Potential fabrication of core–shell electrospun nanofibers from a two-step method: Electrospinning and photopolymerization

Fluoride compounds could migrate to the surface in a blending solution because of their low surface energy. In order to prepare a photo-sensitive nanofiber, a diphenyl-ketone photoinitiator with a fluorinated aliphatic chain was synthesized, and its structure was characterized using 1H NMR and 19F NMR, UV–vis absorbance spectroscopy, and fourier transform infrared (FT-IR). A blending solution of polyacrylonitrile (PAN) and photoinitiator containing fluorine with dimethylformamide (DMF) as the solvent was electrospun to prepare a photo-sensitive nanofiber. The photo-sensitive nanofiber was used to fabricate a polymer brush grafted on the nanofiber by initiating the polymerization of tripropylene glycol diacrylate (TPGDA) and hydroxyethyl acrylate (HEA) monomers via UV irradiation. The distribution of the photoinitiator on the surface of the nanofibers before and after photopolymerization was measured using UV–vis absorbance spectroscopy. The kinetics of the photopolymerization of TPGDA and HEA monomers on the surface of the nanofibers was studied using real-time infrared spectroscopy (RT-IR). The size and morphology of the nanofibers were investigated using scanning electron microscopy (SEM). The internal core–shell structure and the surface composition of nanofibers were further studied using transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), and attenuated total reflectance-infrared spectroscopy (ATR-IR). It was suggested that the photoinitiator on the nanofiber surface could cause the polymerization of the TPGDA and HEA monomers under UV irradiation. The solubility of the nanofibers polymerized with TPGDA on the surface was also investigated in water, DMF and acetone. The experimental results indicated that the nanofiber was enriched with the photoinitiator on its surface and that the nanofiber had potential for application in the preparation of functional core–shell nanofibers.