Electrospun PAN and CA based bicomponent fibers: Nanoporosity and surface features

Ultrathin polyacrylonitrile (PAN) and cellulose acetate (CA) based bicomponent fibers were successfully prepared via electrospinning from solution. Water soluble polymers and oligosaccharide including poly (ethylene oxide) (PEO), poly (vinyl pyrrolidone) (PVP), and beta-cyclodextrin (CD) were selected as second components to mix with the matrix polymers. These second components varied with crystallinity, rigidity of molecular structure and compatibility with matrix polymers. The bicomponent fiber formation as well as fiber size was found to be dependent on both solvent system and polymer system. The parameters of solvent system such as dielectric constant determined the electric stretching force on the polymer jet during electrospinning. The parameters of polymer system such as molecular weight, concentration and bicomponent composition determined the polymer chain entanglement, which must be large enough under certain stretching force to make a continuous polymer jet for uniform fiber formation. The electrospinning should be performed at a balanced condition between polymer molecular entanglement and electric stretching force for uniform fiber formation as well as for desired fiber sizes. The phase separation morphology in bicomponent fibers was governed by polymer pair compatibility, molecular structure and bicomponent composition. Nanoporous, sheath-core, and other heterogeneous fiber structures were obtained from different phase separation morphology plus further selective removal of one component. The enhanced specific surface and structures of these bicomponent fibers will be beneficial to the wide applications of fibrous materials.