Aligned conjugated polymers standing upright.

Conjugated polymers have enormous potential as novel electronic materials that combine the electrical properties of semiconductors with the good mechanical strength and processing advantages of plastics. [ 1 , 2 ] Perhaps nowhere is this more evident than in the synthesis of conjugated heterocyclic polymers based on thiophene units or monomers. [ 3 ] Owing to their facile preparation, relatively high conductivity, and good long-term stability under ambient conditions, these polymers have been the focus of intense study for use in devices such as plastic photovoltaics, light-emitting diodes, transistors, and fl exible displays. [ 4–6 ] The ability to change color, due to twisting of the polymer backbone in response to changes in solvent, temperature, applied potential, and binding to other molecules, also makes the polythiophenes attractive as optical sensors. [ 7 ] Despite the phenomenal growth in diverse synthetic methodologies that allow the fabrication of the polythiophenes with desired chain length and structure, however, the deposition and patterning of these molecules on a substrate has remained challenging. Conventional techniques for depositing fi lms of conjugated polymers include solution casting, dip coating, and spin coating of the polymer from solutions. However, for many conductive polymers, these approaches are often limited by the insolubility of the polymers, which form aggregates without extended molecular ordering upon deposition. Another common route to deposit conjugated polymers is through an electrochemical polymerization process on an electrode substrate that involves monomer oxidation, dimerization, and the growth of oligomers and polymers of the oxidized monomer. [ 8 ] Because of localized deposition of polymers at the electrode surface, this approach can be used to prepare patterned arrays of conjugated polymers on prepatterned electrodes. The standard procedures to create large-area conjugatedpolymer-array patterns generally involve sequential polymer deposition, photolithography, and a subsequent etching step to remove dissolved polymers by appropriate solvents. However, the ultraviolet light, typically used in the process of photolithographic patterning, may cause degradation of the conjugated polymers. In addition, many types of etching solvents can also dissolve and swell the conjugated polymer