Revolutionizing High-Temperature Electrical Properties of Epoxy Resin via Tailoring Weak Conjugation Rigid Structures.

The escalating demand for high-power and compact-size advanced electronic devices and power systems necessitates polymers to exhibit superior electrical properties even under harsh environments. However, reconciling the seemingly contradictory attributes of excellent electrical properties and thermal stability poses a formidable challenge for current epoxy polymer (EP) materials and their applications. To meet the need, here two classes of bi-aryl diamine curing agents are described that enable polymers to exhibit well-balanced thermal and dielectric properties with functional bridging groups. A weak conjugation system in highly thermally stable polymers with an aromatic backbone is constructed, using electron-modulating bridging groups to immobilize intramolecular free carriers by tailoring trap sites, and bulky bridging groups to prevent molecular stacking to inhibit intermolecular charge transport. The resultant polymer exhibits a volume resistance of 7.45 × 10¹² Ω m and a direct current breakdown strength of 368.74 kV mm^-1 at 120 °C, which are 2.2 and 2.4 times higher than that of commercial anhydride-cured EP, respectively. It is demonstrated to be due to the inhibition of charge injection and transport. The proposed aromatic amine multimolecule approach, combined with diverse functional bridging groups, is a promising direction for exploring next-generation EP insulation materials suitable for extreme conditions.