Electrostatic self‐assembly of barnacle‐like modified <scp>BN</scp>@<scp>ND</scp> hetero‐structured fillers to synergistic enhanced thermal conductivity of <scp>PI</scp> composite films

Abstract High‐integration microelectronic equipment cannot dissipate heat for long periods of time, which enormously damages the efficiency and service life of electronic devices. Developing polymer‐based composite film exhibiting admirable thermal conductivity (TC), mechanical, dielectric and insulation performances has been pursued by researchers. Polyimide (PI) materials are generally used in progressive electronic systems. In this research, we constructed unique thermally conductive fillers to improve the TC of PI composites. Specifically, boron nitride nanosheets (BNNS) and nanodiamond (ND) were modified to impart them different charging properties. The barnacle‐like hetero‐structured fillers (MBN@FND) were assembled by electrostatic self‐assembly, and then introduced into PI to prepare PI composites. MBN@FND‐2 (MBN/FND, 1/1, wt/wt) fillers exhibited optimal morphology. The results showed that MBN@FND formed tightly stacked structure in composites, availing the densification of the thermal network and improving the heat transfer efficiency. Under 25 wt% MBN@FND loading, the in‐plane TC of MBN@FND/PI composite was 9.73 W/mK, and the through‐plane TC was 0.72 W/mK. The MBN@FND/PI composite remained at a low level in terms of dielectric properties. Moreover, MBN@FND/PI composites had flexibility, good tensile strength (47.9 MPa), and volume resistivity of 1.05 × 10 13 Ω cm. This work provides a versatile approach for the preparation of hybrid materials. Highlights Hetero‐structured fillers were prepared by electrostatic self‐assembly. The in‐plane TC and through‐plane TC of PI composite was improved. The composites had insulation, flexibility, and low dielectric properties.