Self-Healing of a Cross-Linked Polymer with Dynamic Covalent Linkages at Mild Temperature and Evaluation at Macroscopic and Molecular Levels

Abstract

A lot of self-healing materials using dynamic bonding systems have been reported, while the focus is mainly on the macroscopic self-healing behavior such as visually recognizable healing. Because the healing originates from microscopic chemical reactions of the dynamic bonds, evaluation of the reactions in the materials is necessary for elucidation of the healing mechanisms and development of the healing ability. Herein, we demonstrated self-healing of a cross-linked polymer with diarylbibenzofuranone (DABBF)-based dynamic covalent linkages at mild temperature and investigated the healing behavior from both macroscopic and microscopic viewpoints. The macroscopic behavior was inspected by mechanical tests, and the linkage reaction (equilibrium) was evaluated by electron paramagnetic resonance measurements. These assessments revealed that the healing is strongly dependent on temperature, which is attributable to synergism between changes in the chain mobility and in the equilibrium of the incorporated linkages. These findings would be applicable to other dynamic bonding systems.