Crystalline properties, dielectric response and thermal stability of in-situ reduced graphene oxide/poly(vinylidene fluoride) nanocomposites

Graphene oxide nanosheets (GOn)/poly(vinylidene fluoride)(PVDF) nanocomposites were fabricated using solution mixing followed by hot press molding and solution casting respectively. The GOn were homogeneously dispersed and distributed within the PVDF matrix, which resulted in the formation of a purely β-polymorph at only 0.05 wt.% GOn loading in the solution casted composites. A gradual crystal transformation of PVDF from α-phase structure into β-phase was observed in the hot pressed composites. The GOn in nanocomposites were confirmed to be partially reduced in-situ during hot press molding performed at 180 °C for 8 min. Due to the high compatibility between GOn and PVDF, the in-situ reduced GOn/PVDF nanocomposites showed an insulator-to-conductor transition with a low percolation threshold of nearly 0.5 wt.%. For the in-situ reduced GOn/PVDF nanocomposites, the addition of 1.5 wt.% GOn loading induced an increase of over 14 °C in the maximum degradation temperature of PVDF.