Understanding the Source of Dielectric Loss in Titania/Polypropylene Nanocomposites up to 220 GHz

Nanocomposites are a promising new dielectric material for on-chip and chip-to-chip waveguides that operate at millimeter (mm)-wave frequencies because of their higher relative permittivity compared to neat polymers and their compatibility with printed circuit board processing. For dielectric waveguides, extremely low loss is critical; thus, understanding the origins of loss is an important step for these applications. In this paper, we investigate the sources of loss in TiO₂/polypropylene (PP) nanocomposites, in which polypropylene-graft-maleic anhydride (PP-g-MA) is added as a compatibilizer. Compared to nanocomposites made without PP-g-MA, we find that PP-g-MA improves the distribution of nanoparticles in the PP matrix and significantly lowers loss. We also examine the contribution to dielectric loss from PP-g-MA by measuring samples that contain no TiO2 nanoparticles, and find that while increasing the amount of PP-g-MA in PP results in a higher loss, it is small compared to the loss that comes from the addition of TiO₂ nanoparticles.