Improved thermal conductivity and excellent electrical insulation properties of polysiloxane nanocomposite-incorporated functional boron nitride sheets <i>via in situ</i> polymerization

Abstract

Benefiting from its high thermal conductivity (<i>κ</i>) and superior insulation, the boron nitride nanosheet (BNNS) is widely investigated as a promising filler for thermal nanocomposites. However, poor dispersibility and weak interaction with polymer matrix hinder the further improvement of BNNS-based thermal composites. Here, inspired by side-chain liquid crystal polysiloxane (SCLCP) with good mesomorphic structures, highly thermoconductive nanocomposites prepared <i>via in situ</i> polymerization using SCLCP with 2D BNNS are reported. The surface of BNNS is silanized with γ-(methacryloxy)propyltrimethoxysilane (KH-570) to introduce double bonds (defined as f-BNNS), and it is directly linked with SCLCP chains during polymerization. Therefore, the alternating stacking of f-BNNS and microscopic ordered structure of SCLCP yielded a high <i>κ</i> of 2.463 W m^-1 K^-1 at only 30 wt% f-BNNS content, improving dramatically the <i>κ</i> of pure SCLCP by ∼9 times. Further, the volume electrical resistivity reached 2.11 × 10¹⁴ Ω cm, which is five orders of magnitude higher than the critical resistance for electrical insulation (10⁹ Ω cm). Also, the f-BNNS/SCLCP composites as thermal management materials decreased the temperature of the LED chip by 17.5 °C, exhibiting superior thermal management performance. Along with high <i>κ</i> and excellent electrical resistance, this type of nanocomposites displays great advantages in thermal properties for electronic packaging and thermal management of electronics.