Imidization-induced carbon nitride nanosheets orientation towards highly thermally conductive polyimide film with superior flexibility and electrical insulation

Owing to the unique layered structure, abundant functional groups and appropriate band gap, carbon nitride nanosheets (CNNS) has captured extensively attention in photocatalytic pollutants degradation and hydrogen evolution, while few study has been focused on improving the thermal conductivity. Considering its graphene-like network that is confined to 2D atomic thickness, CNNS would also show desirable thermal conductivity due to the highly aligned atoms decreasing phonon scattering. Here, CNNS is first used to improve the thermal conductivity of polyimide (PI) film. Based on the orientation of PI molecules during imidization and strong interaction with PI, CNNS realize in-plane self-orientation during solvent evaporation to form continuous thermal pathway in PI film. The thermal conductivity of PI/CNNS nanocomposite films reach 2.04 Wm(-1) K-1 with relatively low CNNS loading (20 wt%) which is about eleven times of the corresponding pure PI (0.18 Wm(-1 )K(-1)). Furthermore, the potential application of the PI/CNNS nanocomposite films for effective heat dissipation is explored by experiments and simulation. Meanwhile, the PI/CNNS nanocomposite films keep superior electrical insulation property and thermal stability. This work expands the application of CNNS and provides a facile, efficient approach to the design of high thermal conductive materials.