Nano-scale insulation effect of polypyrrole/polyimide core–shell nanoparticles for dielectric composites

The core–shell polypyrrole@polyimde (PPy@PI) particles were prepared and investigated on their dielectric properties for all-organic dielectric composites. The individually insulated PPy nano particles were formed by nano-scale coatings, which were obtained through interfacial precipitation, where the negatively charged polyamic acid (PAA) interact and are precipitated on the positively charged PPy particles. PAA shell becomes PI shell on PPy particles to form PPy@PI core–shell via imidization. The core–shell structure of PPy@PAA was observed by transmission electron microscopy (TEM) with staining of particles. At the 15 wt% PPy in PPy@PI composite, the dielectric permittivity of over 100 was obtained with the electrical conductivity of 10−8 S/cm. High fractional use of PPy in dielectric layer as over 30 wt% PPy gave the ultra-high dielectric permittivity of 487. The loss tangent of PPy@PI is lower than 0.18 until 15 wt% PPy content.