## 3 Results and Discussion
### Mickering Emulsion Stability
In the case of PAMPS-Na, the lowering of emulsion stability with increasing concentrations can be attributed to the formation of non-uniform emulsion particle sizes and the presence of excess PAMPS-Na in water phase (Figure 6c) [42]. \begin{table}
\begin{tabular}{c c c c c c c c c c c} \hline  & \multicolumn{3}{c}{**PAMPS-Na**} & \multicolumn{3}{c}{**PAMPS**} & \multicolumn{3}{c}{**PAAm**} \\ \cline{2-11}
**Time** & **3000** & **1500** & **1000** & **3000** & **1500** & **1000** & **3000** & **1500** & **1000** \\
**(day)** & **mg**\(\cdot\)**L**\({}^{-1}\)** & **mg**\(\cdot\)**L**\({}^{-1}\)** & **mg**\(\cdot\)**L**\({}^{-1}\)** & **mg**\(\cdot\)**L**\({}^{-1}\)** & **mg**\(\cdot\)**L**\({}^{-1}\)** & **mg**\(\cdot\)**L**\({}^{-1}\)** & **mg**\(\cdot\)**L**\({}^{-1}\)** & **mg**\(\cdot\)**L**\({}^{-1}\)** & **mg**\(\cdot\)**L**\({}^{-1}\)** \\ \cline{2-11}  & **Stability** & **Stability** & **Stability** & **Stability** & **Stability** & **Stability** & **Stability** & **Stability** & **Stability** \\  & **\%** & **\%** & **\%** & **\%** & **\%** & **\%** & **\%** & **\%** & **\%** & **\%** \\ \hline \(1\) & 90 & 100 & 100 & 100 & 100 & 100 & 100 & 90 & 86 \\ \hline \(3\) & 77 & 90 & 100 & 100 & 100 & 95 & 100 & 88 & 85 \\ \hline \(7\) & 70 & 87 & 100 & 100 & 100 & 89 & 100 & 83 & 81 \\ \hline \(15\) & 62 & 75 & 100 & 95 & 99 & 75 & 99 & 73 & 71 \\ \hline \(21\) & 62 & 73 & 97 & 93 & 98 & 72 & 95 & 73 & 64 \\ \hline \(30\) & 52 & 70 & 96 & 92 & 95 & 67 & 92 & 68 & 58 \\ \hline \end{tabular}
\end{table} 
Table 1: Stability data of the Mickering emulsions of cyclohexane/water (50:50) stabilized with different concentration of the prepared microgels at 25 \({}^{\circ}\)C and neutral pH. Figure 6: Micrographs of the cyclohexane/water o/w Mickering emulsions (50:50) stabilized by using 1000, 1500, and 3000 mg\(\cdot\)L\({}^{-1}\) of the **(a)** PAAm, **(b)** PAMPS, and **(c)** PAMPS-Na at 25 \({}^{\circ}\)C.  
Figure 7: SEM micrographs of cyclohexane/water (50:50) Mickering emulsions using different concentrations 1000, 1500, and 3000 (mg\(\cdot\)L\({}^{-1}\)) from left to right of **(a)** PAAm, **(b)** PAMPS, and **(c)** PAMPS-Na microgels. The concentrations that gave the higher emulsion stabilities of cyclohexane/water (50: 50) were chosen for PAAm, PAMPS, and PAMPS-Na as 3000, 1500, and 1000 mg\(\cdot\)L\({}^{-1}\) respectively. The pH effect on the emulsions' stability is evaluated and summarized in Table 2. The optical microscope and SEM photos are represented in Figures 8 and 9, respectively. It was previously established that [9; 20; 23; 30; 31] the Pickering stable emulsion increased with increasing pH due to the swelling increase of microgel particles and the emulsion stability reduced with the pH lowering due to flocculation of the microgel particle. In the present work, the stability data, shown in Table 2, elucidate that both PAMPS-Na and PAAm achieved excellent stability with increasing the pH from 4 to 9, while the PAMPS microgel has good emulsion stability at pH 4 and its stability reduced with increasing pHs of aqueous solution. It is expected that the NH\({}_{2}\) of the PAAm microgel would gradually hydrolyze to carboxylate in the alkaline solution, which introduced charges to the microgels and affect the adsorption behavior at the oil-water interfaces. A pale emulsion phase was observed at pH 9 that was not stable at room temperature for two days after preparation (Figure 8). The PAAm microgels shrunk and degraded in acidic solutions and led to an unstable Mickering emulsion due to the low coverage of microgels at the oil-water interfaces (Figure 8a). However, the degradation of microgels in the acid solution was a slow process, and the volume of emulsion phase and the average oil drop diameter did not show significant changes in seven days (Table 2). The architecture of adsorbed microgel layers was controlled by the pH of the Mickering emulsions.