What kinds of surfactants are there? What are the main functions and uses of various surfactants in cosmetics?

Surfactant refers to a substance with fixed hydrophilic and lipophilic groups, which is oriented to the surface energy of the solution and can significantly reduce the surface tension.

2. Composition: The molecular structure is amphiphilic.

Non-polar hydrocarbon chain: a hydrocarbon chain containing more than 8 carbon atoms.

Polar group: carboxylic acid, sulfonic acid, sulfuric acid, amino group or amine group and its salt, or hydroxyl group, amide group, ether bond, etc.

3. Adsorption:

Positive adsorption in solution: increase wettability, emulsification and foaming.

Adsorption on solid surface: single-layer adsorption on nonpolar solid surface,

Multilayer adsorption will occur on the surface of polar solid.

[Edit this paragraph] Classification of surfactants

Surfactants can be classified in many ways.

According to the structure of hydrophobic groups, they can be divided into straight chain, branched chain, aromatic chain and fluorine-containing long chain.

According to hydrophilic groups, it can be divided into carboxylate, sulfate, quaternary ammonium salt, PEO derivative, lactone and so on.

Some researchers have classified them into ionic and nonionic types according to their ionic properties, and there are many classification methods according to their water solubility, chemical structure characteristics and raw material sources. However, many classification methods have their limitations, and it is difficult to properly locate surfactants without overlapping conceptual connotations.

According to the dissociation properties of polar groups

1, anionic surfactant: stearic acid, sodium dodecyl benzene sulfonate.

2. Cationic surfactant: quaternary ammonium compound

3. zwitterionic surfactants: lecithin, amino acid and betaine.

4. Nonionic surfactants: fatty glycerides, fatty acid sorbitan (Span) and polysorbate (Tween).

Anionic surfactant

1, soap

It is a salt of higher fatty acids, and the general formula is: (rcooo ˉ) n m. Fatty acid hydrocarbon R is generally a long chain of 1 1~ 17 carbon, and the common ones are stearic acid, oleic acid and lauric acid. According to the different substances represented by m, it can be divided into alkali metal soap, alkaline earth metal soap and organic amine soap. They all have good emulsifying properties and the ability to disperse oil. But it is easily destroyed. Alkaline soap can also be destroyed by calcium and magnesium salts, and electrolyte can also make it salting out.

Alkaline soap: O/W

Alkaline earth metal soap: W/O

Organic amine soap: triethanolamine soap

2. Sulfate RO-SO3-M

Mainly sulphated oil and higher fatty alcohol sulfate. The aliphatic hydrocarbon chain r is between 12 and 18 carbons.

The representative of sulphated oil is sulphated castor oil, commonly known as Turkish red oil.

Higher fatty alcohol sulfates include sodium dodecyl sulfate (SDS, sodium lauryl sulfate)

Strong emulsification, stability, acid resistance, calcium resistance and magnesium salt resistance. Pharmaceutically, it can precipitate with some polymer cationic drugs, which has certain irritation to mucosa. It can be used as an emulsifier for external ointment, and can also be used for wetting or dissolving solid preparations such as tablets.

3. Sulfonated R-SO3-M

There are aliphatic sulfonates, alkyl aryl sulfonates and alkyl naphthalene sulfonates. Their water solubility, acid resistance, calcium resistance and magnesium salt resistance are slightly worse than sulfate, but they are not easy to hydrolyze in acidic solution.

Commonly used varieties are: sodium dioctyl succinate (Aloso -OT), sodium dodecyl benzene sulfonate, sodium glycocholate.

cationic surfactant

The active part of this surfactant is cation, so it is called normal soap. The main part of its molecular structure is a pentavalent nitrogen atom, so it is also called quaternary ammonium compound. It is characterized by high water solubility, stability in acidic and alkaline solutions, good surface activity and sterilization.

Commonly used varieties are benzalkonium chloride (bromogeramine) and benzalkonium bromide (bromogeramine).

Amphoteric cosmetic

This kind of surfactant has both positive and negative charge groups in the molecular structure, and can show the properties of cationic or anionic surfactants in different pH media.

1, lecithin: it is the main auxiliary material for preparing emulsion for injection and lipid microparticle preparation.

