One-step alkyl-modification on boron nitride nanosheets for polypropylene nanocomposites with enhanced thermal conductivity and ultra-low dielectric loss

Polymer composites are widely used in microelectronics and wireless communication, wherein high thermal conductivity and low dielectric loss are highly pursued for efficient heat dissipation and signal transmission. However, improvement of thermal conductivity via combination of thermo-conductive additives usually accompanies with surge of dielectric loss, due to the serious interfacial polarization and phonon scattering, leading to a long-standing blank of thermo-conductive composites with minimized dielectric loss. Considering that polymer-additive interface and additive dispersion are believed to play key roles in two performances, herein, we report a low-loading (5.5 vol%) polypropylene (PP) nanocomposites with uniform-dispersed and interfacial engineered boron nitride nanosheets (BNNS) via one-step alkyl modification. Attributed to stronger interfacial noncovalent interactions between BNNS and macromolecular chain to suppress the interfacial polarization, and well-maintained hexagonal crystalline lattice of BNNS to promise phonon transmission, this artificial PP nanocomposites film behaves a much enhanced thermal conductivity of 2.74 W/m·K and remarkably low dielectric loss of only 0.002; these thermal and dielectric performances could outperform mostly ever reported thermo-conductive polymer-based dielectrics. Along with prominent electric breakdown strength, flexibility and stretchability, this study offers an easy avenue and provides some guidance for fabricating thermo-conductive dielectrics with low dielectric loss.