# Influence of Solvent Selection in the Electrospraying Process of Polycaprolactone
## 4 The Effect of Operating Parameters and Solution Properties in PCL Electrospraying
\begin{table}
\begin{tabular}{c c c c c c c c c c} \hline \hline
**PCL** & & & & & & & & & \\
**Molecular** & & & & & & & & & \\
**Weight** & & & & & & & & & \\
**(g/mol)** & & & & & & & & & \\ \hline
45,000 & toluene & 5 & 11–18.5 & 20–50 & 5 & - & 26.5 & 3.0 & [126] \\
45,000 & toluene & 7 & 10–18.5 & 20–50 & 5 & - & 28.0 & 6.7 & [126] \\
45,000 & toluene & 10 & 12–18 & 20–50 & 5 & - & 28.5 & 11 & [126] \\
10,000 & toluene & 15 & 10–13 & 20–50 & 5 & - & 28.4 & 6.0 & [126] \\
10,000 & toluene & 20 & 7–72.8 & 20–50 & 5 & - & 29.6 & 16 & [126] \\
10,000 & toluene & 25 & 8–512.8 & 20–50 & 5 & - & 32.8 & 25 & [126] \\
14,000 & dimethylacetamide & 2 & 7–10.5 & 2–50 & 2 & 3.4 & 29 & 2.6 & [127] \\
14,000 & dimethylacetamide & 5 & 9–01-45 & 2–50 & 2 & 1.8 & 29 & 4.6 & [127] \\
14,000 & dimethylacetamide & 10 & 9–5-15 & 2–50 & 2 & 0.8 & 32 & 11.1 & [127] \\
43,000–50,000 & methanol/chloroform & 1.5 & 12 & 16.67 & 12 & 0.02 & - & 2.4 & [128] \\
37 & & & & & & & & & \\
45,000 & dichloromethane & 3 & 9–12 & 25 & 10 & 1.0 & 24.7 & 6.3 & [129] \\
45,000 & dichloromethane & 8 & 11–14 & 50 & 10 & 1.0 & 27.5 & 12.3 & [129] \\
45,000 & dichloromethane & 6 & 6.9–7.9 & 50 & 5-30 & 1.0 & 24.7 & 6.3 & [130] \\
43,000–50,000 & chloroform & 1.5 & 8 & 16.67 & 12 & - & - & - & [129] \\
50,000 & chloroform & 9 & 10 & 8.33 & 25 & - & - & - & [92] \\
45,000 & chloroform & 9 & 7.5 & 5 & 10 & - & - & - & [98] \\ \hline \hline \end{tabular}
\end{table} 
Table 5: Operating parameters value ranges to achieve cone-jet mode in the electrospraying process of PCL. distance is privileged to generate a higher electric field strength leading to the formation of smaller particles. Nevertheless, insufficient time to allow solvent evaporation may induce coalescence and aggregation of the particles at the surface of the collector. On the other hand, a longer working distance requires the use of higher applied voltage to compensate the lower electric field strength [62]. In this context, this distance may lead to lower yield due to material loss to the surrounding environment with the presence of turbulence during the droplet flight. Nevertheless, a long working distance is required to obtain denser polymer particles, since it allows the complete solvent evaporation and diffusion before reaching the collector surface. Furthermore, it is usually smaller for the low conductive solution and increases when the electrical conductivity increases to improve the stability of the cone-jet mode. The working distance range applied for PCL particle production is set between several centimeters up to 20 cm, and more especially from 3 to 15 cm (Table 5). Three cm is the lower limit allowing the creation of the electrical discharge in the system [62]. For working distance higher than 15 cm, the intensity of the electric field weakens, and the forces generated are too low to compensate the surface tension and viscoelastic force. Therefore, a long working distance is preconized for high conductivity, and low vapor saturated pressure solutions. Also, the formation of the cone-jet mode for high surface tension or high viscous solutions requires small working distance in the electrospray process. Besides, the working distance between the nozzle tip and the collector also affects the structure and morphology of the particles. Thus, high working distance leads to a decrease in the electric field, which increases the mean diameter of the particles. One the other hand, there is a trend to achieve smaller particles under low working distance based on an increase of the voltage. However, an incomplete solvent removal during the flying process leads to an increase of the particles size as well as a widening distribution. Thus, the swelled particles may be deformed and coalesce at the surface of the collector. As the working distance increases, the particle size distribution becomes narrow with a monomodal distribution induced by the complete evaporation of the solvent and the homogeneous break-up of the charged droplets, and the particles are spherical [98; 160].