Formation of thin transparent conductive composite films from aqueous colloidal dispersions

This investigation examines the percolation and electrical resistivity behavior of films containing electrically conductive antimony-doped tin oxide particles in different polymer matrices. The polymers include gelatin, a soft polymer latex (glass transition temperature T-g < room temperature), and a hard polymer latex (T-g > room temperature). The films are formed through the evaporation of water from aqueous dispersions of conductive particles and film-forming polymers. The critical volume fraction of conductive particles for conductive network formation was found to be significantly lower when the film former was a polymer latex. This was attributed to differences in the interactions of particles in the colloidal state prior to the point where particles start to touch. In the critical transition region or slightly above the critical transition region, the hard latex provides an order of magnitude improved surface resistivity compared to that of the soft latex. This result was discussed in terms of the polymer particle deformation and flow during the film formation process.