Anionic Surfactant

Anionic surfactants are a class of surfactants that carry a negative charge at the head of their molecular structure. Their hydrophilic groups typically contain functional groups such as sulfonates (-SO₃^-), sulfates (-OSO₃^-), and carboxylates (-COO^-), while their hydrophobic groups are usually long alkyl chains. These characteristics enable anionic surfactants to dissociate into anions in water, thereby reducing the surface tension of liquids and exhibiting excellent wetting, penetration, emulsification, dispersion, and solubilization properties. Common anionic surfactants include carboxylates, sulfonates, phosphates, and fatty acid ester salts.

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Characteristics of Anionic Surfactants

Structural Features

Consists of hydrophilic group and hydrophobic group

The molecular structure of anionic surfactants typically consists of two parts: a hydrophilic group at one end and a hydrophobic group at the other. The hydrophilic group is usually a negatively charged anion, such as carboxylate, sulfonate, or sulfate ester, while the hydrophobic group is a hydrocarbon chain or another hydrophobic moiety. This structure enables anionic surfactants to form stable foams in water and reduce surface tension.

For example, sodium lauryl sulfate (SLS) and sodium methyl ester sulfonate (MES) are common anionic surfactants with the following molecular structures:

Sodium Lauryl Sulfate (SLS): R-OH-CO-C₃H₅O₃^-
Sodium Methyl Ester Sulfonate (MES): R-O-C₃H₅O₃^-

Here, R represents the hydrophobic hydrocarbon group, while COO^- denotes the hydrophilic anionic group.

Performance Parameters

Critical Micelle Concentration (CMC)

The critical micelle concentration (CMC) is an important parameter for evaluating the surface activity of surfactants. When the concentration of a surfactant reaches the CMC, the surface tension of the solution begins to decrease significantly, and micelle structures start to form. A lower CMC indicates stronger surface activity of the surfactant.

For example, studies have shown that certain anionic surfactants, such as alkyl polyglucosides (APG), have relatively low CMC values, meaning they can significantly reduce surface tension even at lower concentrations.

Surface Tension Reduction Ability

Anionic surfactants function by reducing the surface tension of water. The ability to lower surface tension is closely related to the molecular structure and concentration of the surfactant. Generally, the higher the surfactant concentration, the lower the surface tension.

For instance, studies indicate that different types of anionic surfactants exhibit significant differences in surface tension values at the same concentration. APG demonstrates the lowest surface tension, indicating its strong ability to reduce surface tension.

Solubility, Foaming Properties, Wettability, and Detergency

Solubility

Anionic surfactants generally exhibit good solubility, forming clear or translucent solutions in water. For example, Sodium Lauryl Sulfate (SLS) and Sodium Fatty Alcohol Polyoxyethylene Ether Sulfate (MES) have excellent water solubility, making them suitable for various applications.

Foaming Properties

Anionic surfactants can generate abundant and stable foam. For instance, SLS and MES can produce a large amount of foam under appropriate conditions, making them ideal for use in detergents, shampoos, and similar products.

Wettability

Anionic surfactants possess excellent wettability, effectively reducing the contact angle between liquids and solid surfaces, thereby enhancing wetting performance. For example, SLS and MES demonstrate outstanding wettability in textile dyeing and papermaking processes.

Detergency

Anionic surfactants exhibit strong detergency, effectively removing grease and dirt. SLS and MES are widely used in detergents due to their superior cleaning performance.

Main Types and Representative Compounds

Alkyl Sulfates (AS)

Representative Compound: Sodium Dodecyl Sulfate (SDS), also known as Sodium Lauryl Sulfate (SLS).
SDS is a common anionic surfactant with excellent degreasing and cleaning properties. It is widely used in detergents, cosmetics, and pharmaceutical formulations.

Alkyl Ether Sulfates (AES)

Representative Compound: Sodium Lauryl Ether Sulfate (SLES).
SLES is produced by the ethoxylation of lauryl alcohol. It has good foam stability and mildness, making it commonly used in detergents, emulsifiers, and cleaning agents.

Sulfonates

Representative Compound: Sodium Dodecylbenzene Sulfonate (SDBS).
SDBS is an anionic surfactant with excellent emulsification and foaming properties, widely applied in detergents, cosmetics, and industrial cleaning agents.

Carboxylates

Representative Compound: Sodium Lauroyl Glutamate.
This carboxylate-based surfactant is known for its mildness and good foaming properties, commonly used in cosmetics and skincare products.

Phosphate Esters

Representative Compounds: Mono- and diester phosphate surfactants.
These compounds are typically synthesized from fatty alcohols and phosphoric acid. They exhibit good solubility and emulsification properties, making them widely used in industrial cleaners, emulsifiers, and solubilizers.

