Surfactants have become a flexible and diverse class of fine chemical products due to their physical and chemical effects such as wetting or anti-sticking, emulsification or demulsification, foaming or defoaming, solubilization, dispersion, washing, anti-corrosion, etc. Currently, surfactants are most widely used as detergents in daily life, but they have been found potentially useful in many other fields.

Characteristics of Surfactant

Surfactants can increase the solubility of poorly soluble drugs in the dispersion medium, because surfactants can form micelles, and surfactants are amphiphilic, if the polarity of the drug is small and the polarity of the dispersion medium is large, the solubility of the drug in the dispersion medium will become smaller according to the principle of similar compatibility. At this time, if we add a surfactant, the surfactant can form an association, and the side with the larger polarity is in contact with the dispersion medium. The side with smaller polarity is inward and away from the dispersion medium. Because the polarity of the drug is small, it can be encapsulated by the surfactant, which can achieve the purpose of increasing the solubility of the drug. In this case the surfactant is called a solubilizer.

Wetting effect
The effect of promoting the spreading or penetration of liquid on a solid surface is called wetting. Surfactants can act as wetting agents. The wetting effect of surfactants is that they can reduce the interfacial tension and contact angle of the solid-liquid contact interface.

Foaming and foam stabilization
Foam is a gas-liquid dispersion system. When the foam is formed, the contact area between gas and liquid will increase rapidly. At this time, a certain type of surfactant such as alcohol or alcohol amide, can form an adsorption film at the contact interface between the two, and thus achieve the purpose of foaming and stabilizing foam. General surfactants have good foaming ability, but their foam stabilization ability is not necessarily good. Adding surfactants to some external suppositories is beneficial to the uniform distribution of the drug in the cavity.

Classification of Surfactant

Surfactants can be divided into four categories according to their structural characteristics, namely, amphoteric surfactants, anionic surfactants, cationic surfactants, and non-ionic surfactants. Among them, anionic surfactants have better washing and foaming effects, and are mostly used in cleaning products. Cationic surfactants have better bactericidal, antistatic and hair-softening effects, and are mostly used in conditioners. Amphoteric surfactants have a weak cleaning effect, but have better foam increasing, foam stabilization and thickening effects, and therefore are mostly used to assist anionic surfactants in cleaning products to enhance the cleaning effect of products and reduce irritation. Nonionic surfactants are good at emulsification and solubilization, and have low irritation. They are mostly used in creams, lotions and water products that need to be solubilized.

In addition to soaps and detergents, surfactants are used in lubricants, inks, anti-fog liquids, herbicides, adhesives, emulsifiers and fabric softeners. Even the human body produces surfactants called pulmonary surfactants. The lungs produce surfactants at the cellular level that aid the breathing process by helping keep the airways open.

Difference Between Dispersant and Surfactant

Dispersant is a kind of surfactant with two opposite properties of lipophilicity and hydrophilicity at the same time in the molecule. It can uniformly disperse the solid and liquid particles of inorganic and organic pigments that are difficult to dissolve in liquids, and at the same time, it can prevent the sedimentation and agglomeration of particles, and form an amphiphilic reagent required for stable suspensions.

Surfactant refers to a substance that can significantly reduce the surface tension of the target solution. It has a fixed hydrophilic and lipophilic group, and can be aligned on the surface of the solution. The molecular structure of surfactants is amphoteric: one end is a hydrophilic group, the other end is a hydrophobic group. The hydrophilic group is often a polar group, such as carboxylic acid, sulfonic acid, sulfuric acid, amino or amine group and its salts. Hydroxyl, amide group, and ether bond can also be used as polar hydrophilic groups. In contrast, hydrophobic groups are often non-polar hydrocarbon chains, such as hydrocarbon chains with more than 8 carbon atoms. Surfactants are divided into ionic surfactants (including cationic surfactants and anionic surfactants), nonionic surfactants, amphoteric surfactants, compound surfactants, other surfactants, etc.

Author's Bio: 

The importance of surfactants is self-evident as they are an indispensable part in the manufacturing of our daily products such as detergents and textile. Having observed the great potentials of surfactants and also having noticed the growing demand for them, Alfa Chemistry now provides a full range of affordable, high-quality and reproducible surfactants for scientists who are involved with surfactant research or for industry manufacturers who need a reliable source of surfactants.