title: Highly Anisotropic Thermal Conductivity of Layer-by-Layer Assembled Nanofibrillated Cellulose/Graphene Nanosheets Hybrid Films for Thermal Management.
abstract: An anisotropic thermally conductive film with tailorable microstructures and macroproperties is fabricated using a layer-by-layer (LbL) assembly of graphene oxide (GO) and nanofibrillated cellulose (NFC) on a flexible NFC substrate driven by hydrogen bonding interactions, followed by chemical reduction process. The resulting NFC/reduced graphene oxide (RGO) hybrid film reveals an orderly hierarchical structure in which the RGO nanosheets exhibit a high degree of orientation along the in-plane direction. The assembly cycles dramatically increase the in-plane thermal conductivity (λX) of the hybrid film to 12.6 W·m-1·K-1, while the cross-plane thermal conductivity (λZ) shows a lower value of 0.042 W·m-1·K-1in the hybrid film with 40 assembly cycles. The thermal conductivity anisotropy reaches up to λX/λZ= 279, which is substantially larger than that of similar polymeric nanocomposites, indicating that the LbL assembly on a flexible NFC substrate is an efficient technique for the preparation of polymeric nanocomposites with improved heat conducting property. Moreover, the layered hybrid film composed of 1D NFC and 2D RGO exhibits synergetic mechnical properties with outstanding flexibility and a high tensile strength (107 MPa). The combination of anisotropic thermal conductivity and superior mechanical performance may facilitate the applications in thermal management.
authors.affiliation: Research Centre of Nanoscience and Nanotechnology, Shanghai University , 99 Shangda Road, Shanghai 200444, People's Republic of China.
authors.forename: Na
authors.identifier: http://orcid.org/0000-0002-3343-3000
authors.initials: N
authors.lastname: Song
authors.affiliation: Research Centre of Nanoscience and Nanotechnology, Shanghai University , 99 Shangda Road, Shanghai 200444, People's Republic of China.
authors.forename: Dejin
authors.initials: D
authors.lastname: Jiao
authors.affiliation: Research Centre of Nanoscience and Nanotechnology, Shanghai University , 99 Shangda Road, Shanghai 200444, People's Republic of China.
authors.forename: Siqi
authors.initials: S
authors.lastname: Cui
authors.affiliation: Research Centre of Nanoscience and Nanotechnology, Shanghai University , 99 Shangda Road, Shanghai 200444, People's Republic of China.
authors.forename: Xingshuang
authors.initials: X
authors.lastname: Hou
authors.affiliation: Research Centre of Nanoscience and Nanotechnology, Shanghai University , 99 Shangda Road, Shanghai 200444, People's Republic of China.
authors.forename: Peng
authors.initials: P
authors.lastname: Ding
authors.affiliation: Research Centre of Nanoscience and Nanotechnology, Shanghai University , 99 Shangda Road, Shanghai 200444, People's Republic of China.
authors.forename: Liyi
authors.initials: L
authors.lastname: Shi
keywords: anisotropic properties; graphene nanosheets; layer-by-layer assembly; layered structure; nanofibrillated cellulose; thermal conductivity