## 3 Solvent Effect and Resultant Morphology of PCL  
In order to determine an optimum solvent system for the electrospinning of PCL, different solvents (single and binary solvent systems) were employed with the aim of obtaining bead-free nanofibers. The morphology of PCL electrospinning depends on the type of solvent, electrospinning parameters, concentration of the solvent, concentration of the polymer and the different solvent ratios employed. In the past, chloroform has been the most employed solvent for electrospinning of PCL; this is due to the solubility of PCL in chloroform. [PERSON] and colleagues from Belgium [1] investigated on a suitable solvent system in order to obtain bead-free electrospun polycaprolactone (PCL) nanofibers. In their study, they investigated different single solvents (_viz._: chloroform, formic acid and acetic acid) and binary solvents systems (_viz._: formic acid/ethanol, formic acid/methanol, formic acid/chloroform, acetic acid/ethanol, acetic acid/methanol and formic acid/acetic acid) for the electrospinning of PCL (morphology shown in Figure 3). It was reported that acetic acid as a solvent yielded droplets, whereas formic acid produced a fibrous structure that was composed of droplets (Figure 3c). Chloroform resulted in uniform, but thick fibers in the micro scale rather than fibers in the nanoscale range (Figure 3a). Formic acid/chloroform showed small fibers (500 nm), but there were some noticeable beads in the system (Figure 3a). However, an optimum binary solvent was found for formic acid/acetic acid with nanoscale fibers obtained with few beads. It was concluded that the fibers produced with formic acid/acetic acid (Figure 3e) were more than tenfold smaller than those produced when using chloroform as a solvent for PCL electrospinningning. [PERSON] et al. [37] examined the electrospinningning of polycaprolactone (PCL) nanofibers by using water (H\({}_{2}\)O) as an additive in PCL/glacial acetic acid solution. Water (H\({}_{2}\)O), in this study, was not used as a solvent for PCL electrospinningning, but it was employed for ionization of acetic acid and increases the conductivity. In this study, 17 to 23 wt% of PCL were prepared by dissolving PCL into glacial acetic acid. Optical microscopy (OM) images generally showed coarse features of the fibers, irrespective of the concentration of the solvent. When the concentration of PCL was 17 wt%, large beads with diameters ~15 \(\upmu\)m were obtained with an average diameter of ~211 nm. The authors observed continuous micro scale fibers with the absence of beads at 19 wt% of PCL. When the concentration of PCL was above 19 wt%, thick microfibers with high viscosity were observed. The addition of water (H\({}_{2}\)O) on the fiber morphology was investigated by varying the water volume ratio (_viz._ 3 to 12 vol%), while the concentration of PCL was kept at 17 wt%. For the effect of water on the morphology and diameter, three parameters (viz: solution, process and ambient parameters) were key for electrospinningning. The addition of water (6%) in the PCL/glacial acetic acid (_viz._ 17 wt% of PCL) resulted in spindle-like thick fibers, which were different to the one obtained in the absence of water (large beads). When the concentration of water was increased to 9 and 12%, thick spindle-like fibers with a diameter of ~500 nm were obtained. According to the fiber size histograms reported, it was shown that the frequency of fibers over 500 nm was reduced with the increase in the H\({}_{2}\)O content. The fibers became more uniform when the content of H\({}_{2}\)O reached 9 vol% and above. Based on the morphology, stable solution conditions and the histogram results, the authors concluded that the 9 vol% of water would be the preferred content for ultrafine fiber production under stable conditions of electrospinningning process. The optimum parameters for the production of electrospun PCL nanofibers were investigated [38]. In order to investigate the optimum solvent and PCL concentration, all other parameters were kept fixed.