High-performance polyamide-imide films: Effect of functionalization degree of BN nanosheets

Abstract Chemical functionalization of boron nitride (BN) is necessary to improve the dispersion of the BN as well as interface compatibility within polymer matrix to enhance the properties of their composites. However, the degree of BN functionalization needs to be considered comprehensively to fully highlight the advantages. In the present work, a polyamide-imide (PAI) film with a parallel arrangement structure and designed functionalization of BN nanosheets by self-assembly technique is constructed. The design of optimum functionalization and defect control of the functionalized BN nanosheets (f-BNNSs) provides this flexible PAI/f-BNNSs composite film exhibits highly in-plane thermal conductivity, superior electrically insulating and improved mechanical properties. The thermal conductivity of the PAI/f-BNNSs film had an impressive improvement of 167%, from 5.06 W m−1 K−1 of PAI/BN film to 13.5 W m−1 K−1 of PAI/f-BNNSs film (PP1W3) at a low filler content of only 9 wt%. More importantly, systematic research was carried out in terms of the degree of functionalization, the quantities of defect of f-BNNSs and the performance of the composite films, which further revealed the mechanism of the thermal conductivity improvement of PAI/f-BNNSs composite films. This research provides significant guidance for the design of composite materials with excellent thermal conductivity based on the functionalization of low dimensional fillers, ensuring its application in the thermal management of high-power density electronic devices.