High thermal conductivity and low dielectric polyimide nanocomposites using diamine-assisted mechanochemical exfoliation boron nitride and in-situ polymerization under pressure

Advanced integrated circuit materials demand polymer composites with exceptional thermal conductivity and low dielectric constant to minimize power consumption and improve signal transmission. However, conventional methods of improving the thermal conductivity of composites by incorporating thermal conductive fillers result in an increase in dielectric constant, producing a huge challenge in simultaneously achieving enhanced thermal conductivity and low dielectric constant. Herein, a brick-and-mortar structure has been successfully constructed through in-situ polymerization of the diamine-assisted mechanochemical exfoliated (DAME) boron nitride (BN) with trifluoromethyl-containing PI and microporous polyhedral oligomeric silsesquioxane (POSS) under pressure. The DAME functionalized BNNS (f-BN) exhibit high aspect ratios, few lattice defects, high yields and excellent dispersion in the POSS/PI matrix. Notably, the obtained 40 wt% f-BN/POSS/PI nanocomposite exhibits a high in-plane thermal conductivity of 17.76 W m−1 K−1 with a 488 % enhancement compared to 40 wt% hBN/POSS/PI, and simultaneously maintains low dielectric constant of 2.76 and low dielectric loss of 0.0042 at 1 MHz close to the pure POSS/PI matrix. Density functional theory is utilized to reveal the possible chemical reactions between f-BN and diamine, and the impacts of interfacial functionalization on the thermal conductivity and dielectric properties of nanocomposites are illustrated by molecular dynamics simulations. Furthermore, the DAME method demonstrates good universality among polyimide matrices, and shows excellent practical implementation as a thermal interface material and flexible printed circuit board. This material provides a promising solution for integrated circuits by successfully addressing the challenge of combining low dielectric constant and high thermal conductivity in microelectronic systems.