Graphene is widely used in heat dissipation, owing to its inherently high in-plane thermal conductivity and excellent mechanical properties. However, its poor cross-plane thermal conductivity limits its use in some electronic applications. The electron distribution of graphene and the interaction with the base material can be greatly altered by introducing F, the most electronegative element, giving fluorinated graphene oxide (FG) with a high thermal conductivity. Herein, FG is prepared by grafting F atoms onto the surface of graphene oxide in a low-temperature solid-phase reaction with poly(vinylidene fluoride) as a fluorine source. This method can effectively avoid the use of dangerous substances such as HF and F2. The FG dispersion and aqueous poly(vinyl alcohol) (PVA) solution are sequentially vacuum-filtered to obtain the FG/PVA composite film. After natural drying and hot-pressing, the thermal conductivity of the N-FG/PVA film is enhanced by the hydrogen bond between F of FG and the hydroxyl group of PVA. The in-plane and cross-plane thermal conductivity of an N-FG/PVA film containing 10.4 wt % FG are 7.13 and 1.42 W m-1 k-1, respectively. The film has a tensile strength of 60 MPa and an elongation at a break of 28%, which is promising for the thermal management of flexible electronic devices.
Keywords: flexible films; fluorinated graphene; hydrogen bond; poly(vinyl alcohol); thermal management capability.