# Synthesis of Covalently Cross-Linked Colloidosomes from Peroxidized Pickering Emulsions
## 3 Results and Discussion
### Colloidosome Preparation
The obtained results indicate that several morphological characteristics  
Figure 6: Fraction of remaining emulsified oil phase of Pickering emulsions prepared at various pH levels (recorded after a 24 h rest period). of colloidosomes can be controlled by variations in oil phase compositions (e.g., monomer/HD ratio) and the pH levels of the aqueous phase. At the same time, the size of colloidosomes can be adjusted using the pH of the aqueous phase and the homogenization parameters (pulse length, sonication intensity), whereas shell thickness depends on the total initial concentration of monomers. Figure 7 shows SEM images of different colloidosomes (Table 3) synthesized using peroxididized latex particles. Although the surface charge of latex particles is essential for the electrostatic stabilization of droplets in a Pickering emulsion, it can also be disruptive if it is too large. Notably, unlike other samples, the colloidosomes prepared at pH 7.5 did not feature smooth surfaces covered with grafted latex particles. Their outer surfaces showed signs of phase separation during synthesis and an obvious lack of latex particles, which is possibly due to an excessive particle charge at pH 7.5. The same approach was applied for the synthesis of colloidosomes from latex particles synthesized with insiurf PM-1-MAc. The synthetic conditions and characteristics of the formed colloidosomes are summarized in Table 4. \begin{table}
\begin{tabular}{c c c c c c c c c} \hline \hline \multirow{2}{*}{**Colloidosome**} & \multicolumn{3}{c}{**Monomer conc. in**} & \multirow{2}{*}{**Total**} & \multirow{2}{*}{**Monomer/DVB**} & \multirow{2}{*}{**Hexadecane**} & \multirow{2}{*}{**D (um)**} \\  & & **Oil Phase (mol/L)** & & & & & & \\ \cline{2-7}  & **St** & **BA** & **DVB** & & & & & \\ \hline polySt-BA-1 & 1.3 & 0.7 & 2.0 & 4.0 & 1/1 & 1.66 & 4–20 \\ polyBA-2 & – & 2.0 & 2.0 & 4.0 & 1/1 & 1.47 & 5–30 \\ polyBA-3 & – & 1.5 & 1.5 & 3.0 & 1/1 & 1.96 & 10–35 \\ polySt-4 & 3.0 & – & 1.0 & 4.0 & 3/1 & 1.76 & 1.7–6 \\ polySt-5 & 2.0 & – & 2.0 & 4.0 & 1/1 & 1.67 & 6–18 \\ polySt-6 & 2.25 & – & 0.75 & 3.0 & 3/1 & 2.18 & 1–3 \\ \hline \hline \end{tabular}  
* Notes: 1 Ratio of aqueous:oil phase as 9:1; Pickering stabilizer concentration 0.36 wt.%; reaction time 150 min.; temperature 80 \({}^{\circ}\)C.  
\end{table} 
Table 4: Synthetic conditions 1 and properties of colloidosomes based on PM-1-MAc. Figure 7: SEM photographs of colloidosomes synthesized from peroxididized (nisurf PM-2-MAc) latex particles: (**A**) CS2; (**B**) CS3; (**C**) CS1. As determined by SEM measurements, the diameter of the synthesized colloidosomes varied in the range of 1.3 \(\upmu\)m to 35 \(\upmu\)m depending on the synthetic conditions and compositions of the reactive mixture. Figure 8A shows SEM images of colloidosomes polySt-4 (Table 4). The polydispersity of the colloidosome diameter is evidently dependent on a dispersing process during the Pickering emulsion formation; the same behavior was noted in Ref. [20]. The morphology of the synthesized colloidosomes (Figure 8B) clearly shows the presence of the polymer particles within the colloidosome wall. As evidenced by Figure 8C, the colloidosome walls define an internal enclosure, or cavity. The application of divinylbenzene as a low-molecular-weight cross-linker allows for the formation of cross-linked polymers with a three-dimensional structure, namely, the formation of the spongy walls of the colloidosomes (Figure 8C). The cross-linked polymer chains then lose their mobility, which leads to a decrease in their precipitability and an increase in the wall thickness. Under certain conditions, the filling of the entire colloidosome cavity with the spongy polymer was observed (Figure 8D). On the other hand, the development of broken (or not fully formed) colloidosomes was observed when the content of the monomers in the template decreased. This indicates that the walls formed under these conditions are either not strong enough or that the cross-linking degree is low.