# Influence of Solvent Selection in the Electrospraying Process of Polycaprolactone
## 3 Selection of Solvent Systems Used in PCL Electrospraying
### Solution Properties for Tailoring Characteristics of Electrosprayed PCL Particles
#### 3.3.2 Particle Size and Size Distribution
Nevertheless, even if the cone-jet mode is a prerequisite to obtain a monodispersed size distribution of electrospray particles, the ejection of offspring secondary and satellite droplets from primary split ones can lead to an inhomogeneous particle size distribution. The case happens for high electrical solution conductivity with a low viscosity value [95]. Different evaporation process of electrosprayed droplets also results in the different size distribution of final particles. Thus, under lower vapor pressure and viscosity, the quicker evaporation of the solvent and the instability of droplets shape lead to the deformation of electrosprayed droplets during the solidification process, which introduces a \begin{table}
\begin{tabular}{c c c c c} \hline
**PCL Molecular** & **PCL Concentration** & **Solvent Systems** & **Mean Diameter** & **Reference** \\
**Weight (g/mol)** & **(wt.\%)** & **Solvent Systems** & **(\(\upmu\)m)** & **Reference** \\ \hline
14,000 1  & **3.0** & dichloromethane & \(6.81\pm 1.94\) & [147] \\
14,000 1  & 6.0 & dichloromethane & \(16.84\pm 0.88\) & [147] \\
14,000 2  & 3.0 & dichloromethane & \(6.21\pm 1.44\) & [147] \\
14,000 3  & 3.0 & acetonitrile & \(2.25\pm 0.55\) & [147] \\
14,000 4  & 5.0 & tetrahydrofuran & \(7.49\pm 0.08\) & [147] \\
13,000 5 & 5.0 & chloroform & \(57.72\) & [95] \\
13,000 6  & 7.4 & chloroform & \(23.19\pm 4.18\) & [95] \\
13,000 7 8.7 & chloroform & \(20.50\) & [95] \\
13,000 9.6 & chloroform & \(9.73\) & [95] \\
45,000 9.4 & 5.0 & toluene & \(20\) & [126] \\
45,000 1  & 7.0 & toluene & \(50\) & [126] \\
45,000 4  & 120 & [126] \\
10,000 5  & 200 & [126] \\
10,000 6  & 320 & [126] \\ \hline \end{tabular}
\end{table} 
Table 4: Mean diameter of electrosprayed PCL microparticles obtained from different PCL concentration, molecular weight, and solvent systems. non-homogeneous particle size distribution. The choice of the solvent system, with medium vapor pressure and medium viscosity, limits the droplet deformation and reduces the evaporation rate until obtained a narrow particle size. Besides, higher vapor pressure and viscosity lead to a change in the obtained morphology, i.e., beaded fibers when the concentration of the solution or the molecular weight of the polymer used is too high, and particle agglomeration when the evaporation rate is too low are commonly reported. Meanwhile, the use of a co-solvent in the formulation leads to the same phenomena since it induces some modification during the evaporation step [149; 150]. Therefore, the monodispersed particle size distribution is achieved if the solution has low electrical conductivity, moderate boiling point, and medium viscosity values. Also, when the mean diameter of electrospray particles exceeds 100 \(\upmu\)m, it is difficult to recover these particles. Thus, due to the decreasing of the specific surface area resulted from the increase of mean diameter, the evaporation of the solvent in electrospray droplets becomes slow. The presence of residual solvent results in the aggregation and deformation of electrospray droplets or polymeric films.