Design of Electric Field-Induced High Thermal Conduction Routes in Polymer-Based Nanocomposites with Low Amount of Boron Nitride Nanosheets (≤20 vol%)

Abstract

Polymeric nanocomposites with high thermal conductivity with and without electrical insulating properties are great potential for thermal interface materials (TIMs) in semiconductor industry, in particular, in the field of high-power-density electronics and optoelectronics. Conventional materials require a large amount, over 70 vol%, of electrically conducting fillers such as carbon allotropes to attain thermal conductivities more than 1 W/mK. However, due to the incorporation of large quntities of expensive fillers and enevitible increase of viscosity are inefficient cost-effectiveness and processibility. Here, we introduce electric field-induced application techniques to control the assembly of inorganic micro- or nanofillers at a low level of filler loading less than 20 vol% and to achieve enhancement of thermal conductivity in polymer matrix. Boron nitride (BN) nanosheets have been incorporated into electrically insulating polysiloxane matrix to generate high thermally conductive routes inside the nanocomposites. The homogeneous suspension of filler particles and prepolymer mixture was cast woth 200~300 μm thickness and subjected to different electric fields. Analysis showed that BN nanosheets were fabricated in the hybrid films with oriented or linear assembles perpendicular to the film surface with high anisotropy. In particular, the thermal conductivity of composites with controlled assembly of BN nanosheets could be increased to 1.56 W/mK only using 15 vol% of BN fillers which was over 500% of composite with random distribution. Mechanisms for the field-induced fabrication and structural variation of the two dimensional filler assembly in the polymer matrix are elucidated in relation to enhancement of the thermal properties. This technique provides a facile, controllable approach that can be extended to the synthesis of other TIMs in based on polymer-based nanocomposites.