Dilute Nanocomposites: Tuning Polymer Chain Local Nanostructures to Enhance Dielectric Responses.

Dielectric polymers possessing high energy and low losses are of great interest for electronic and electric devices and systems. Nanocomposites in which high dielectric constant (high-K) nanofillers at high loading (>10 vol%) are admixed with polymer matrix have been investigated for decades, aiming at enhancing the dielectric performance, but with limited success. In 2017, it is discovered that reducing nanofiller loading to less than 0.5 vol% in polymer matrix can lead to marked enhancement in dielectric performance. Here, we reviewed the discoveries and advances of this unconventional approach to enhance dielectric performance of polymers. Experimental studies uncover that nanofillers lead to interfaces changes over distances larger than 100 nm. Experimental and modeling results show that introducing free volume in polymers reduces the constraints of glass matrix on dipoles in polymers, leading to enhanced K without affecting breakdown. Moreover, low-K nanofillers at low-volume loading serve as deep traps for charges, lowering conduction losses and increasing breakdown strength. The dilute nanocomposites provide new avenues for designing dielectric polymers with high K, minimal losses, and robust breakdown fields, thus achieving high energy and power density and low loss for operation over a broad temperature regime.