A long-range ordered boron nitride/polyimide thermal interface material was designed based on the lamellar structure of crepe cake

• Long-range lamellar network is designed through a freezing process guided by double temperature gradient . • Long-range ordered structure is formed by regulating the thermal motion of polymer chain segments. • The long-range ordered structure of the composite provides a long-range conduction path for phonons. In recent years, boron nitride nanosheets (BNNS) have been widely used in the development of polymer-based thermal interface materials (TIM) due to their excellent thermal conductivity and electrical insulation. However, the thermal performance of these TIMs is still unsatisfactory, mainly because BNNS do not connect effectively in the polymer matrix. The lamellar structure of a crepe cake in life provides inspiration for the design of this study. In this study, TIM with long-range ordered structure was prepared by using the freezing process guided by double temperature gradient. The long-range ordered structure forces BNNS to be tightly connected and highly oriented between polymer layers, thus providing long-range conduction paths for phonons. The composite prepared by this strategy exhibits excellent in-plane thermal conductivity (10.4 W/(m·K)), volume resistivity, tensile strength and thermal stability at only 20 vol% BNNS loading, which makes it has a broad application prospect in the field of electronic device packaging. In addition, the strategy provided by the study can not only be applied to the development of thermal conductivity composites, but also can be extended to different material combinations of various functional composites.