An investigation of structural changes in modified and oxidized PAN nanofibers using different concentrations of KMnO4 solutions

PAN nanofiber was prepared by electrospinning process using 15wt% acrylonitrile, methyl acrylate and methyl allyl sulfonate terpolymers as precursors and DMF as solvent. Produced PAN nanofiber was modified by applying different concentrations of KMnO4 aqueous solutions from 1, 3, 5, and 8wt%. Then, the modified nanofibers were further oxidized under O2 at 250oC for 60 minutes. The average fiber diameters of modified and oxidized nanofibers were decreased from 377nm to 220nm and 480nm to 184nm respectively as a result of increasing KMnO4 concentrations. KMnO4 and methyl acrylate as precursor were accelerated the preoxidation and cyclization rates while reduced the time of thermal stabilization. The modified nanofibers have shown good hydrophilicity at higher concentrations of KMn04.The structures and properties of modified and oxidized PAN nanofibers at various concentrations were characterized by Fourier transform infrared spectroscopy and scanning electron microscopy. According to the obtained FT-IR results, KMn04 oxidized and transformed groups to ones; which is also proved by variation in the color of modified specimens from white to light yellow, dark yellow and ultimately brown, with the increase of KMn04 concentrations at a constant treatment time. Moreover, FT-IR results have shown that the peak intensities of O-H groups were significantly increased when PAN nanofibers treated by different concentrations of KMnO4 and more functional groups produced as well. However, in the oxidized PAN nanofibers, the peak intensities of groups are intensively diminished in comparison with modified ones while no significant variations were observed in the peak intensities of O-H groups in this case. On the other hand, it could be concluded that the cyclization process is more dominate than the oxidation process in the oxidized PAN nanofibers. The SEM images indicate that the loading of higher concentrations induced to grow KMnO4 crystals on the surface of the modified nanofibers

Keywords:

PAN Nanofiber , KMn04 Concentration , Modification , Terpolymer , FT-IR , Oxidized