4 A novel polyvinylidene fluoride (PVDF) tree-like nanofiber was controllably fabricated via one-step electrospinning by adding certain amount of salt into PVDF solution. A possible mechanism for the formation of the tree-like nanofibers was proposed by analyzing high speed camera photos of the spin jet and the result showed that the formation of tree-like nanofibers was due to the splitting of jets. The effects of salt type, salt content and processing parameter on the content of tree-like branches were investigated. The electrospun nanofibers were characterized by field emission scanning electron microscopy (FE-SEM), energy disperse spectroscopy (EDS), X-ray diffraction (XRD), pore size meter and mechanical properties measurement. It was found that the PVDF/TBAC tree-like nanofibers with improved crystallinity and mechanical strength. The decreased average pore size caused by the tree-like structure and the resistance to organic solvent, can make it as a potential candidate for membrane separation. (C) 2015 Elsevier Ltd. All rights reserved.