The morphology regulation of nanofiber (NF) plays an important role in its applications. In the present study, a simple method to tailor the cross-section morphology of polyvinylidene fluoride (PVDF) NFs by controlling the interfacial diffusion during coaxial electrospinning is presented. By choosing a soft bad-solvent of PVDF to prepare a partially miscible inner solution, the regulation of the interfacial diffusion can be simplified into the adjustment of the viscosity difference between the inner and outer solutions. When the viscosity of the inner solution surpassed that of the outer solution, the diffusion direction changed from outer-to-inner to inner-to-outer, which leaded to the change in the cross-section morphology of resultant NFs from a net-like to a hollow structure. Water contact angle also showed the effect caused by the interfacial diffusion. BET surface area of the as-prepared porous PVDF NFs can reach up to 42 m(2)/g, which is almost the highest data ever reported in the literature for polymer nanofiber. (C) 2016 Elsevier Ltd. All rights reserved.