Self-Healing of Electrical Damage in Microphase-Separated Polyurethane Elastomers with Robust Dielectric Strength Utilizing Dynamic Hydrogen Bonding Networks

Polymer dielectrics are predominantly used as primary insulating materials in various electrical and electronic systems. Recently, self-healing dielectrics have been designed to heal microdamage in polymers to repair discharge channels and restore their critical insulating properties. However, the low dielectric strength of extrinsic self-healing polymers is a critical disadvantage in preventing them from practical application. In this work, we designed and implemented an insulating robust self-healing polyurethane (PU) utilizing a microphase-separating structure with a shape memory effect. The microphase separation structure in the PUs allows hard segments (HSs) to provide high dielectric strength while achieving self-healing through the soft segments (SSs) with high flowability. The analysis of dielectric relaxation behavior and quantum chemical calculations in combination indicated that the energy barrier at the interface of SS and HS is the key factor in improving the dielectric strength of polyurethanes. Observations from three-dimensional computed micro-X-ray tomography and optical microscopy showed that the PU developed can fully heal the damaged area under moderate thermal stimulation while restoring its electrical performance. The calculation of conformational entropy and the verification of the reversibility of hydrogen bonds further illustrated the reason for efficient self-healing capability of the designed PU. This work opened up opportunities for reliable applications of self-healing dielectrics in electrical and electronic apparatus.