Electrical and dielectric properties of poly(1,3,4-oxdiazole) nanocomposite films with graphene sheets dispersed in layers

Abstract

Electrical and dielectric measurements over a broad frequency range from 20 Hz to 2 MHz were carried out for a series of sulfonated poly(1,3,4-oxadiazole) (sPOD) nanocomposite films containing exfoliated graphene sheets of 0.1-10.0 wt%, which were manufactured via ultrasonication-based solution mixing and casting method. TEM and XRD data revealed that the graphene sheets were dispersed by forming a layered structure in the nanocomposite films with >2.0 wt% graphene. The frequency-dependent electrical conductivity and relative permittivity of the nanocomposite films were dependent on the graphene content. The neat sPOD and its nanocomposites with lower graphene contents of 0.1-2.0 wt% exhibited low electrical conductivity of ~10-13-10-12 S/cm and relative permittivity of 1.7-6.6 at 20 Hz. In cases of the nanocomposite films with high graphene contents of 5.0 and 10.0 wt%, highly improved relative permittivity of ~101 and ~560 at 20 Hz as well as electrical conductivity of ~10-9 S/cm and ~10-6 S/cm was attained at 20 Hz, respectively. In addition, the nanocomposite films with 5.0 and 10.0 wt% exhibited relatively high capacitance of ~39.7 pF and ~75.5 pF at 20 Hz, respectively. The highly enhanced relative permittivity and capacitance for the nanocomposite films with 5.0-10.0 wt% graphene was interpreted to be owing to the accumulation of electronic charges at the interfaces between insulating sPOD matrix and conductive graphene sheets dispersed in layers.