Polyelectrolyte-Coated Nanosphere Lithographic Patterning of Surfaces: Fabrication and Characterization of Electropolymerized Thin Polyaniline Honeycomb Films

Well-ordered 2-D polyaniline (PAni) honeycomb films were produced by electropolymerization of aniline within the interstitial voids in assemblies of polystyrene (PS) nanospheres precoated with poly(diallyldimethylammonium chloride) and poly(sodium 4-styrenesulfonate) (PDADMAC/PSS) thin shells, followed by the extraction of the PS cores with toluene. Depositing polyelectrolyte (PE) layers onto the PS particles was found to greatly improve the uniformity of the PAni attachment onto the PS particle surface. Through a systematic variation of the PE layer number and the electropolymerization parameters, PAni honeycomb films with desirable pore sizes, pore wall widths, and film thicknesses can be fabricated. Atomic force microscopy (AFM) and scanning electron microscopy were used to study the surface features of the resulting PAni honeycomb films, whereas electrochemical quartz crystal microbalance (EQCM) and reflectance FTIR measurements were carried out to verify the redox states of the PAni films and the composite nature of the pore walls. Assemblies constituting PS particles coated with four alternating PDADMAC and PSS layers yielded densely deposited PAni honeycomb films with evenly distributed pores. The PE shells within the pores of the honeycomb structure were found not to affect the overall properties of the PAni honeycomb films (e.g., conductivity, redox properties, and ion mobility within the films). Interestingly, the presence of PE/PAni composites at the pore walls appears to enhance the rigidity of the PAni film, as the extent of pore shrinkage was observed to be smaller with films produced with the template of PS particles precoated with a four or six PE layers. PE-coated nanosphere lithography followed by electropolymerization provides a unique method for constructing honeycomb films with patterns that are tunable and pores that are modifiable.