Effect of successive electrospinning and the strength of hydrogen bond on the morphology of electrospun nylon-6 nanofibers

We demonstrate for the first time herein that the successive electrospinning can change the fiber morphology in the electrospun mat of the polymer at the same electrospinning parameters. Two types of fibers (nano and sub-nano size) arranged in a spider-net like structure were obtained from the single polymer nylon-6 by electrospinning. FE-SEM images of the mats at different applied voltage showed that this network consisted of thin nanofibers with diameters of about 8–29 nm and thick nanofibers with diameters of about 80–292 nm, arranged in a spider-net like structure. The successive electrospinning sufficiently decreased the diameter of the main nanofibers and hardly change the diameter of the thinner fibers. The study of FT-IR spectra and the conductivity of the different mats in acidic solution showed that the formations of spider-net structure were due to the formation of stronger hydrogen bonds between ionized oligomer/monomer and polymer molecules. The possible mechanism of hydrogen bonds formation during electrospinning was proposed. These spider-net structures with high aspect ratio were responsible to increase the mechanical strength of nylon-6 mat.