Electrical and Dielectric Properties of Poly(1,3,4-oxdiazole) Nanocomposite Films with Graphene Sheets Dispersed in Layers

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 similar to 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 similar to 101 and similar to 560 at 20 Hz as well as electrical conductivity of similar to 10(-9) S/cm and similar to 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 similar to 39.7 pF and similar to 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.