Interface design for synergistic improvement of the thermal conductivity and dielectric properties of dielectrics is urgently needed but still challenging for the next generation of electronic and electrical equipment development. Herein

the authors report a strategy to screen structural units for the interface design of polymer dielectrics working under high-frequency and high-voltage conditions. Thermal conductivity

dielectric loss

the highest occupied molecular orbital (HOMO) and the lowest unoccupied molecular orbital (LUMO) gap are employed as key parameters to be considered simultaneously in the interface design for the screening. The authors find that a rigid ring with hydroxyl groups at symmetric sites can suppress the steric hindrance of neighbouring hydrogen bonds

leading to a better phonon spectrum matching and more efficient suppression of molecular chain segment motion

which ensures the dielectric insulating performance and thermal conduction performance simultaneously. Typically

alkyl polyglucoside (APG) was selected as the optimal modifier to demonstrate the interface designing principle experimentally

exhibiting improved thermal conductivity and suppressed dielectric loss

ultimately resulting in a 4.98-fold increase in the high-frequency breakdown time. This study provides important insights into decisive structural factors necessary to achieve dielectrics with excellent insulating properties under high-frequency applications.