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Template-Synthesis of Conjugated Poly(3-Hexylselenophene) (P3HS) Nanofibers Using Femtosecond Laser Machined Fused Silica Templates L. Costa,1,2 M. Al-Hashimi,3 M. Heeney,4 A. Terekhov,2 D. Rajput1,2, W. Hofmeister,1,2 A. Verma5 1

Department of Materials Science and Engineering, University of Tennessee - Knoxville, Tullahoma, Tennessee 37388, USA 2 Center for Laser Applications, University of Tennessee Space Institute, Tullahoma, Tennessee 37388, USA 3 Department of Chemistry, Texas A&M University at Qatar, P.O. Box 23874, Doha, Qatar 4 Department of Chemistry and Centre for Plastic Electronics, Imperial College London, London SW7 2AZ, UK 5 Department of Electrical Engineering & Computer Science, Texas A&M University - Kingsville, Kingsville, TX 78363, USA

Abstract: We report on the preparation of conjugated polymer nanofibers via templatesynthesis. A femtosecond laser machined fused silica template, with a micro-patterned array of high-aspect ratio surface nanopores, was first spin-coated with a polyvinyl alcohol (PVA) solution to form a water-soluble release layer. The PVA-lined template was then coated with a conjugated poly(3-hexylselenophene) (P3HS) – solvent solution. The solvent was allowed to dissipate, and the resulting {template / PVA liner / conjugated P3HS film} stack was then submerged in water to dissolve the PVA and release the conjugated polymer film from the template. The resulting conjugated polymer film exhibits an array of micro-patterned polymer nanofibers that constitute a negative replica of the PVA-lined template. The nanofibers come arranged in a vertical architecture that spans over the surface of the supporting film. Introduction Fused Silica (FS) chips with femtosecond laser micro-patterned surface nanopores are a new and interesting class of hard templates that have been recently used to synthesize arrays of polymer nanofibers [1-4]. While conventional high-quality Anodic Aluminum Oxide (AAO) templates require a four-step preparation process and only offer a close-packed hexagonal arrangement of nanopores that meet the requirements of highly dense structures in the submicrometer range, the FS templates are prepared in a single laser direct-write step that enables user-defined micrometer patterning of nanopores in any desired arrangement [5]. As with AAO templates, FS templates have been used to successfully form extremely long polymer nanofibers that exhibit large aspect ratios. For FS templates, the typical length ranges between 10 and 60 μm, while the aspect ratio can easily reach 200. With up to 25 million nanofibers per square centimeter, FS template-synthesized polymer nanofiber materials exhibit a significantly lower density of fibers, as compared to the materials synthesized using AAO templates. This, combined with the ability to micro-pattern the nanofibers in any user-defined arrangement, affords FS template synthesized materials with structural characteristics that are truly distinct from those exhibited by AAO-synthesized materials. One can thus expect FS template synthesize