Optimizing the Ecovio® and Ecovio®/zein solution parameters to achieve electrospinnability and provide thin fibers

Abstract The electrospinning of polymer solutions has received great notoriety for promoting thin fibers. However, it is challenging to modulate the solution parameters (polymer system, polymer concentration, solvent type, electrical conductivity, and viscosity) to create homogeneous and beaded-free fibers with diameters lower than 200 nm. Here, we performed solubility tests of Ecovio® and zein in chloroform, dichloromethane, N,N-dimethylformamide, ethanol, and binary mixtures of these solvents. The best solvent pair to create Ecovio®/zein blends is dichloromethane/formic acid mixtures. We optimize the solution parameters to electrospun Ecovio®/zein blends, using factorial designs. The electrical conductivity increases from 28.76 to 37.58 μS cm−1 as the zein concentration rises from 20 to 30 wt% in the blend at 10% wt/vol Ecovio® + zein and 80/20 dichloromethane/formic acid volume ratio. At 10% wt/vol Ecovio® + zein and 80/20 dichloromethane/formic acid volume ratio, the solution viscosity reduces from 12.4 ± 0.2 to 9.3 ± 0.1 mPa·s as the zein level rises from 20 to 30 wt% in the blend. Suitable zein contents (20–45 wt%) in Ecovio®/zein blends at 10, 11, and 12% wt/vol (Ecovio® + zein) at binary dichloromethane/formic acid mixtures (ratios between 70/30 and 90/10 vol/vol) support electrospinnability. We adjust the electrical conductivity and viscosity by tuning the zein and formic acid contents in the blends. Bead-free Ecovio®/zein fibers (117 ± 53 nm) were created at 35 wt% zein concentration and 80/20 dichloromethane/formic acid volume ratio. The materials were characterized by scanning electron microscopy, energy-dispersive X-ray spectroscopy, and infrared spectroscopy. We create Ecovio®/zein fibers by electrospinning blends for the first time.