Self-Healing Properties of ESOF-Ix Material: Investigation of Diels-Alder Bond-Mediated Repair

The deterioration of adhesive performance is often a consequence of internal crack formation. Due to the challenges associated with timely detection and repair of micro-cracks, material mechanical performance is compromised, leading to reduced service life and limited application range. Consequently, timely crack repair, particularly through the implementation of self-healing mechanisms, is of paramount importance for enhancing material utilization efficiency. The concept of self-healing materials draws inspiration from the natural healing processes observed in biological skin, where repair agents stored within the material are released and polymerized or reversible interactions within the material are reformed. These materials exhibit the ability to perceive changes in the external environment and respond accordingly, ultimately restoring their original performance. Self-healing materials can be broadly classified into two categories: exogenous and intrinsic.

Exogenous self-healing involves incorporating composite functional substances into the material, such as microcapsules containing monomers. Upon material damage, cracks propagate and trigger the release of monomers, which subsequently polymerize and repair the damage. However, this method is inherently limited by the finite supply of repair agents. Intrinsic self-healing, on the other hand, relies on providing energy to the material to enable covalent or non-covalent interactions within the material itself. This approach introduces dynamic characteristics and environmental responsiveness, enabling multiple self-healing cycles. ESOF-Ix, due to the incorporation of Diels-Alder bonds, exhibits the characteristics of intrinsic self-healing materials.

To evaluate the self-healing capability of ESOF-Ix, ESOF-I1.0 was selected as a representative case and intentionally scratched to create a surface crack. Subsequently, the material was subjected to heating at 130℃ for varying durations. As depicted in Figure 5, the crack gradually diminished with increasing heating time, demonstrating exceptional self-healing performance. This phenomenon can be attributed to the dissociation of Diels-Alder bonds at elevated temperatures. This disruption of the cross-linked network structure enhances the mobility of the polymer chains, allowing them to migrate between the two interfaces of the scratch. Upon cooling, the Diels-Alder bonds reform, leading to the reconstruction of the cross-linked network structure and ultimately resulting in the repair of the scratch.