Creation of novel multiphase polymer materials, namely multi-component polymer blends and polymer nanocomposites (polymers with nanofillers) is field requiring creativity in polymer and inorganic chemistry, materials science, process engineering and physics. Polymer nanocomposites have unique multifunctional properties resulting from the size and shape of the fillers and display superior electrical, thermal and mechanical properties to conventional polymer composites due to the nanoscale size of the filler. By controlling the nanostructure of the fillers and the microstructure of the polymer composite, we can tailor specific properties. Multiwall carbon nanotubes (MWCNT), Silver and MnO2 nanowires, and MXene were melt-mixed with polymers via solution mixing and in miniature mixers, and electrical and mechanical properties were tested. Our group spans the entire materials development spectrum: (i) synthesis of nanofiller and copolymers, (ii) blending polymers with nanofiller to obtain desired morphology, (iii) development of miniature mixers for small scale (1g) and (iv) characterizing final properties. The electrical, mechanical and rheological properties of these materials were studied and evaluated for industrial applications such as personal electronics enclosures, shielding for aerospace, batteries and anti-static packaging. The morphology of the polymer nanocomposites was characterized by electron microscopy (TEM and SEM) and revealed unique segregated network structures that helped to significantly lower the electrical percolation threshold and increase electromagnetic shielding properties for applications such as cell phone and laptop enclosures. We attempt to understand the mechanisms of morphology development and resulting structure-property relationships.