This article reports a new needleless emulsion electrospinning method for scale-up fabrication of ultrathin core-shell polyacrylonitrile (PAN)/isophorone diisocyanate (IPDI) fibers. These core-shell fibers can be incorporated at the interfaces of polymer composites for interfacial toughening and self-repairing due to polymerization of IPDI triggered by environmental moisture. The electrospinnable PAN/IPDI emulsion was prepared by blending PAN/N, N-dimethylformamide and IPDI/N, N-dimethylformamide solutions (with the solute mass fraction of 1 : 1). The electrospinning setup consisted of a pair of aligned metal wires as spinneret (positive electrode) to infuse the PAN/IPDI emulsion and a rotary metal disk as fiber collector (negative electrode). The formed ultrathin core-shell PAN/IPDI fibers were collected with the diameter in the range from 300 nm to 3 mu m depending on the solution concentration and process parameters. Optical microscopy, scanning electron microscopy, and Fourier transform infrared spectroscopy were used to characterize the core-shell nanostructures. Dependencies of the fiber diameter on the PAN/IPDI concentration, wire spacing, and wire diameter were examined. Results show that needleless emulsion electrospinning provides a feasible low-cost manufacturing technique for scalable, continuous fabrication of core-shell nanofibers for potential applications in self-repairing composites, drug delivery, etc. (C) 2014 Wiley Periodicals, Inc.