Emulsions are thermodynamically unstable mixtures of immiscible liquids in single (typically oil and water), stabilized by amphiphilic surfactants that reduce interfacial tension [1]. While external forces disperse tiny droplets (0.1 to 100 μm) and amphiphilic surfactants reduce interfacial tension and other natural attractions between molecules [2], the thermodynamic instability makes the emulsion system vulnerable. The universal application of emulsions in pharmaceuticals, food, and cosmetics is limited by their susceptibility to degradation pathways like coalescence, flocculation, and Ostwald ripening [3], which reduce shelf-life and functionality. Physical separation and chemical degradation, driven by factors like pH shifts, oxidation, light, or temperature fluctuations, remain persistent challenges [4]. Numerous physicochemical strategies have been explored to overcome these limitations; however, it also raises product temperature, damages sensitive bioactive components, and increases costs, limiting their utilization.

For instance, in high-pressure homogenization, forcing fluids through micro-scale valve at 100–2000 bar generates intense shear and friction, rapidly elevating temperatures even in short cycles [5]. Similarly, ultrasonication produces cavitation bubble implosions that create localized ‘hot spots’ exceeding 5000 K, which heat the bulk product [6]. In hot homogenization, typically used for solid lipid nanoparticles (SLNs), intentional heating 5–10 °C above the lipid's melting point (e.g. 70–85 °C) is applied to prevent premature crystallization [7]. These thermal effects accelerate degradation reactions such as oxidation and hydrolysis; for example, vitamin C degradation rates can double with every 10 °C increase above 30–40 °C, while many enzymes and proteins irreversibly denature above 40–60 °C, resulting in substantial loss of bioactivity [5,7]. Modifying emulsion structure is another advanced approach including nanoemulsions, high internal phase emulsions, pickering emulsions, multilayer emulsions, SLNs, and emulgels. Despite their potential, they face significant barrier to widespread adoption such as high energy demands, complex fabrication processes, unpredictable release kinetics that can hinder bioaccessibility, and bioactive expulsion [8]. Currently, researchers are focused on adjusting emulsions with beneficial features such as low-calorie content [9], improving digestibility [10], and phenolic bioavailability [8]. Nonetheless, achieving stability during the processing and storage of product quality remains a crucial challenge [11].

Recent research has focused on utilizing imine-based surfactants (ImS), a promising approach that involves the use of dynamic covalent chemistry, particularly imine-bonds (I-bonds), to create responsive systems. Imine compounds (Schiff bases) feature reversible CN bonds formed through a condensation reaction between a primary amines and carbonyl group (aldehyde or ketone). This dynamic bond is the foundation of their unique properties, most notably its pH-dependent reversibility: stable under neutral or basic conditions but readily hydrolyzing in acidic environments. This inherent mechanism imparts pH sensitivity, self-healing, customizable functionality, and cost-effectiveness [12], which has led to imine chemistry (ImC) gaining immense commercial popularity. This dynamic bonding provides superior stability, allowing the emulsion to self-heal under stress by breaking and reforming I-bonds. Furthermore, the acid-labile nature of the I-bond enables the controlled release of bioactives in response to environmental conditions such as pH or temperature, making them useful for targeted drug and nutrient delivery [13]. By reducing reliance on conventional synthetic emulsifiers like polyethylene glycol derivatives, Tween 20 and Zonyl, imines offer ‘cleaner-label’ alternatives with better shelf life and stability [12]. The chemical structure of ImS is highly tunable; by selecting different amine and carbonyl precursors, functionalities e.g., antioxidant, antimicrobial, and droplet-size-controlling properties can be incorporated, providing a multifunctional alternative for emulsion design [14]. This ability to customize emulsifier structures allows precise control over emulsion properties and responsiveness, making it a valuable tool in advanced emulsion formulation.

This review highlights recent progress on ImS in emulsion systems, with emphasis on in situ interfacial formation, pH-responsiveness, reversibility, and self-healing capacity. It also addresses the intrinsic challenges of emulsion stability and the constraints these systems face across diverse industrial sectors, while noting the lacks of comprehensive evaluations of imine production processes and functional characteristics. The study emphasizes the potential of ImC to improve emulsification, alter surfactant behavior, and design responsive W/O interfaces. By clarifying underlying reaction mechanisms, dynamic interfacial behavior, and structure-function relationships, it provides pathways towards adaptive emulsions capable of responding to environmental fluctuations and broadening practical applications.