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 primaryinsulatingmaterials in various electrical and electronic systems. Recently,self-healing dielectrics have been designed to heal microdamage inpolymers to repair discharge channels and restore their critical insulatingproperties. However, the low dielectric strength of extrinsic self-healingpolymers is a critical disadvantage in preventing them from practicalapplication. In this work, we designed and implemented an insulatingrobust self-healing polyurethane (PU) utilizing a microphase-separatingstructure with a shape memory effect. The microphase separation structurein the PUs allows hard segments (HSs) to provide high dielectric strengthwhile achieving self-healing through the soft segments (SSs) withhigh flowability. The analysis of dielectric relaxation behavior andquantum chemical calculations in combination indicated that the energybarrier at the interface of SS and HS is the key factor in improvingthe dielectric strength of polyurethanes. Observations from three-dimensionalcomputed micro-X-ray tomography and optical microscopy showed thatthe PU developed can fully heal the damaged area under moderate thermalstimulation while restoring its electrical performance. The calculationof conformational entropy and the verification of the reversibilityof hydrogen bonds further illustrated the reason for efficient self-healingcapability of the designed PU. This work opened up opportunities forreliable applications of self-healing dielectrics in electrical andelectronic apparatus.