Manipulation of the ultimate pattern of polypyrrole film on self-assembled monolayer patterned substrate by negative or positive electrodeposition

Micro printed self-assembled monolayer may lead to different ultimate patterns of polypyrrole (PPy) by way of positive or negative deposition in guiding the electrodeposition of pyrrole. This article gives a detailed investigation of the effects of experimental conditions on the ultimate patterns of the PPy films on self-assembled monolayer (SAM)-patterned silicon and gold substrates. The effects of the substrate surface electric properties and the nature of the solvent and supporting electrolyte on the selective deposition and the PPy film morphology are also discussed. As the results, negative deposition occurs on the octadecyltrichlorosilane (OTS)-covered area of semiconductor Si surface in non-aqueous acetonitrile solution and results in positive patterns, while positive deposition occurs in aqueous solution and gives birth to negative patterns. This is attributed to the accessibility of the monomer solution to the substrate surface. The electrodeposition preferentially occurs on the exposed area of a gold substrate, though the deposition on the octadecanthiol (ODT)-covered area is unavoidable due to the hydrophobic-hydrophobic interaction. The lypophilic properties of the deposited PPy can be modified by selecting different salts as the supporting electrolytes and doping different anions during the electrodeposition. Subsequently, the morphology of the electro-deposited PPy layer can be tailored making use of the interaction between the PPy oligomer and the surfaces of different chemical functionalities.