## 1 Introduction  
It is recognized that the emulsion polymerization produced advanced polymeric materials, but it is limited for the producing of nano-polymeric materials due to the requirement of relatively large number of surfactants [1]. Moreover, toxicity, foaming, recycling high cost, and the removal of surfactants after polymerization are rather tedious. The using of solid nano- or micro-particles added new types of very stable emulsions termed Pickering or Mickering emulsion [2]. Pickering emulsions use solid particles with rigid structures and stable dispersions at different pHs in aqueous system (modified silica, montmorillonite platelets, modified and nano-ZnO) [3; 4; 5; 6; 7], while the soft gel particles are used to produce stable Mickering aqueous and non-aqueous emulsions. The solid colloidal particles can efficiently act as emulsifiers. The adsorption of particles with the correct wettability at the liquid-liquid interface leads to the formation of a stable emulsion. The stability of this kind of emulsion can be higher than that of the conventional emulsion. This efficiency stems from the higher energy required to remove one particle from the interface [8; 9; 10; 11]. The amphiphilic soft microgels with stimuli-responsive properties are used to produce controllable advanced nanomaterials and smart emulsions. These emulsions are applied in food, cosmetics, pharmacy, and petroleum industries, and enzyme catalysis [12; 13; 14; 15; 16; 17; 18; 19; 20; 21; 22]. The mechanism to illustrate the emulsion stability using soft gel particlesis still under debate. One of the suggested mechanisms depends on the ability of soft gel particle to respond to the surrounding environments. It is proposed that the gel particles could assemble or adsorb at the fluid interfaces to prevent the demulsification [23]. Their adsorption on the fluid interfaces has been proved to be irreversible due to the huge desorption energy [24]. The steric hindrance with the formation of interparticle structures among the emulsion droplets is another proposed mechanism to illustrate the stability and the viscoelasticity of Mickering emulsions [25; 26; 27]. The present work studies the factors affecting the stability of Mickering emulsion to propose the mechanism of emulsification. The previous works to obtain smart microgels using surfactant free method are based on \(N\)-isopropyl acrylamide (NIPAm) polymers and its copolymers with acrylic (AA), methacrylic (MA), or 2-acrylamido-2-methyl propane sulfonic acids (AMPS) [28; 29; 30]. In this category of microgels, the low temperature and high pH conditions increased the swelling of particles and formed more stable Mickering emulsions. The shrinkage of NIPAm polymers at low pH and high temperature (above 35 \({}^{\circ}\)C) reduced the concentrations of soft gel interfaces due to the movement of microgel deeper into the oil phase and eventually alter the Mickering emulsions stability [31]. The destabilization of Mickering emulsions used the NIPAm microgels were dependent on the worse viscoelasticity and the dense crystalline array of the adsorbed microgel layer [31]. The electrostatic interactions among the charged microgel particles were ignored for the illustration of the stabilization mechanism when using charged NIPAm microgels [28]. The swelling and deformability of the charged NIPAM microgels were responsible for producing stable Mickering emulsion. In the present work, microgels based on poly acrylamides PAAm, PAMPS, and its sodium salt (PAMPS-Na) were prepared to investigate the effect of gel water content, surface charges, and particle sizes on the stability of Mickering emulsions. The polymerization of PAMPS, PAMPS-Na, and PAAm were carried out through the free-radical suspension polymerization. The work aims to illustrate the mechanism of stabilization of Mickering emulsions based on water/cyclohexane and microgels. These stable emulsions were applied for the production of smart crosslinked poly (styrene), PS, microspheres.