Endowing smart self-reporting epoxy composites with superior electrical properties from ultralow-content electron-donating encapsulated microsensors

Abstract

Smart self-reporting dielectrics (SRDs) have been extensively utilized for intelligentizing and miniaturizing next-generation advanced electrical and electronic devices. However, switchable structures towards the self-reporting function commonly damage electrical properties, severely undermining the reliability and practicality of SRDs. Herein, the smart self-reporting function and superior electrical properties are simultaneously achieved by incorporating ultralow content microsensors with electron-donating encapsulation into the epoxy matrix. The microsensor is a leuco dye system for self-reporting temperature anomalies through thermochromism. The strong electron-donating melamine–formaldehyde encapsulation of microsensors serves to confine the switchable structures and enhance electrical properties by constructing the interfacial barrier effect through triboelectrification. Under an ultralow doping content of 0.5 phr, the electrical conductivity of SRDs is considerably reduced by about 80% at the elevated temperature of 80 °C compared to that of the widely recognized epoxy insulation. The reduction efficiency is far superior to those of numerous micro- and nanofillers. The interfacial barrier effect can be supported by the significantly reduced trapped charge density and trap levels in SRDs based on thermal stimulated depolarization current results. Consequently, the charge injection and transport in SRDs can be distinctly inhibited, realizing the enhancement of electrical properties. The results of this study could provide a facile and efficient strategy for achieving high-performance SRDs, which is appealing and vital for widespread applications of SRDs.