  We report polymer composite films containing fillers comprised of
quasi-one-dimensional (1D) van der Waals materials, specifically transition
metal trichalcogenides containing 1D structural motifs that enable their
exfoliation into bundles of atomic threads. These nanostructures are
characterized by extremely large aspect ratios of up to 10^6. The polymer
composites with low loadings of quasi-1D TaSe3 fillers (below 3 vol. %)
revealed excellent electromagnetic interference shielding in the X-band GHz and
EHF sub-THz frequency ranges, while remaining DC electrically insulating. The
unique electromagnetic shielding characteristics of these films are attributed
to effective coupling of the electromagnetic waves to the high-aspect-ratio
electrically-conductive TaSe3 atomic-thread bundles even when the filler
concentration is below the electrical percolation threshold. These novel films
are promising for high-frequency communication technologies, which require
electromagnetic shielding films that are flexible, lightweight, corrosion
resistant, electrically insulating and inexpensive.
