Transparent, conductive coatings from latex-based dispersions

Flexible, transparent and conductive coatings were prepared using polymeric latex as the matrix starting material, and transparent and conductive nanoparticles as the conductive filler. A stable aqueous dispersion of latex and conductive nanoparticles was prepared and deposited onto polymer substrates. Upon drying above the glass transition temperature of polymer, latex particles consolidated, compacted, deformed, and eventually coalesced, forcing the conductive nanoparticles into the boundary regions between latex and thereby resulting in a segregated microstructure. This segregated microstructure enables electrical conduction at relatively low filler concentration and optical transparency as well. The conductivity of the composite coatings is described by percolation theory.; The colloidal stability of the starting aqueous dispersions affects the coating microstructures and properties. A stable dispersion with the separated colloidal state dominated by electrostatic repulsion is desired for a good combination of conductivity and transparency.; The electrical properties of the composite coatings are affected by the physical morphology of latices and conductive fillers, the intrinsic resistivity of conductive fillers, and the interaction between matrix and filler. The transparency is affected by the distribution of conductive fillers in matrix and the refractive index difference between matrix and filler. As latex particle size increases, the conductivity percolation occurs at lower filler contents. As the intrinsic resistivity of filler decreases, the conductivity of the resulting composite coatings past the percolation threshold increases. So far, poly(3,4-ethylenedioxythiothene)/poly(4-styrenesufonate) PEDOT/PSS gel particles appear to be the best conductive filler due to their special morphology (water-swelled polymeric gel particles), high intrinsic conductivity (after polar solvent modification), and nearly matching refractive index with matrix polymer.; The mechanical properties of the ATO/latex coatings were investigated using depth-sensing nanoindentation techniques. Three types of methods, including a prolonged load holding time, analysis of the pull-off portion of the unloading curve, and dynamic indentation, were used to reduce the effect of creep deformation. The effects of ATO loading on mechanical properties were discussed. Dynamic indentation appears to be the best technique to generate reliable data in terms of the reduction degree of the effect of creep deformation.