Polydioxythiophene nanodots, nonowires, nano-networks, and tubular structures: the effect of functional groups and temperature in template-free electropolymerization.

Various nanostructures, including nanofibers, nanodots, nanonetwork, and nano- to microsize tubes of functionalized poly(3,4-ethylenedioxythiophene) (EDOT) and poly(3,4-propylenedioxythiophene) (ProDOT) are created by using a template-free electropolymerization method on indium-tin-oxide substrates. By investigating conducting polymer nanostructures containing various functional groups prepared at different polymerization temperature, we conclude a synergistic effect of functional groups and temperature on the formation of polymer nanostructures when a template-free electropolymerization method is applied. For unfunctionalized EDOT and ProDOT, or EDOT containing alkyl functional groups, nanofibers and nanoporous structures are usually found. Interesting, when polar functional groups are attached, conducting polymers tend to form nanodots at room temperature while grow tubular structures at low temperature. The relationship between surface properties and their nanostructures is evaluated by contact angle measurements. The capacity and electrochemical impedance spectroscopy measurements were conducted to understand the electrical properties of using these materials as electrodes. The results provide the relationship between the functional groups, nanostructures, and electrical properties. We also discuss the potential restriction of using this method to create nanostructures. The copolymerization of different functionalized EDOTs may cause irregular and unexpected nanostructures, which indicates the complex interaction between different functionalized monomers during the electropolymerization.