Molecular orientation and crystalline structure of aligned electrospun nylon-6 nanofibers: Effect of gap size

We study the effect of the gap size on the molecular orientation and crystalline structure of uniaxially well-aligned nylon-6 nanofibers produced in the gap between negatively charged metal plates. The relative intensities of several absorbance bands are found to be different in the parallel- and perpendicularly polarized FTIR spectra. X-ray analysis indicates that the metastable γ-form is predominant in as-spun nylon-6 nanofibers, and is transformed into the thermodynamically stable α-form by increasing the gap size. The polymer chains are thought to be oriented perpendicular to the fiber direction, and the molecular orientation to the fiber axis is enhanced on increasing the gap size. Polarized FTIR spectroscopy and WAXD of macroscopically well-aligned electrospun nylon-6 nanofibers suggest that the polymer chains are oriented perpendicular to the fiber direction in uniaxially aligned electrospun nylon-6 nanofibers. The degree of molecular orientation relative to the fiber axis was enhanced by increasing the gap size of the collector electrode during electrospinning.