Continuous bundles of aligned electrospun polyacrylonitrile copolymer nanofibers prepared via the flowing water bath and their morphological, structural, and componential variations during the opposite-directional diffusion process

Continuous bundles of aligned electrospun polyacrylonitrile (PAN) copolymer nanofibers were prepared via collection with flowing water at varied temperatures. The morphological and structural properties, as well as the density and residual solvent amount, of electrospun nanofibers in different bundles were investigated. The results indicated that with the increase of water temperature, both diffusion coefficients of solvent (i.e., N,N-dimethylformamide) and non-solvent (i.e., H2O) increased; the surface roughness of nanofibers also increased, and the cross-section of electrospun nanofibers changed in shape from circular to irregular. With the decrease of water temperature from 25 to 2 °C, the average radius of gyration value (related to the average size of micro-voids in the nanofibers) decreased from 10.9 to 6.8 nm, the crystallinity value increased from 54.6% to 57.9%, and the nanofiber density increased from 1.191 to 1.202 g/cm3. It is envisioned that the continuous bundles of aligned electrospun PAN copolymer nanofibers collected with the flowing water bath at a low temperature (e.g., 2 °C) might be an innovative type of precursor for making the carbon nanofibers with superior mechanical strength.