Selective Deposition of Conducting Polymers on Hydroxyl-Terminated Surfaces with Printed Monolayers of Alkylsiloxanes as Templates

This paper describes the use of patterned self-assembled monolayers (SAMs) in area-selective deposition of conducting polymers (polypyrrole and polyaniline) on insulating, hydroxyl-terminated surfaces such as Si/SiO2 and glass. Patterned SAMs of octadecylsiloxane were generated on the hydroxyl-terminated surfaces using microcontact printing; they defined and directed the deposition of conducting polymers. The rate of deposition on the hydrophobic surface is higher than that on the hydrophilic surface: immersion of a substrate patterned with a methyl-terminated SAM in an appropriate aqueous polymerization bath produced a "positive" pattern of the conducting polymer on the surface. The conducting polymer deposited on the hydrophobic region of a surface completely covered by the polymer could be readily removed by transferring it to adhesive tape to form a "positive" pattern on the tape, leaving a "negative" pattern on the surface of the substrate. The conducting polymer deposited on the hydrophobic surface had a more extended conformation, and thus a higher conductivity (approximately 3 orders of magnitude in difference), than that formed on the hydrophilic surface. The smallest features of conducting polymers generated using these procedures were ∼2 μm in lateral dimension. The edge roughness of these patterns was ∼0.5 μm. These patterned microstructures of conducting polymers were conductive; they have been used as electrodes in display devices based on polymer dispersed liquid crystals.