## 3 Results and Discussion
### Preparation of PS Microsphere Using PAMPS Microgel  
Styrene and 4-vinyl pyridine are two water insoluble monomers. The water/PS or water/P4 VP systems used in the presence of PAMPS to form a stable emulsion utilized for emulsion polymerization of the system and to prepare polystyrene PS and P4-VP nanospheres. PAMPS concentration (1500 mg-L\({}^{-1}\)) microgel was selected based on Mickering stability data to polymerize PS and P4-VP microgels as represented in the experimental section. The chemical structure of PS/PAMPS and P4-VP/PAMPS nanospheres is confirmed by FTIR spectra summarized in Figure 11a,b. The appearance of bands at 3462, 1644-1697, 1400, and 1043 cm\({}^{-1}\), which referred to NH stretching, CONH, S=O asymmetric stretching, and symmetric S=O stretching, elucidates the contribution of PAMPS in the chemical structure of PS/PAMPS and P4-VP/PAMPS microgels (Figure 12a,b). The new bands at 3026, 1596, 755, and 696 cm\({}^{-1}\) are characteristics of =CH, C=C stretching, and C=C out-of-plane bending, respectively (Figures 11a and 12b) and elucidate the presence of polystyrene and polyvinyl pyridine, verifying the as-synthesized composites are made up of PAMPS with PS/PAMPS and P4-VP/PAMPS. The thermal characteristics of PS/PAMPS and P4-VP/PAMPS microgels were evaluated using DSC thermograms as represented in Figure 12a,b. The first run of PS/PAMPS microgel (Figure 13a) gave endothermal peak, which disappeared after quenching in runs 2 and 3. That is attributed to macromolecular packing of PS chains [45; 46]. It is noticed that only one glass transition value, Tg, of PS appeared at 85.35 \({}^{\circ}\)C (Figure 13a) and elucidated the compatibility of PS with PAMPS or the formation of microgel composite. The Tg value reduced than reported for crosslinked PS [46] and more than Tg of PAMPS [47] to confirm the elasticity of the prepared PS microgel prepared by using PAMPS using Mickering emulsion technique. By comparing the Tg value of the crosslinked P4-VP [48] with that prepared in this study, it was found that the P4-VP/PAMPS microgel has Tg at 142.23 \({}^{\circ}\)C (Figure 12b), which is the same as reported for Tg of P4-VP. This means that the PAMPS produces more crosslinked and rigid P4-VP chains. Figure 11: FTIR spectra of (**a**) PS/PAMPS and (**b**) P4-VP/PAMPS microgels. Figure 12: DSC thermograms of (**a**) PS/PAMPS and (**b**) P4-VP/PAMPS microgels. The TEM images of PS/PAMPS and P4-VP/PAMPS, shown in Figure 13a,b, are used to investigate the morphology of the produced microgels. It is clearly visible that the PAMPS particles are located at the surface of the PS microgel with spherical morphology (Figure 13a). The rugged surface morphology in Figure 13a clearly indicates that the PS microgel is covered by layer has different sizes of PAMPS. The TEM image of P4-VP (Figure 14b) shows non-uniform rough spherical particles without coating with PAMPS to elucidate the DSC data (Figure 12a,b). Figure 14: Dynamic light scattering (DLS) data of PS/PAMPS microgel at pH (a) 4, (b) 7, and (c) 10 in aqueous solution at room temperature. Figure 13: TEM micrographs of (**a**) PS/PAMPS and (**b**) P4-VP/PAMPS microgels. The pH sensitivity of the prepared PS/PAMPS and P4-VP/PAMPS can be evaluated from the variation of their zeta potential (surface charges) and particle sizes at different pHs using DLS data represented in Figures 14 and 15a-c.  
By comparing the DLS data of PAMPS (Figures 4b and 5b) with the data represented for PS/PAMPS (Figure 14a-c), it is observed that the surface charges and hydrodynamic diameters of PS/PAMPS microgel composite slightly increased compared to the PAMPS microgel at different pH. Moreover, the PDI values of PS/PAMPS microgel are reduced compared to that for PAMPS microgel to indicate the formation of uniform stabilized PS core and PAMPS shell as microgel composites. The DLS data of P4-VP/PAMPS (Figure 15a-c) elucidate its pH sensitivity as confirmed by the positive and negative surface charges in acidic and basic solutions, respectively.