Enhanced thermal conductivity of epoxy composites reinforced with oriented polydopamine-graphene foam complexed by metal ions

• High-quality graphene prepared by electrochemical exfoliation. • Modification of graphene with dopamine. • Construction of PGF using metal ion-assisted gelation pathway. • The unidirectional freezing enables the foam to have a vertically aligned structure. • PGF/EP composite exhibits high thermal conductivity and excellent electrical insulation. Although graphene has aroused considerable interest in the thermal conductive enhancement of polymer composites for its superb intrinsic thermal conductivity, the enhancement efficiency is still limited by its production-induced defects, misalignment and intense phonon interface scattering. Herein, the three-dimensional (3D) polydopamine-graphene foam (PGF) with high orientation and good interfacial bonding has been prepared by electro-exfoliation, surface modification and unidirectional-freezing. This unique structure imparts excellent thermal conductivity, electrical insulation and good mechanical property to the PGF/epoxy (PGF/EP) composite. The highly arranged and compact stacked PDA-graphene sheets bound by metal ions provide heat conduction paths for effective phonon transport within the matrix. The manufactured PGF/EP shows enhanced through-plane thermal conductivity of 3.48 W/m·K with 3.02 vol% of PGF, excellent surface & volume electrical resistivity (2.7 × 10 11 Ω & 1.65 × 10 11 Ω·cm) and high mechanical strength (82.74 MPa), as well as the outstanding heat dissipation performance. Therefore, the PGF/EP composites prepared in the present study have a broad application prospect in advanced electronic packaging materials.