2. Amino acid type and betaine type:

Amino acid type: R-NH+2-CH2 CH2 Chief Operating Officer-

Type of betaine: R-N+(CH3)2- Chief Operating Officer.

It has the properties of anionic surfactant in alkaline aqueous solution and has good foaming and decontamination effects; In acidic solution, it is a cationic surfactant with strong bactericidal ability.

non-ionic surface active agent

1. Fatty acid glyceride: glyceryl monostearate;

HLB is 3~4, which is mainly used as auxiliary emulsifier of W/O emulsion.

2. polyols

Sucrose ester: HLB(5~ 13)O/W emulsifier and dispersant.

Fatty acid sorbitan (span): w/o emulsifier

Tween: O/W emulsifier

3. polyoxyethylene type: Myrij (long chain fatty acid ester); Fatty alcohol ester

4. polyoxyethylene-polyoxypropylene polymer: poloxamer

Emulsifiers and intravenous emulsions resistant to autoclaving and cryogenic freezing.

[Edit this paragraph] Basic properties of surfactants

1. Critical micelle concentration (CMC): the lowest concentration at which surfactant molecules associate to form micelles. When its concentration is higher than CMC value, surfactants are arranged in spherical, rod-shaped, bundle-shaped, layered/plate-shaped structures.

2. Hydrophilic-lipophilic balance value (HLB): the comprehensive affinity of hydrophilic-lipophilic groups in surfactant molecules for oil or water. According to experience, the HLB value of surfactant is limited to 0-40, and that of nonionic surfactant is 0-20.

Mixed additivity: HLB=(HLBa Wa+HLBb /Wb)/(Wa+Wb)

Theoretical calculation: HLB=∑ (HLB value of hydrophilic group)+∑ (HLB of lipophilic group)-7.

Basic properties of surfactants

Step 3 dissolve

1) micelle solubilization: the solubility of water-insoluble and slightly soluble drugs in micelle solution increased significantly.

Felodipine -0.025% Tween-10 times

(Table) Hydrophilic groups-lipophilic groups,

Polar group-nonpolar group

Cmc, the amount of "table", micelle? , solubilizing amount? , the maximum solubilization concentration (MAC)

[Edit this paragraph] Application of surfactants

1. Solubilization: C >；; CMC ( HLB 13~ 18)

Solubilization system is a thermodynamic equilibrium system.

The lower the CMC, the greater the association number and the higher the solubilization amount (MAC).

Effect of temperature on solubilization: temperature affects the formation of micelles, the dissolution of solubilizers and the solubility of surfactants.

Kraft point: the solubility of ionic surfactants increases sharply with the increase of temperature. This temperature is called the Kraft point. The higher the Kraft point, the smaller the critical micelle concentration.

Cloud point: for polyoxyethylene nonionic surfactants, when the temperature rises to a certain extent, the solubility drops sharply and precipitates, and the solution becomes turbid. This phenomenon is called haze, and this temperature is called haze point. When the polyoxyethylene chain is the same, the longer the hydrocarbon chain is, the lower the cloud point is. When the hydrocarbon chains are the same, the longer the polyoxyethylene chain, the higher the cloud point.

2. Emulsification:

HLB: 3-8 W/O emulsifier: Tween; ; Monovalent soap

HLB: 8- 16 O/W emulsifier: span; ; Bivalent soap

3. Wetting: (HLB: 7-9)

4. Suspension auxiliary device:

5. Firing and defoaming

6. Disinfection and sterilization

7. Cleaning agent

[Edit this paragraph] Structure of surfactant

Traditionally, surfactant is a substance that can significantly reduce surface tension even at very low concentration. With the in-depth study of surfactants, it is generally believed that all substances that can significantly change the surface (boundary) properties or properties related to and derived from them at low concentrations can be classified as surfactants.

No matter what kind of surfactant, its molecular structure is composed of two parts. One end of the molecule is a hydrophobic group, which is not extremely lipophilic, sometimes called lipophilicity; The other end of the molecule is a polar hydrophilic hydrophilic group, sometimes called oleophobic or figuratively called hydrophilic head. Two kinds of molecular fragments or groups with opposite structures and properties are located at the two ends of the same molecule, which are connected by chemical bonds to form an asymmetric polar structure, thus giving this kind of special molecules the characteristics of being hydrophilic and lipophilic but not hydrophilic and lipophilic as a whole. This unique structure of surfactant is usually called "amphipathic structure" (amphipathic).

