Emulsions are dispersions of great importance in various applications, whose kinetic stability is achieved through different strategies. In this work, we evaluate the role of mechanical stability provided by structured films, formed by ionic surfactants and co-surfactants, on their stability. The investigation began by varying the composition of the oil phase using isopropyl palmitate (IPP) and hexadecane, followed by a study on the impact of hexadecanol as a co-surfactant on the thermodynamics, structure, and stability of oil-in-water (O/W) emulsions using cetyltrimethylammonium chloride (CTAC) as the surfactant. The central objective was to elucidate the mechanisms of interfacial ordering and the phase transitions responsible for emulsion stability, as well as the influence of modifying the aqueous phase viscosity through the addition of water-soluble polymers to prevent creaming. Samples were characterized by Differential Scanning Calorimetry (DSC), Pendant Drop Tensiometry, Small-Angle and Wide-Angle X-ray Scattering (SAXS/WAXS), and optical and confocal microscopy. The results revealed two interfacial film ordering mechanisms: one at sub-ambient temperatures, relating to the crystallization of rotator phases of hydrocarbon chains; and another at higher temperatures, linked to the phase transition from the organized Lβ liquid crystal phase to the disorganized Lα phase, which requires the presence of the co-surfactant. The addition of hexadecanol shifted the transition temperature to a controllable range of 27 to 44 °C, imparting thermal responsiveness to the system. SAXS/WAXS measurements confirmed the presence of lamellar phases and the beta-alpha transition. The optimized system, containing 0.2% CTAC and 2.0% hexadecanol, demonstrated stability and resistance in accelerated stability analysis, proving crucial for the formation of High Internal Phase Emulsions (HIPEs). It is concluded that controlling the formation of the Lβ phase is the determining factor for stability, while the incorporation of water-soluble polymers represents an effective additional strategy for controlling macroscopic separation (creaming). The data cannot be made available due to intellectual property protection issues. For more information, contact the responsible parties.