## 3 Results and Discussion
### Mickering Emulsion Stability
As shown in the SEM pictures, the PAAm and PAMPS-Na microgel shrunk and aggregate with each other under acid conditions (at pH 4) (Figure 9a,c) due to deionization of sulfonate and protonation of amide groups of PAMPS-Na and PAAm. The formation of network or clusters at pH 9 for PAMPS-Na displayed higher elasticity to increase the stability of Mickering emulsion [27]. The bowl-shaped coverage of deformed microgels at the oil/water interface was observed at pH from 7 to 9. The PAMPS show that dense packing of microgel particles at pH 9 (Figure 9b) would lead to brittle interfaces that destabilize the emulsion [9; 20; 23; 30; 31]. Finally, it can be concluded that, the Mickering emulsions can be easily destabilized on demand by altering the pH. \begin{table}
\begin{tabular}{c c c c c c c c c c} \hline \multirow{3}{*}{
\begin{tabular}{c} **Time** \\ **(day)** \\ \end{tabular} } & \multicolumn{8}{c}{**Emulsion Stability Data at Different pH**} \\ \cline{2-10}  & \multicolumn{3}{c}{**7**} & \multicolumn{3}{c}{**4**} & \multicolumn{3}{c}{**9**} \\ \cline{2-10}  & **PAMPS-Na** & **PAMPS** & **PAAm** & **PAMPS-Na** & **PAMPS** & **PAAm** & **PAMPS-Na** & **PAMPS** & **PAAm** \\ \hline
1 & 100 & 100 & 100 & 80 & 100 & 81 & 100 & 50 & 73 \\ \hline
3 & 100 & 72.5 & 100 & 72 & 100 & 72 & 99 & 50 & 66 \\ \hline
7 & 100 & 72 & 100 & 68 & 98 & 68 & 82 & 0 & 65 \\ \hline
15 & 99 & 72 & 98 & 63.5 & 98 & 62 & 77 & 0 & 65 \\ \hline
21 & 98 & 72 & 95 & 57 & 97 & 54 & 72 & 0 & 63 \\ \hline
30 & 96 & 64 & 90 & 46 & 93 & 48 & 64 & 0 & 62 \\ \hline \end{tabular}
\end{table} 
Table 2: Emulsion stability data of cyclohexane/water (50:50) in the presence of 1000, 1500, and 3000 mg\(\cdot\)L\({}^{-1}\) of PAMPS-Na, PAMPS, and PAAm microgels. The as-prepared Mickering emulsions were incubated at temperatures ranging from 30 to 60 \({}^{\circ}\)C for 30 min and were then left to stand at room temperature after which the stability data and the mean diameter of droplets were measured at day 7. The emulsion stability data are recorded and summarized in Table 3. The optical microscope photos of PAAm (3000 mg:L\({}^{-1}\)), PAMPS (1500 mg:L\({}^{-1}\)),  
Figure 8: Optical microscope micrographs of cyclohexane/water (50:50) Mickering emulsions using pHs 4, 7, and 9 from left to right of **(a)** PAAm (3000 mg:L\({}^{-1}\)), **(b)** PAMPS (1500 mg:L\({}^{-1}\)), and (c) PAMPS-Na (1000 mg:L\({}^{-1}\)) microgels. Figure 9: SEM micrographs of cyclohexane/water (50:50) Mickering emulsions using pHs 4, 7, and 9 from left to right of **(a)** PAAm (3000 mg:L\({}^{-1}\)), **(b)** PAMPS (1500 mg:L\({}^{-1}\)), and **(c)** PAMPS-Na (1000 mg:L\({}^{-1}\)) microgels. and PAMPS-Na (1000 mg\(\cdot\)L\({}^{-1}\)) at a temperature range of 35 to 55 \({}^{\circ}\)C are represented in Figure 10a-c. The data, listed in Table 3 and Figure 10a-c, elucidate that the Mickering emulsions based on PAMPS-Na are more stable up to a temperature of 55 \({}^{\circ}\)C than PAMPS, which are more stabilized than PAAm. Figure 10a confirms that the sizes of emulsion droplets increase by increasing the temperature and small emulsion droplets loss the surrounded PAAm layer. These observations can be attributed to the increase in Brownian motion of PAAm due to weak hydrogen bond between amide groups of PAAm and water with increase in temperature and so their kinetic energy is increased i.e., by \(\sim\)1.2 times from 20 to 90 \({}^{\circ}\)C. Brownian motion results in the redistribution of particles onto the interface [43] and may also promote desorption of the PAAm particles. This may lead to exposure of the droplets surfaces and thus increase the tendency to coalesce. Furthermore, the increase in temperature could lead to an in increase in the kinetic energy of the droplets, thus promoting collisions and coalescence events. The PAMPS and PAMPS-Na (Figure 10b,c) microgels show great stability without changes in the particles sizes with increasing the temperature.