Interfacial region effect on thermal conductivity of silicon nanocrystal and polystyrene nanocomposites

Thermal transport has been widely studied in nanosize materials owing to their unique properties, including size-dependent thermal transport properties. Bulk-size nanostructures are often used for thermal property investigation as well as device applications. The nanocomposite structure of silicon nanocrystals (SiNCs) and polystyrene (PS) has been reported to have a significant thermal transport suppression attributed to the thermal resistance at material interfaces. Although the theoretical effective medium approximation (EMA) model for nanocomposites considers the thermal boundary resistance, a constant deviation is observed between the model and measurement results. In this study, the thermal transport of a polymer, which is known to be morphology dependent, is investigated in a region near the interfacial boundary. Nanocomposites were fabricated from SiNCs with significantly different diameters (6 and 60 nm), and their thermal conductivity was measured to analyze the effect of particle size on the effective thermal conductivity and its deviation. The results showed that the interfacial region of the PS matrix significantly affects the thermal transport, and the EMA model can be enhanced by modifying the thermal conductivity of the matrix owing to the confinement effect at the interfacial region; and the model and measurement results are in good agreement. This study shows that the interaction at material interfaces and its effect on the interfacial region play an important role in determining the thermal transport, opening up the possibility of controlling the thermal transport properties for wide applications of polymer-based nanocomposite devices.