Anisotropic thermally conductive flexible films based on nanofibrillated cellulose and aligned graphene nanosheets

Abstract

The anisotropic thermally conductive flexible films with nanofibrillated cellulose (NFC) and in situ reduced graphene oxide (RGO) nanosheets are prepared via a vacuum-assisted self-assembly technique. The hybrid films exhibit superior in-plane thermal conductivities, and a value of 6.168 W m⁻¹ K⁻¹ is achieved with 30 wt% GO loading. Noteworthily, the through-plane thermal conductivities are extremely low (≤0.072 W m⁻¹ K⁻¹). The high anisotropy of the thermal conductivity is systematically investigated and correlated to the alignment of RGO nanosheets. Moreover, hybrid films exhibit excellent flexibility as well as high tensile strength. The aligned RGO nanosheets significantly delayed the thermal degradation of the hybrid films. The strongly anisotropic thermally conductive properties of these films can be useful for their application in thermal management.