Applications of Anionic Surfactants

Personal Care Products

Anionic surfactants are widely used in personal care products, including shampoos, body washes, facial cleansers, and toothpaste. They exhibit excellent foaming, emulsifying, and cleansing properties, effectively removing dirt while maintaining skin mildness. For example, Sodium Lauryl Sulfate (SLS) and Sodium Laureth Sulfate (AES) are commonly used anionic surfactants found in shampoos and body washes. Additionally, these surfactants are incorporated into baby care products to minimize skin irritation.

Household and Industrial Cleaning

Anionic surfactants are extensively utilized in household and industrial cleaning products. They reduce water’s surface tension, creating abundant foam and effectively removing dirt. For instance, AES is widely used in household and industrial detergents due to its excellent detergency and foam stability. Furthermore, anionic surfactants are employed in car wash solutions, glass cleaners, and disinfectant hand washes.

Textile and Leather Industry

In the textile and dyeing industries, anionic surfactants play a crucial role in pre-treatment and dyeing processes by enhancing dye penetration and adhesion. They serve as wetting agents, emulsifiers, and penetrants, improving fabric properties and color uniformity. Additionally, anionic surfactants are used in leather processing to enhance dyeing quality and processing efficiency.

Agrochemicals

Anionic surfactants are primarily used in agriculture for emulsification and wetting in pesticide formulations, improving dispersion and stability. For example, Sodium Alkylbenzene Sulfonate (LAS) is widely used as a pesticide emulsifier, enhancing pesticide effectiveness and utilization. Moreover, anionic surfactants contribute to concrete performance enhancement and serve as wetting and emulsifying agents in construction coatings.

Petroleum and Mining

In the petroleum industry, anionic surfactants are employed in drilling fluid formulations, enhanced oil recovery, and crude oil extraction. They reduce oil/water interfacial tension, increase capillary number, and ultimately improve oil recovery efficiency. Additionally, anionic surfactants function as emulsifiers in lubricants, enhancing their stability and performance.

Pharmaceuticals and Biotechnology

Anionic surfactants play a vital role in pharmaceuticals, particularly in drug formulations and protein separation. They improve drug solubility and stability, enhancing therapeutic efficacy and safety. For example, AES is used in pharmaceutical formulations due to its excellent biocompatibility and low toxicity.

Personal Care Products

Household and Industrial Cleaning

Textile and Leather Industry

Agrochemicals

Petroleum and Mining

Pharmaceuticals and Biotechnology

Customers Often Look For

Our company's best-selling anionic surfactant has received high praise from customers for its excellent performance and wide range of applications. It offers outstanding cleaning power, good foaming properties, and remains stable even at low temperatures. It is suitable for various fields, including detergents, cleaning agents, and personal care products. We are committed to providing high-quality products and timely technical support to help customers enhance their product performance. By choosing our anionic surfactant, you will experience reliable and efficient cleaning results.

Our Services Include

To meet the diverse needs of our clients regarding surfactants, we offer comprehensive services including Dispersant and Surfactant Characterization, as well as Custom Synthesis and Product Development.

Dispersant and Surfactant Characterization

Dispersant and surfactant compounds, additives, and materials are tested, analyzed, and characterized at Alfa Chemistry's dispersant analysis laboratory.

Custom Synthesis and Product Development

Alfa Chemistry is prepared to effectively accomplish any demanding custom synthesis project in our custom synthesis laboratory, from milligrams to kilograms, based on years of expertise working with surfactant companies.

Case Study

Case 1: Application of Emulsifiers in the Cosmetics Industry

A cosmetics R&D team procured Sodium Surfactin from Alfa Chemistry to develop a new moisturizing lotion. Sodium Surfactin has an extremely low critical micelle concentration (CMC) of just 0.0003 wt%, significantly lower than that of common emulsifiers. This means that only a small amount is needed to achieve efficient emulsification.

During experiments, the team found that adding a small amount of Sodium Surfactin could form a gel with a high oil content, and the lotion remained stable without phase separation even after prolonged storage under high-temperature conditions. As a result, the final lotion was not only lightweight with excellent moisturizing properties but also passed low-irritation tests, making it suitable for sensitive skin.

Case 2: Application in Biomedical Research

A biomedical research team purchased high-purity Sodium Dodecyl Sulfate (SDS) from Alfa Chemistry for protein denaturation experiments. They utilized SDS's strong detergency properties, using it as a key reagent in SDS-polyacrylamide gel electrophoresis (SDS-PAGE) to separate and analyze protein samples. Through this experiment, the team successfully analyzed the molecular weight differences of the target protein and further studied its expression changes within cells, providing important data for subsequent drug development.

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