Effect of processing method on the dielectric behavior of graphene oxide/PVDF nanocomposites

Graphene oxide nanosheets (GOn)/PVDF nanocomposites with various GOn contents were fabricated using solution mixing followed by hot press molding and solution casting respectively. The dielectric behavior of those nanocomposites was determined over a wide frequency range from 102 to 107 Hz. The percolation phenomenon was observed in GOn/PVDF nanocomposites prepared by hot press molding method instead of solution casting method. It indicates that the GOn in nanocomposites were partially reduced in-situ under the molding conditions (180 °C, 8 min). And a percolation threshold of nearly 0.5 wt% was achieved by the homogeneous dispersion and distribution of GOn within the matrix due to the strong and specific interaction between carbonyl group in GOn surface and fluorine group in PVDF, which is lower than that of graphene sheets (GSs)/PVDF nanocomposites reported. The dielectric permittivity of in-situ reduced GOn/PVDF nanocomposites was found to increase with increasing GOn contents, while the dielectric permittivity of samples by solution casting with GOn contents lower than 1 wt% was found to be lower than that of pure PVDF. The gradual crystal transformation of PVDF from α-phase structure into β-phase with increasing GOn contents was observed in the in-situ reduced GOn/PVDF nanocomposites, which also confirms the destruction of oxygen-containning groups in GOn surface due to the thermal stress in sample preparation.