Conductive particle networks are key to achieve sufficient electrical conductivities in soft and flexible hybrid materials and composites. Conductive particles in an insulating polymer matrix result in macroscopic conductivity above a certain volume fraction, that depend on particle shape and the formation of networks. We study the network topology as a function of particle geometry, particle interactions, and the assembly process during material synthesis. We use 2D networks of the filler particles because they are accessible to detailed analyses.
In this work, we prepared silver particle monolayers using Langmuir-Blodgett-like methods and studied the resulting electrically conductive networks. The particles were chosen to represent typical conductive fillers. The sheet resistances were measured using the two-wire technique. In addition, the microscopic conductivity at the single-particle level was probed by resistive contrast imaging (RCI) of particles in the monolayer in situ using scanning electron microscopy. The findings were correlated with the properties of networks formed by the same filler particles in a silicone elastomer (polydimethylsiloxane, PDMS) matrix at different volume fractions.
We use the RCI results to discuss different metrics of 2D network metrics and draw first conclusions on the properties of 3D conductive particle networks.