Polymer nanocomposite films with thicknesses (≤ 30 μm) corresponding to the lateral dimension of graphite nanosheets as straightforward thermal conducting pathways

Herein, Polysiloxane-based nanocomposite films with controlled assembly of modified graphite nanosheets (GNs) are fabricated, and their thermal and optical properties are evaluated as potential thermal interface materials (TIMs). The micro-dimensional thickness of the composite films is chosen to be the same as the average lateral dimension of GNs in order to create straightforward thermal conducting pathways with oriented GNs and to minimize heat loss through the polymer matrix. Paramagnetic iron oxide nanoparticles are deposited on the surface of GNs, which were obtained by the exfoliation of graphite flakes via chemical vapor deposition, and their anisotropic orientation inside a pre-polymer of polysiloxane is controlled by application of a magnetic field (0.45 T). The analysis revealed that the modified GNs were perpendicularly-oriented and anchored the film surfaces of the composite with high anisotropy under the application of a magnetic flux. The controlled assembly of GNs (5 wt%) enhanced the thermal diffusivity of the composites by 330% and 200% compared to a pristine polymer and a corresponding composite with a random distribution of GNs, respectively. The enhancements of the optical and thermal properties were elucidated in terms of variations in the magnetic susceptibility of GNs as well as the increased thermal conduction.