## 3 Results and Discussion
### Mickering Emulsion Stability  
The emulsion stability of oil-in-water (O/W) cyclohexane/water (50:50 Vol. %) using PAAm, PAMPS, and PAMPS-Na as stabilizers is investigated as represented in the experimental section to select the optimum conditions such as microgel concentrations, pH, temperature, salt content, and emulsion composition. The optimum conditions were determined for the polymerization of styrene or 4-vinylpyridine using the formed Mickering emulsion. The rate at which an emulsion creans, flocculates, or coalesces is used to determine the emulsion stability. The PAAm, PAMPS, and PAMPS-Na microgel concentrations range from 1000 to 3000 mg\(\cdot\)L\({}^{-1}\). The concentration change had remarkable influence on the Mickering emulsion stability and the emulsion average droplet size. The emulsion stability data of cyclohexane/water with volume fraction (50:50) using different concentrations of PAAm, PAMPS, and PAMPS-Na are evaluated and summarized in Table 1. The micrographs of Mickering emulsions and the average diameter results of oil drops are shown in Figure 6a-c. The emulsified oil drops were also investigated using SEM micrographs (Figure 7a-c). It was noticed that the increase of microgel concentrations within a certain range resulted in an increase in the total surface area of microgel adsorbed at the oil-water interfaces, which facilitated the formation of Mickering emulsions with smaller oil drop. The emulsified oil drops were no longer spherical and turned to agglomerate with each other when the microgel concentration was below 1500 mg\(\cdot\)L\({}^{-1}\). No separated oil phase was observed when the PAAm concentration was higher than 1500 mg\(\cdot\)L\({}^{-1}\). The thickness of PAAm surrounded the emulsion droplets increases with increasing the PAAm concentrations. The dispersed PAAm microgels promisingly formed interparticle structures through polymer chain entanglement that resulted in the heterogeneous shape of oil drops (Figure 7a). As expected, the uniform spherical emulsion droplets with the reduced average diameter became constant at PAMPS and PAMPS-Na concentrations reached 1500 mg\(\cdot\)L\({}^{-1}\) (Figure 6b,c). At the high PAMPS and PAMPS-Na concentrations, a large amount of microgels remained in the water phases as well as being adsorbed at the oil-water interfaces. When the PAMPS and PAMPS-Na concentrations were between 1000 and 3000 mg\(\cdot\)L\({}^{-1}\), the microgels adsorbed at the oil-water interfaces formed a shielding layer as well as aggregate, and formed string-like structures to stabilize oil drops. When the microgel concentration was above 1500 mg\(\cdot\)L\({}^{-1}\), the string-like structures of microgels further grew into planar structures that prevented the coalescence of oil drops through steric hindrance. The uniform spherical morphologies of PAMPS-Na microgel (TEM micrograph; Figure 3c) and lower particle sizes (Figure 4c) are responsible for producing more self-assembled PAMPS-Na microgels on the surface of cyclohexane drops at a lower concentration than PAAm or PAMPS. The migration of microgels from their aqueous dispersion and deformation of microgels at the oil-water interface reduced the surface energy of an emulsion system to increase the emulsion stability [16]. The effect of storage times on the stability of the prepared Mickering emulsions using different concentrations of PAAm, PAMPS, and PAMPS-Na (Table 1) elucidate that the 3000, 1500, and 1000 mg\(\cdot\)L\({}^{-1}\), respectively, are suitable to obtain stable cyclohexane/water emulsion for 30 days at room temperature. The increase in emulsion stability with increasing concentrations of PAAm and PAMPS can be attributed to the multilayer adsorption of nonionic microgel particles on the emulsion droplet with the formation of networks [42]. It was observed that the stability of Mickering emulsions increases with increasing the coverage and the strength of adsorbed layer of microgel particles at the cyclohexane/water interface (Figure 6a,b).