Epoxy-Based Catalyst-Free Self-Healing Elastomers at Room Temperature Employing Aromatic Disulfide and Hydrogen Bonds

In this paper, catalyst-free room-temperature healing epoxy vitrimer-like materials (S-vitrimer) are introduced. The S-vitrimer can be healed at room temperature without any external stimuli such as solvent, pressure, heat, and catalyst through an aromatic disulfide exchange reaction and a hydrogen bond because the glass transition temperature of the S-vitrimer is lower than room temperature. Self-healing materials are attracting widespread attention nowadays with their potential to increase the durability of the materials. However, there is still elevating need for research, considering the limitations of various self-healing methods. To the best of our knowledge, epoxy-based catalyst-free room-temperature healing materials have not been investigated until now, yet they are promising to make self-healing easier. Moreover, the S-vitrimer showed higher healing efficiency when healed for a longer time and at a higher temperature. Especially when healed at room temperature for 96 h, the S-vitrimer presented an 80% healing efficiency. The S-vitrimer also showed an 80% healing efficiency when healed at 60 °C for 48 h. To investigate the factors affecting self-healing behavior, three control experiments were carried out. Control experiments showed that the S-vitrimer is healed mainly due to a disulfide exchange reaction, but hydrogen bonds also contribute to self-healing behavior. Also, it was found that tightly packed segments can hinder self-healing through control experiments.