Coaxial Electrospinning: Jet Motion, Core–Shell Fiber Morphology, and Structure as a Function of Material Parameters

Two core–shell-structured polystyrene/poly(vinyl pyrrolidone) (PS/PVP) and PVP/PS composite fibers were prepared via coaxial electrospinning in this study. Different concentrations of PVP solutions with a variety of viscosities and conductivities were adopted in the experiment. The influences of both viscosity and conductivity on the Taylor cone, jet motion, morphology, and internal structure of the resultant core–shell fiber were investigated in a comprehensive and systematic manner. As shown in the images of Taylor cone and jet motion, which were captured by a high-speed camera, different PVP concentrations in the core and shell would result in different core and shell thicknesses as well as distinct jet motion patterns including straight jet length, envelop angle, and frequency of whipping process, thus obtaining the core–shell fibers with different diameters. Not only jet motion and Taylor cone but also the polymer solution concentration and the role of PVP in core and shell have a tremendous influence on the morphology and the internal structure of the resultant core–shell fiber. Additionally, the formation mechanisms of PS/PVP and PVP/PS fibers were studied by means of Fourier transform infrared (FTIR). The experimental results provide a basis for further design and optimization of processing conditions, so as to control the nanostructure of core–shell composite fibers.