Higher power density and power consumption in electronic devices require heat dissipating components with high thermal conductivity to prevent overheating and improve performance and reliability. Polymers offer the advantages of low cost and weight over metallic components, but their intrinsic thermal conductivity is low. Previous studies have shown that the thermal conductivity in polymers can be enhanced by aligning the polymer chains or by adding high thermal conductivity fillers to create percolation paths inside the polymeric matrix. Traditionally, aligning the conductive fillers has been utilized to achieve polymer composites with enhanced, but still moderate, in-plane thermal conductivity but limited cross-plane thermal conductivity. Yet, cross-plane thermal conductivity plays a vital role in dissipating heat from active devices and transmitting it to the surrounding environment. In this study, I combine conductive fibers and fillers to enhance thermal conductivity of polymers without significantly inducing thermal anisotropy, while preserving the mechanical performance of the matrix.

 

I employ three approaches to enhance the thermal conductivity (𝑘) of thermoset polymeric matrices. In the first approach, I fabricate thermally conductive polymer composites by creating an emulsion consisting of eutectic gallium indium alloy (EGaIn) liquid metal in the uncured polydimethylsiloxane (PDMS) matrix. In the second approach, I create another polymer composite by infiltrating Ultra High Molecular Weight Polyethylene (UHMW-PE) chopped fiber mats with an uncured epoxy resin. In both cases, the polymers are cured at 70°C. Finally, the third approach combines the two previous methods, where I prepare an emulsion of the liquid metal in the uncured epoxy matrix to subsequently infiltrate the UHMWPE fiber mat.

 

I evaluate the thermal performance of the composites using infrared thermal microscopy with two different experimental setups, enabling us to independently determine values for in-plane and cross-plane thermal conductivity. The results demonstrate that incorporating thermally conductive fillers enhances the overall conductivity of the polymer composite. Moreover, I demonstrate that the network structure achieved by the fiber mat, in combination with the presence of liquid metal, promotes a more uniform increase in the thermal conductivity of the composite in all directions. Additionally, I assess the impact of filler incorporation and filler concentration on matrix performance through tension, indentation, and bending tests for mechanical characterization of my materials. These results demonstrate the potential of strategic polymer design to achieve polymers with isotropically high thermal conductivity. These results demonstrate the potential of strategic polymer design to achieve polymers with isotropically high thermal conductivity, offering a solution to the challenges posed by higher power density and consumption in electronics and providing improved heat dissipation capabilities for more reliable devices.