Elucidating the Parameters Governing Thermal Transport In Polymer Nanocomposites
Polymers are attractive candidates for the packaging industry given their ease of processing, abundance, and versatility. The poor thermal transport properties of these materials, however, limit their application in the packaging of high energy density materials. To circumvent this shortcoming, much work has gone into embedding thermally conductive additives into polymer matrices to enhance the overall thermal conductivity (k)). Predicting composite thermal conductivity (k) has shown to be difficult given the thermal boundary resistance (TBR) present at the particle matrix interface and the limited understanding of parameters effecting TBR. While previous work has explored effects of bond strength at inorganic−organic interfaces, nothing has been established pertaining to the interface of organic constituents in polymer nanocomposites. Using surface initiated atom transfer radical polymerization (SIATRP), it is possible to synthesize nanoparticles grafted with well defined polymer ligands of known length, architecture, and identity (typically termed particle brushes). By isolating and comparing parameters such as graft architecture and graft-matrix interactions in particle brush/polymer blends, it is possible to begin understanding organic−organic interface effects on thermal transport in polymer nanocomposites. The work of this thesis focuses on the effects of introducing enthalpically favorable interactions at the organic−organic interface of particle brush/polymer blends and the effects of chain confinement in surface tethered polymer chains on thermal transport properties in polymeric systems. It is found that incorporating enthalpically favorable interactions at the organic−organic interface renders k values greatly exceeding those of theoretical predictions while inducing chain alignment in particle and polymer brush systems only show minimal enhancements, contradicting trends seen in bulk polymer systems and further highlighting the significance of interface effects on k in polymer nanocomposites.