Electrospinning of Concentrated Polymer Solutions

A modified coaxial electrospinning process, in which an unspinnable concentrated polymer solution acted as a guide and a pure solvent was used as sheath fluid to facilitate the process and thin the fibers, was reported. Polyvinylpyrrolidone (PVP) and Eudragit L100 are used as model polymers for the modified process. A 35% w/v concentrated (PVP) solution prepared in anhydrous ethanol was used as core fluid at a fixed flowrate of 1.0mL/h. The sheath fluid, N,N-dimethylacetamide (DMAc), was used at flow rates 0.1, 0.2, 0.5, and 1.0 mL/h. 27% and 30% w/v solutions of E-L100 were prepared in anhydrous ethanol. The sheath solvent flow rate was fixed at 0.5 mL/h. Ethanol, DMAc, and a 70:30 volume ratio mixture was used as sheath fluids. A double syringe pump was used for driving the concentrated polymer solutions and the surrounding solvent synchronously. The results showed that the fibers prepared using DMAc as sheath solvent had a smooth surface and very small diameter of 450 ± 310 nm but a wide diameter distribution.