Structure), surfactant molecules are often referred to as "amphiphilic molecules".

Depending on the required properties and specific applications, surfactants sometimes need to have different hydrophilic and lipophilic structures and relative densities. By changing the types, shares and positions of hydrophilic groups or lipophilic groups in the molecular structure, the required hydrophilic-lipophilic balance can be achieved. After years of research and production, many kinds of surfactants have been derived, and each kind contains many varieties, which makes it difficult to identify and choose a specific variety. Therefore, thousands of surfactants must be scientifically classified, which is conducive to further research and production of new varieties and provides convenience for the screening and application of surfactants.

[Edit this paragraph] The historical development of surfactants

The formation of surfactant and synthetic detergent industry can be traced back to 1930s. Synthetic surfactants and detergents derived from petrochemical raw materials have broken the situation that soap dominates the world. After more than 60 years of development, from 65438 to 0995, the total output of detergents in the world reached 43 million tons, including 9 million tons of soap. According to experts' prediction, the world population will double from 2000 to 2050, and the total amount of detergents will increase from 50 million tons to1.200 million tons, with a net increase of 1.4 Pei, which is an encouraging figure.

The surfactant and synthetic detergent industry in China started in 1950s, but developed rapidly. 1995 The total amount of washing products has reached 365,438+ten thousand tons, ranking second in the world after the United States. Among them, the output of synthetic detergent increased from 400,000 tons in 1980 to 2.3 million tons in 1995, with a net increase of 4.7 times and an average annual growth rate exceeding 10%. According to the forecast of the authoritative department of China, the total amount of washing products will reach 3.6 million tons in 2000, including 655,000 tons of synthetic detergent. Among them, the surfactants with output exceeding 1 10,000 tons are linear alkylbenzene sulfonate (LAS), fatty alcohol polyoxyethylene ether sodium sulfate (AES), fatty alcohol polyoxyethylene ether ammonium sulfate (AESA), sodium dodecyl sulfate (K 12 or SDS) and nonylphenol polyoxyethylene ether (10) (TX Diethanoamide (650 1) glyceryl stearate, lignosulfonate, heavy alkylbenzene sulfonate, alkyl sulfonate (petroleum sulfonate), diffuser NNO, diffuser MF, alkyl polyether (PO-EO*** polymer), fatty alcohol polyoxyethylene (3) ether (AEO-3), etc.

Relationship between chemical structure and properties of surfactants

1. Relationship between affinity balance value and performance

H L B value: indicates the hydrophilicity and hydrophobicity of surfactant.

(Hydrophilic-lipophilic balance)

In order to show unique interfacial activity, surfactants must maintain a certain balance between hydrophobic groups and hydrophilic groups.

The HLB value of paraffin wax =0 (without hydrophilic groups) and that of polyethylene glycol =20 (completely hydrophilic).

For anionic surfactants, HLB value can be determined by emulsifying standard oil.

HLB value is15 ~1813 ~158 ~ 87 ~ 93.5 ~1.5 ~ 3.

Uses Solubilizer Detergent Oil/Water Emulsifier Wetting Agent Water/Oil Emulsifier Defoamer

HLB value can be used as a reference for selecting surfactants.

3. Types and properties of hydrophobic groups

Hydrophobic groups are divided into four types according to applications.

(1) aliphatic hydrocarbon:

(2) Aromatic hydrocarbons:

(3) Mixed hydrocarbons:

(4) with weak hydrophilic groups

(5) Others: perfluoroalkyl

Hydrophobicity: (5)>( 1)>(3)>(2)>(4)

3. The position and properties of hydrophilic groups

End: strong cleaning effect and poor wettability; Chinese: On the contrary.

4. Molecular weight and properties

HLB value, same hydrophilic group and hydrophobic group, small molecular weight, good wetting effect and poor detergency;

Large molecular weight, poor wetting effect and good detergency.

5. Cloud point

For nonionic surfactants, hydrophilicity depends on the number of ether bonds, and the combination of ether and water molecules is an exothermic reaction.

When the temperature is ↑, the water molecules gradually leave the ether building and become turbid. The temperature at the beginning of turbidity is called cloud point. At this time, the surfactant will lose its function. The higher the cloud point, the wider the temperature range.