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Keywords:

  • birefringence;
  • electrospinning;
  • fibers;
  • orientation;
  • zein

Abstract

Thumbnail image of graphical abstract

Zein fibers have been produced by electrospinning from acetic acid, aqueous methanol, ethanol and isopropyl alcohol. Alcohol solutions produced fibers that were predominantly ribbons. Fibers spun from acetic acid solution have a round morphology with a narrower distribution of diameters when spun under suitable conditions. The IR spectra of electrospun fibers display increased absorbance at 1 650 cm−1 relative to starting material, indicative of increased α-helical structure. Raman spectra of fibers spun from acetic acid solution had spectral differences, having increased absorbance at 680, 750 and 860 cm−1, versus fibers spun from alcoholic solvents suggesting different tertiary structure within the fiber, which may result from different structures in solution. Polarized Raman spectroscopy taken parallel and perpendicular to the fiber axis displayed no differences, suggesting similar secondary and tertiary structures in these directions. All of the fibers had some degree of birefringence demonstrating the presence of orientation. The smaller fibers were highly birefringent throughout the fiber, while the larger fibers had orientation at the surface only. Quality fibers could not be produced from N,N-dimethylformamide, acetone/water, acetic acid/water, 8 M urea/water or 10% NaOH/water zein solutions.