Electrical, rheological, and mechanical properties of polystyrene/copper nanowire nanocomposites

The electrical, rheological, and mechanical properties of polystyrene/copper nanowire (PS/CuNW) composites at different CuNW compositions were studied. The copper nanowires were synthesized in our lab using a template-directed method with two different electrode sizes: 90 cm(2) (small scale) and 440 cm(2) (large scale). The nanocomposites were prepared using solution processing. The electrical percolation threshold of the nanocomposites occurs at a CuNW concentration between 0.50 and 1.00 vol % if the nanowires were produced on the small scale, and between 1.00 and 2.00 vol % if the nanowires were synthesized on the large scale. The dynamic rheological data at 200 degrees C indicate that the microstructure transition starts at 0.5% with the small-scale nanowires and at 1.1% with the large-scale nanowires, where a combined network of the polymer-nanowires, polymer-polymer, and nanowire-nanowire connections restrains the relaxation of the polymer chain. The morphological characterization by SEM and TEM reveals that the copper nanowires are dispersed in the polymer matrix both as agglomerates and as single nanowires. Tensile tests show that the Young's modulus increases, whereas the tensile strength and the elongation at break decrease, when the concentration of the nanowires increases.