Surfactants are a special class of organic compounds whose amphiphilicity makes them tend to form a variety of aggregates. Surfactants can reduce the interfacial tension between the two phases. The characteristic parameters include critical micelle concentration (cmc), hydrophilic lipophilic balance (HLB), chemical structure, hydrophilic head charge and so on. The surface activity of surfactants makes them excellent emulsifiers, dispersants and foamers. As active ingredients in soaps and detergents, surfactants are often used for cleaning purposes to separate oily substances from specific substrates.
Numerous reviews and scientific reports describe the wide range of applications of surfactant micelles in pharmaceuticals, detergents, cosmetics, coatings, food science, nanotechnology, optoelectronics, bioremediation, oil recovery, chemical reactions, and drug delivery. Surfactants are widely used in industry as adhesives, flocculants, wetting agents, wetting agents, foaming agents, demulsifiers and penetrants because of their ability to reduce surface tension, increase solubility, decontamination, wetting, and so on. The petroleum industry has been in great demand for surfactants, including for washing oil and tertiary oil recovery, breaking milk, etc. Gemini surfactant is a special surfactant molecule that is widely used in the preparation of high porosity materials, phase transfer catalysts, body care products, drug encapsulation/release, antifungals and antimicrobials. At present, with the growth of market demand and concern for environmental issues, as a substitute for chemical surfactants, a class of biodegradable surfactants derived from microorganisms, known as biosurfactants, has emerged. Biosurfactants have attracted extensive attention in the fields of medicine and industry because of their excellent physicochemical properties, harmlessness, biocompatibility and chemical diversity.
The application field of surfactants is expanding day by day, and the chemical process is developing under the condition of green chemistry. At present, under the concept of green chemistry, researchers conduct catalytic reactions while trying to avoid waste of by-products, avoid the use of dangerous solvents, and strive to reduce energy costs from the perspective of supply and recovery. Previously, the application of surfactants in chemical reactions was mainly focused on laboratory-scale aqueous phase catalytic reactions. At present, however, it is rapidly upgrading to medical and industrial aspects. Today, the use of surfactants in drug formulations is gradually increasing, because in drug production, surfactants are successfully used to solubilize drugs and provide sufficient stability. The interaction between surfactant molecules and drug molecules is very important for the stability and solubilization (to prevent drug degradation) of the entire transport process of the drug in the biological system.
The analysis of surfactant aggregates and their potential applications is a hot topic, and such research also deals with the role of ordered assemblies in many chemical transformation processes. The suitability of a surfactant in a reaction depends mainly on the properties of the aggregates formed. Amphiphilic aggregation structures have been widely used in nanocatalytic reactors for organic reactions. In addition, surfactants have been successfully used to synthesize metal nanoparticles and have a stabilizing effect on the nanoparticles. In most cases, monomer surfactants participate in reactions catalyzed by metal nanoparticles in the form of aggregates, where the metal nanoparticles are stabilized by amphiphiles, polymer micelles, or dendritic macromolecules.
