Longitudinal and Lateral Integration of Conducting Polymer Nanowire Arrays via Block-Copolymer-Templated Electropolymerization

Pyrrole (Py) and thiophene derivatives were electropolymerized on a microphase-separated block copolymer [PEO-b-PMA(Az)] coated ITO electrode in order to form the,corresponding conducting polymer nanostructures of perpendicularly oriented and hexagonally arranged cylinders as a template without the removal of one of the domains. Polypyrrole (PPy) nanowires grew through PEO cylindrical domains oriented perpendicular to the electrode to afford an array with an aspect ratio of up to 140 and a density of up to 4.4 x 10(12) wires/in.(2). Long, straight, pi-stacked crystalline structures assigned to PPy main chains were observed in high-resolution TEM images of the individual wires. Additional elaborately crafted electropolymerization was demonstrated on a nanometer scale: (i) stepwise electropolymerization of Py and 3,4-ethylenedioxythiophene (EDOT) afforded segmented PPy poly(3,4-ethylenedioxythiophene) (PEDOT) and PEDOT PPy wires with nahoheterojunctions and (ii) one-pot electropolymerization of a Mixture of Py and 2,2'-bithiophene (BiTh) polymerized selectively and nonselectively in the PEO cylindrical domains, giving lateral-composition-modulated structures, i.e., a PPy-poly(2,2'-bithiophene) (PBiTh) copolymer [P(Py-co-BiTh)] in the PEO cylindrical domains and PBiTh in the surrounding PMA(Az) domains. Both longitudinally segmented and laterally mosaic nanostructures of the conducting polymers can be fabricated just by utilizing the relative solubility of the monomers in the individual domains, herein called a chemical affinity template.