Electrically conductive polymer nanocomposites have been applied extensively in many fields to develop the next generation devices. These nanocomposites are of great importance in achieving enhanced mechanical and/or optical properties such as transparency, flexibility, and adhesive strength. However, it is very difficult to achieve both high electrical conductivity and good physical properties because large amount of conductive nanofillers are required for sufficiently high electrical conductivity, which in turn deteriorates the desired physical properties of nanocomposites. A conductive polymer nanocomposite is composed in the form of conductive nanofillers dispersed in an insulating polymer matrix. Therefore, stable dispersion of nanofillers is crucial to obtain enhanced conductivity with a small amount of conductive nanofiller.
In this study, we prepared the electrically conductive epoxy/silver nanowire (AgNW) nanocomposites by the introduction of silica nanoparticles (SNPs), and investigated the effect of SNP addition on the electrical and mechanical properties of the nanocomposites. SNPs were synthesized by the sol-gel method, and AgNWs were synthesized by the polyol method. The epoxy/AgNW nanocomposites incorporated with SNPs showed better electrical conductivity compared to the epoxy/AgNW counterparts without silica, mainly because the van der Waals attraction between SNPs and AgNWs dominates over the depletion-induced interaction between AgNWs, thus improving the dispersion of AgNWs. In the nanocomposites of AgNW 3 vol%, electrical properties were not increased without SNPs but sharply increased with the addition of SNPs. It seems that the electrical network of AgNWs could be formed at SNP 3.9 vol%. With the addition of SNP 5.26 vol% and 7.89 vol%, the electrical percolation threshold of epoxy/AgNW nanocomposites was AgNW 1.49 vol% and 1.43 vol%, respectively. In the case of SNP 7.89 vol% the electrical conductivity of AgNW 4 vol% was as high as 100 S/m.