In situ vitamin C reduction of graphene oxide for preparing flexible TPU nanocomposites with high dielectric permittivity and low dielectric loss

Flexible thermoplastic polyurethane/reduced graphene oxide (TPU/rGO) nanocomposite sheets were prepared via a combination of solvent-exchange and in situ vitamin C reduction. Raman, Fourier transform infrared and X-ray photoelectron spectroscopy suggest a successful reduction of the GO by vitamin C, which largely enhances the interfacial polarization ability of the resultant rGO layers. Hence, the TPU/rGO sheets exhibit much higher dielectric permittivity (ε′) than corresponding TPU/GO sheet. X-ray diffraction patterns, transmission electron microscopy image and predicated rGO layer thickness all indicate good exfoliation and dispersion of the rGO layers in the TPU matrix. Rheological tests demonstrate that a percolation structure is formed in the nanocomposite with 0.75 vol% rGO. The enhanced interfacial polarization ability and possible formation of micro-capacitor network of the rGO layers result in high ε′ (151 at 1 kHz) for the nanocomposite sample with only 0.75 vol% rGO. Meanwhile, its dielectric loss remains lower than 1 at 1 kHz, which can be attributed to weakened tunnel current between two adjacent rGO layers by the insulating TPU barriers in between.