energy and become tougher. The sacrificial bonds are monitored in real time using chemoluminescent cross-linking molecules that emit light when they break, providing a map of where and when the bonds break during crack propagation. The elastomers were synthesized by first creating a well-cross-linked rubbery network through UV polymerization. This network was then swollen with a second monomer, UV initiator, and a small amount of cross-linker, effectively isotropically stretching the chains. A second UV polymerization was performed on this swollen network until all monomers were consumed. The degree of cross-linking in the first network controlled the level of swelling and the prestretch of the chains. Repeating this process allowed for even lower-volume fractions of the first network and higher levels of prestretch. The mechanical properties of the elastomers were evaluated through stress-strain tests, showing a significant increase in elastic modulus and true stress at break. The fracture toughness, measured as the critical energy release rate $ G_c $, increased substantially, reaching values comparable to some filled elastomers or the best tough hydrogels. The study also demonstrated that the fracture toughness is influenced by the dissipation of energy due to the breakage of sacrificial bonds in the material. The chemoluminescent cross-linker, BADOBA, was used to visualize the breakage of sacrificial bonds during deformation. The light emitted when the bonds break provided a real-time map of where and when the bonds break, showing that the damage is localized near the crack tip. This information helps in understanding the fracture mechanism and can guide the design of new materials with improved mechanical properties. The results indicate that the toughening mechanism relies on the dissipation of energy through the breakage of a variable fraction of sacrificial prestretched chains, allowing for the development of tough, stiff unfilled elastomers with minimal residual deformation and negligible viscoelasticity. The methodology can be used to develop better models of fracture in soft materials and to guide the design of other families of soft materials.This study presents a method to enhance the mechanical properties of unfilled elastomers by introducing sacrificial bonds that break and dissipate energy before the material fails. The researchers used a combination of sequential free-radical polymerizations to create double (DN) and triple (TN) network elastomers. These networks consist of isotropically prestretched chains that can break, allowing the material to absorb more energy and become tougher. The sacrificial bonds are monitored in real time using chemoluminescent cross-linking molecules that emit light when they break, providing a map of where and when the bonds break during crack propagation. The elastomers were synthesized by first creating a well-cross-linked rubbery network through UV polymerization. This network was then swollen with a second monomer, UV initiator, and a small amount of cross-linker, effectively isotropically stretching the chains. A second UV polymerization was performed on this swollen network until all monomers were consumed. The degree of cross-linking in the first network controlled the level of swelling and the prestretch of the chains. Repeating this process allowed for even lower-volume fractions of the first network and higher levels of prestretch. The mechanical properties of the elastomers were evaluated through stress-strain tests, showing a significant increase in elastic modulus and true stress at break. The fracture toughness, measured as the critical energy release rate $ G_c $, increased substantially, reaching values comparable to some filled elastomers or the best tough hydrogels. The study also demonstrated that the fracture toughness is influenced by the dissipation of energy due to the breakage of sacrificial bonds in the material. The chemoluminescent cross-linker, BADOBA, was used to visualize the breakage of sacrificial bonds during deformation. The light emitted when the bonds break provided a real-time map of where and when the bonds break, showing that the damage is localized near the crack tip. This information helps in understanding the fracture mechanism and can guide the design of new materials with improved mechanical properties. The results indicate that the toughening mechanism relies on the dissipation of energy through the breakage of a variable fraction of sacrificial prestretched chains, allowing for the development of tough, stiff unfilled elastomers with minimal residual deformation and negligible viscoelasticity. The methodology can be used to develop better models of fracture in soft materials and to guide the design of other families of soft materials.