Gradient distribution of trap states in polymer dielectrics induced by electric field for enhanced insulation properties

The insulating performance of polymer dielectrics is crucial for the stable operation of electronic and electrical equipment, with trap states being an important indicator of charging and discharging processes. However, most of existing modification methods regulate trap states by greatly changing the original material system or introducing foreign component. In this study, we proposed the idea of tailoring the trap states by controlling the density of unreacted radicals, which can be readily realized by changing the content of catalysts. On this basis, functional graded materials (FGM) with gradient trap distributions were fabricated by an electric field-induced molecular self-assembly technique. It was found that deep traps were produced by the free radicals of unreacted groups, which can be created by incomplete curing process and overly rapid reaction rate in the case of insufficient and excessive catalysts respectively. Moreover, the in-situ electric field drives the directional migration of protonated [DMP-30H]⁺ molecules, successfully creating a FGM material with gradient distribution of accelerator concentrations, regulating the local trap characteristics and resulting in a “medium-high-low” conductivity spatial distribution pattern. The FGM spacer made the surface charges accumulate on the middle right region in the spacers, which effectively suppresses electric field distortion at the triple junction, resulting in a 24.35 % improvement in flashover voltage compared to the homogeneous material. The study provides a new approach for tailoring the trap distribution of polymers to achieve outstanding insulation properties.