## 3 Results
### Fabrication of the NPs  
The influence of various factors on the fabrication of the NPs via nanoprecipitation was studied. The NPs were prepared according to the general procedure described in Section 2 above (see Materials and Methods).  
\begin{table}
\begin{tabular}{c c c c c} \hline \hline
**Polymer** & **Class of the Polymers** & \(M_{w}\) & \(M_{w}\) & \(M_{w}/M_{w}\) \\ \hline
**1F6** & PEU & 35,400 & 20,500 & 1.73 \\
**1L6** & PEU & 90,400 & 54,100 & 1.67 \\
**4F4** & PEA & 66,400 & 47,400 & 1.43 \\
**8L6** & PEA & 46,500 & 23,400 & 1.98 \\
**8R6** & PEA & 17,500 & 7,200 & 2.43 \\ \hline \hline \end{tabular}
\end{table}
Table 1: MW characteristics of the AABB polymers used for fabricating the NPs.  
\begin{table}
\begin{tabular}{c c c c c} \hline \hline \multirow{2}{*}{**Polymer**} & \multicolumn{3}{c}{**Solubility of 10 mg of Polymer in 1 mL of the Solvent \({}^{*}\)**} \\ \cline{2-5}  & **DMI** & **DMSO** & **DMF** & **Acetone** \\ \hline
**1F6** & +t & +t & +t & - \\
**1L6** & + & + & + & + \\
**4F4** & + & + & + & - \\
**8L6** & + & + & + & + \\ \hline \hline \multicolumn{5}{c}{\({}^{*}\) + soluble at r.t., - insoluble at r.t., +t soluble on heating up to 50 \({}^{\circ}\)C.} \\ \end{tabular}
\end{table}
Table 2: Solubility of the PEAs and PEUs in organic solvents.  
3.1 The Influence of a Polymer Concentration in the Organic Phase in the Presence of Various Surfactants in the Water Phase  
In these experiments two neutral AABB polymers **1F6** and **4F4** and all eight surfactants were used. The parameters (invariable and variable) of the NPs fabrication process are given in the table below:  
\begin{tabular}{c c c} \hline \hline \multicolumn{3}{c}{**Parameters of the Process**} \\ \hline \multicolumn{3}{c}{**Invariable**} & \multicolumn{2}{c}{**Variable**} \\ \hline \(\bullet\) & solvent—DMI & \(\bullet\) & polymers (two)—**1L6** and **4F4** \\ \(\bullet\) & concentration of a surfactant in water phase—5 mg/mL & \(\bullet\) & concentrations of a polymer in the organic phase—0.6, 3.0 and 6.0 mg/mL \\ \(\bullet\) & O/W ratio—1:10 & \(\bullet\) & surfactants (eight)—Tween 20, Tween 40, Tween 80, Triton X-100, Kolliphor P188, \\ \(\bullet\) & stirring rate of the water phase—700 rpm & \(\bullet\) & Brij 010, Mowiol 4-88, and Mowiol 8-88 \\ \hline \hline \end{tabular}  
The conditions of the NPs' fabrication were as follows: The solvent: DMI; polymer concentration in the organic phase: 0.6, 3.0, or 6.0 mg/mL; surfactant concentration in the water phase: 5 mg/mL; the O/W ratio: 1:10; the organic phase dropping rate: 12 drops/min; and the stirring rate of the water phase: 700 rpm.  
The results obtained for the selected AABB polymers **1F6** and **4F4** using all eight surfactants in terms of the mean diameters of the NPs are given schematically in Figures 3 and 4.  
Figure 4: The influence of the polymer concentration in the organic phase on the formation of the **4F4** NPs in the presence of various surfactants in the water phase.  
Figure 3: The influence of the polymer concentration in the organic phase on the formation of the **1F6** NPs in the presence of various surfactants in the water phase.  
When the polymers were precipitated in pure water (free of surfactants) full aggregation of the NPs was observed at all the concentrations used (Table 3).