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1 ature anotechnology reference number: AO A Growth and alignment of polyaniline nanofibres with superhydrophobic, superhydrophilic and other properties an-rong Chiou 1,2,3, Chunmeng Lu 1, Jingjiao Guan 2, L. James Lee 1,2 and Arthur J. Epstein 2,3,4 * 1 Department of Chemical and Biomolecular Engineering, The Ohio State University, Columbus, O (USA), 2 The Center for Affordable anoengineering of Polymer Biomedical Devices, The Ohio State University, Columbus, O (USA), 3 Department of Physics, The Ohio State University, Columbus, O (USA) 4 Department of Chemistry, The Ohio State University, Columbus, O (USA) * epstein@mps.ohio-state.edu (a) (b) Figure S1 Scanning electron micrograph (SEM) of the thin film deposited on PET over-head transparency. a, Dilute polymerization; tilted view. b, Conventional polymerization 8,19 ; tilted view. Dilute polymerization condition: [aniline] = 0.01M, [aniline]/[aps] = 1.5, [ClO 4 ] = 1M, Temperature = 0~5 o C (ice bath), stirring of the reaction mixture and reaction time = 24 hours. 1 Conventional polymerization condition: [aniline] = 0.438M, [aniline]/[aps] = 4.35, [ClO 4 ] = 1M, Temperature = 0~5 o C (ice bath), stirring of the reaction mixture and reaction time = 1.5 hours. Page 1 of ature Publishing Group

2 Top view Tilted view PMMA micropillars Dilute polymerization Top view Tilted view Aligned nanofibre coating Figure S2 Scanning electron micrograph (SEM) of aligned polyaniline nanofibres grown on the surface of PMMA micropillars which were fabricated by hot embossing microfabrication. The procedures of micropattern formation are described as below. The microfeatures (pillar array) were prepared using standard photolithography. MDS (adhesive promoter) and 1813 photoresist were spun onto a silicon wafer sequentially. After soft bake and exposure, the substrate was developed using MF-319 developer. The PDMS daughter mold was obtained by having 10:1 (w/w) base/curing agent of poly(dimethyl siloxane) (PDMS) thoroughly mixed and degassed under vacuum for 30 minutes. It was then poured over the mother mold and cured on a hot plate at 70 C for hours. The PDMS daughter mold was used to produce PMMA micropillars through a micro compression molding process. Briefly, the PMMA pellets were put between a PDMS mold and a glass/metal top cover. The chip thickness is controlled by a metallic spacer. The setup was then put into a hot press (CARVER) and the temperature was set to 180ºC. After the pellets were melted, which usually took more than 15 minutes, the hot press was pressed down. After the press was cooled down, the chip was taken out and the PDMS was peeled off the PMMA chip. Page 2 of ature Publishing Group

3 1.2 1 Absorbance Wavelength (nm) Figure S3 UV/vis spectrum of the thin film of aligned polyaniline nanofibres grown on PET overhead transparency. As-synthesized thin film is in-situ doped by ClO 4 and then dedoped by 0.1M of 4 O (aq). The undoped film is redoped by 1M of Cl (aq) (solid line). Polymerization condition: [aniline] = 0.01M, [aniline]/[aps] = 1.5, [ClO 4 ] = 1M, Temperature = 0~5 o C (ice bath), stirring of the reaction mixture and reaction time = 24 hours. The absence of a strong signature of a localized polaron peak at ~800 nm and the presence of a broad slowly varying absorption (free carrier tail) for wavelengths longer then 750 nm supports substantial delocalization of mobile charge within the aligned nanofibres. Page 3 of ature Publishing Group

4 Figure S4 Scanning electron micrograph (SEM) of the thin film deposited on PET over-head transparency. Polymerization condition: [aniline] = 4 ~ 400mM (mm: millimolar), [aniline]/[aps] = 1.5, [ClO 4 ] = 1M, Temperature = 0~5 o C (ice bath), stirring of the reaction mixture and reaction time = 24 hours. The morphology of the aligned nanofibres is sensitive to the concentration of the reagents used for polymerization. When the initial concentration of aniline is used in the range of 8mM to 12mM and the reaction is performed at low temperature (e.g., 0~5 o C), all in-situ deposited thin films show a similar morphology to the dense array of aligned nanofibres. There is no apparent difference in the morphology of the aligned polyaniline nanofibres when the sizes of the reaction chambers or containers (reaction volume) are reduced or increased several fold, as long as the initial concentration of aniline is fixed in the above range. The morphology of aligned polyaniline nanofibres for the same polymerization conditions is reproducible. This indicates that the method we demonstrate here allows one to scale up the coating of the aligned nanofibres on various substrates. For example, we have successfully deposited the aligned nanofibres onto substrates of a wide variety of sizes and geometries, including PET microfibres (e.g., average diameters ~ 20 μm), microchannels (e.g., 60 μm ~ 500 μm in width) and micropillars (e.g., 1 μm ~ 20 μm in diameter), 8.5 x 11 PET transparencies, glass slides of various sizes, ITO coated glass slides of various sizes, etc. The same morphology is also observed on molecularly-modified substrates (e.g., 3-aminopropyltriethoxysilane (APTES)-modified glass or polyallylamine hydrogen chloride (PA)-modified PET). The free-standing thin films collected at the interface of air and reaction solution also show the same morphology as that found on the substrates. Reaction temperature, mixing conditions (stirring or no stirring) and choice of dopant acids (e.g., inorganic acids (ClO 4 or Cl, etc) and organic acids) only slightly affect the final morphology. owever, the uniformity of the coating is improved when the monomer and oxidant are distributed homogenously during polymerization at low temperature. (Scale bar = 500nm) Page 4 of ature Publishing Group

5 (b) (a) x Rx time = 3min a 2 S 2 O 5 (aq) SO 3- SO x (c) Rx time = 2days18h Figure S5 ucleophilic addition to aligned polyaniline nanofibres. The arrays of the aligned nanofibres coated on PET over-head transparency of various sizes were suspended in the aqueous solution of 0.1M of sodium metabisulfite, sodium bisulfite or sodium sulfite for the desired time at room temperature. The modified samples were purified or rinsed several times by copious quantities of deionized water. a, Aligned nanofibres of emeraldine base before undergoing nucleophilic addition reactions with sulfite ions. b, Undergoing nucleophilic addition reaction for 3 minutes. c, Undergoing nucleophilic addition reaction for 2 days and 18 hours. (Rx time: Reaction time) Page 5 of ature Publishing Group