Conducting nanofiber yarns fabricated by electrospinning

Abstract

Unlike conventional electrospun polymer fibers deposited on a target electrode as a randomly oriented mesh, poly(p-xylenetetrahydrothiophenium chloride) (PXTC), a precursor of poly(p-phenylenevinylene) (PPV), was electrospun into centimeters-long yarns vertically on the surface of the electrode but parallel to the electric field. The formation of the yarn was strongly influenced by the concentration, applied voltage, and relative humidity. The subsequent thermal conversion of thus-electrospun PXTC yarns was carried out at 250°C for 12 h in a vacuum and resulted in the uniaxially aligned PPV nanofibers with an average diameter of 150 nm. The applied voltage increased orientation of PPV nanofibers along the axis of the yarn, while the distribution of fiber diameter was less dependent on the applied voltage. Wide-angle X-ray diffraction analysis indicated that the PPV nanofibers exhibited paracrystalline structure with crystallinity and crystallite size of 45% and 75Å, respectively. Furthermore, doping with sulfuric acid changed the color from yellowish brown to black and brought about a significant increase in the electrical conductivity of the PPV nanofiber yarn.