Wall Density-Controlled Thermal Conductive and Mechanical Properties of Three-Dimensional Vertically Aligned Boron Nitride Network-Based Polymeric Composites.

Polymeric composites with good thermal conductive and improved mechanical properties are in high demand in the thermal management materials. Construction of a three-dimensional (3D) structure has been proved to be an effective method to obtain polymeric composites with improved through-plane thermal conductivity (TC) for efficient thermal management of electronics. However, the TC enhancement of the obtained polymeric composites is limited, mainly due to poor control of the 3D thermal conductive network. Additionally, achieving high thermal conductive properties and enhanced mechanical properties simultaneously is of great challenge for polymeric composites. In this work, a 3D boron nitride framework (BNF) with a well-defined vertically aligned open structure and designed wall density fabricated by a unidirectional freezing technique was applied. The as-prepared BNF/polyethylene glycol (PBNF) composites exhibit enhanced through-plane TC, excellent thermal transfer capability (ΔTmax = 34 °C), and improved mechanical properties (Young's modulus enhancement up to 356%) simultaneously, making it attractive to thermal management applications. Strong correlation between the TC and mechanical properties of the PBNF composites and the wall density of the BNF scaffolds was found, providing opportunities to tune the TC and mechanical properties through the controlling of wall density. Furthermore, the models between TC and Young's modulus of PBNF composites were established by using the data-driven method "sure independence screening and sparsifying operator", which enables us to predict TC and Young's modulus of the polymeric composites for designing promising composite materials. The design principles and fabrication strategies proposed in this work could be important for developing advanced composite materials.