Rheological and electrical percolation behaviors of polyvinyl alcohol/silver nanowire suspensions using different aspect ratio silver nanowires

The rheological and electrical properties of polyvinyl alcohol (PVA)/silver nanowire (AgNW) suspensions and films are investigated with increasing AgNW concentrations, employing AgNWs with two different aspect ratios, namely 714 and 1000 (referred to as Ag714 and Ag1000, respectively). To estimate the effect of the aspect ratio on the rheological and electrical percolation behavior, the linear rheological properties of suspensions and the electrical properties of the resulting films are systematically assessed. The microstructure of the suspensions and the surface morphology of the films are visualized using optical microscope (OM) and field emission scanning electron microscope (FE-SEM), respectively. Observations from OM analyses reveal that suspensions containing higher aspect ratio AgNW (Ag1000) exhibit larger flocculated clusters, resulting from the entanglement of the nanowires. As results, PVA/Ag1000 suspensions show higher linear viscoelasticity (as indicated by G′ and G″) when compared to PVA/Ag714 suspensions. However, unlike linear viscoelasticity, the electrical conductivities of PVA/Ag1000 films are lower than those of PVA/Ag714 films. This observation is attributed to the alignment of AgNWs during coating process providing substantial deformation and rapid alignment. Furthermore, SEM images of the films confirm the importance of retaining the flocculated clusters to achieve the desired electrical properties.