Optically transparent and thermally conductive composite films of α-alumina and highly refractive polyimide

Optically transparent and thermally conductive polymer composites are required for next-generation opto-electronic devices. The present work aimed at creating polymer composite films with enough optical transparency and superior normal-to-plane thermal conductivity. We successfully prepared composite films with transmittances more than 80% (at a wavelength of 600 nm) and thermal conductivity more than 0.7 Wm(-1) K-1. For the polymeric matrix, we employed a highly refractive polyimide. alpha-alumina particles distributed in the polyimide matrix enhanced the normal-to-plane thermal conductivity of the composite films significantly. Similar refractive indices of the matrix polyimide and alpha-alumina particles suppressed light scattering in the polymer composites. The clever choice of the constituent materials conquered a trade-off between optical transparency and thermal conductivity in polymer composites.