Understanding dynamic percolation mechanisms in carbonaceous polymer nanocomposites through impedance spectroscopy: Experiments and modeling

Dynamic percolation refers to the impressive increase in conductivity in polymers filled with a constant filler content as a function of annealing time. We present a detailed study of the driving forces for this phenomenon. The organization of carbon nanotubes in a polymer melt is probed with a.c. conductivity. In contrast with the static percolation studied as a function of the filler content, two peaks are observed in the relative permittivity. We show that this new feature results from two distinct filler auto assembly mechanisms. The first one is ascribed to the relaxation of macromolecules and could be eliminated using the proper thermal treatment. The second mechanism is observed later in time. It is likely to correspond to a diffusion process of the carbonaceous filler similar to a phase separation. A phenomenological model is finally proposed to describe the changes in dispersion and distribution states with annealing time.