Modified graphene/polyimide composite films with strongly enhanced thermal conductivity.

With the development of portable electronic devices, highly efficient thermal management has become an important design consideration which requires good flexibility and excellent thermal conductivity. In this work, an integrated "modified-welding" method is used to deliver a flexible film with superior thermal conductivity. Firstly, graphene oxide (GO) is modified by 4,4'-diaminodiphenyl ether (ODA) through covalent bonding, aiming at providing reactive sites by polyimide (PI) on GO sheets for further in situ "modified-welding". The intercalated PI in mGO film layers serves as the solder to weld adjacent graphene sheets into large ones with less grain boundaries, leading to a superior in-plane thermal conductivity of the graphitized graphene/polyimide composite film (g-mGO/PI) which reaches 1352 ± 5 W m-1 K-1, 92.3% higher than that of the pristine graphitized graphene film (g-GO). Additionally, the g-mGO/PI film survives a 2000-cycle anti-bending test, which demonstrates excellent flexibility. Last but not least, the "modified-welding" strategy also provides an innovative way to develop graphene-based films for thermal management.