Electrospinning of polyacrylonitrile nanofibers

Polyacrylonitrile (PAN) was electrospun in dimethylformamide as a function of electric field, solution flow rate, and polymer concentration (C). The fiber diameter, increased With C and ranged from 30 nm to 3.0 mu m. The fiber diameter increased with the flow rate and decreased when the electric field was increased by a change in the working distance; however, it did not change significantly when the electric field was varied by a change in the voltage at a given working distance. The fibers below about 350 nm diameter contained beads, whereas above this diameter, bead-free fibers were obtained. For PAN with a molecular weight of 100,000 g/mol, the fiber diameter. scaled as C-1.2 and C-7.5 at low (5.1-16.1 wt %) and high (17.5-22.1 wt %) C values, respectively. Both concentrations were in the semidilute entangled regime, where. the specific, viscosity scaled as C-4.4, consistent with De Gennes's scaling concepts. In the semidilute unentangled regime (0.5-3.1 wt %), where the viscosity scaled as C-1.3, microscopic or nanoscopic particles rather than fibers were obtained. Concentration-dependent electrospinning studies were also carried out for higher molecular weight PAN (250,000 and 700,00 g/mol). The results of these studies are also presented and discussed. (c) 2006 Wiley Periodicals, Inc.