Drying-induced reduction in electrical resistivity of carbon black-polyamideimide nanocomposite films

We provide evidence that the electrical resistivity of carbon black (CB)/polyamideimide (PAI) composites are tunable by drying below the glass transition temperature of the polymer matrix. Solution casting experiments of N-methyl-2-pyrrolidone (NMP)/CB/PAI systems reveal that with increasing drying temperature, the measured volume resistivity reduces by four orders of magnitude in an intermediate range of particle volume fractions, which is between 12% and 15%. However, no temperature-dependence was observed for particle-free polymeric films and nanocomposites with high particle volume fractions, which is above 23%. The measured values obey a single master curve, independent of the primary size and surface pH of the nanoparticles. This suggests that the desorption of PAI molecules from the nanoparticle surface enhances the evolution of conductive pathway formation in the course of drying.