Biopolymers

Random and highly aligned bead-free chitosan nanofibers (NFs)were successfully prepared via electrospinning by keeping the applied voltage (22 kV), flow rate (0.4 mL h-1), needle diameter (0.8 mm), and needle to collector distance (100 mm) constant while varying the solution concentration and collector rotation speed. No electrospinning was observed for lower solution concentrations, i.e., 1-3 wt% (w/v), whereas a decrease in the number and size of beads and microspheres, and bead-free NFs were obtained when the concentration of solution was increased from 4 to 6 wt%. Increase in the polymer concentration increased the solution viscosity (from 3.53 to 243 mPa s) and conductivity (from 29.80 to 192.00 μs cm-1) to critical values, which led to beadless NFs. The optimized conditions (i.e., concentration of solution 6 wt. %, applied electrical potential 22 kV, flow rate 0.4 mL h-1, needle diameter 0.8 mm, and needle to collector distance 100 mm) were further used for the alignment of chitosan NFs. The alignment of the NFs increased from 3 to 94.4 % and the diameter decreased from 163.9 to 137.4 nm as the rotation speed of the cylindrical collector drum was increased from 2.09 to 21.98 m s-1. The aligned and small diameter chitosan NFs might find potential applications in biomedical, environmental, solar fuel cell applications, etc. Several target devices and polymer systems in the literature have been used to obtain aligned NFs; however, almost no work has been reported on individual chitosan alignment.