2. INTRODUCTION
Surfactants, are wetting agent that lowers the surface tension of a liquid, allowing easier spreading,
dispersion and also lower the interfacial tension between the two liquids.
Surfactant are usually organic compounds that are amphipathic, as they contains both hydrophobic groups
(“tails”) and hydrophilic group (“head”). Therefore, they are soluble in both organic solvents and water.
Surfactant are indicated by the presence of both polar and non-polar region.
A surfactant molecule is composed of a hydrophilic head and a hydrophobic tail.
Similarly, the head can be an anionic, a cationic, a zwitterion, or a non-ionic group while the tail is a non-
polar hydrocarbon chain.
2
3. CLASSIFICATION OF SURFACTANT
According to the nature of the hydrophilic group surfactants are mainly classified as:
Anionic
Cationic
Non-ionic
Ampholytic
3
4. ANIONIC SURFACTANT
Those surfactant in which surface active ion is negatively charged in solution, are known as anionic
surfactant.
Anionic groups may be directly connected to hydrophobic part of these may be connected through
ester, amide and amidine links.
Eg: Sodium Dodecyl Sulphate.
4
5. Surfactant having anionic groups connected directly to the hydrophobic unit.
Ex: Fatty acid soaps, alkyl sulphonates, alkyl sulphates, alkyl aryl sulphonates and alkyl phosphates.
Surfactant having anionic groups connected through ester links.
Ex: Monoglyceride sulphates, dialkyl sulphosuccinate, polyethylene glycol ester and sulphate isoethionates.
Surfactant having anionic groups connected through ether links.
Ex: Alkyl ether sulphate, phenol ether sulphates and alkyl ether carboxylates.
Surfactant having anionic groups connected through amide links.
Ex: Alkalonamide sulphates, taurined and sarcosinates.
Surfactant having anionic groups connected through amidine links.
Ex: Imidazole sulphate
5
6. CATIONIC SURFACTANT
Those surfactant in which surface active ion is positively charged in solution, are known as cationic
surfactant.
6
7. NITROGENOUS SURFACTANT
Quaternary ammonium salts in which nitrogen is directly attached to the hydrophobic part. Eg. Alkyl
trimethyl ammonium salts, dialkyl dimethyl ammonium salts, alkyl dimethyl benzyl ammonium salts,
ethoxylated alkyl-dimethyl ammonium salts.
Surfactants in which the cationic group separated from the hydrophobic group. Eg. Quarternized
amides of ethylene diamine, quartemized amides of polyethyleneamine.
Surfactant in which cationic group is located in a heterocyclic ring. Eg. Alkyl pyridium salts, alkyl
mophoinium salts and alkyl imidaxolinium salts.
Dicationic surfactant: eg. Quarternized diamine salts.
Non-Nitrogenous Surfactant: Eg. Sulphonium salts, phosphonium salts.
7
8. NON-IONIC SURFACTANT
Hydrophilic part of the molecule is made up of multiple uncharged polar groups. Eg. Hydroxyl group
or ether linkage in ethylene oxide chains.
8
10. AMPHOTERIC (ZWITTER-IONIC) SURFACTANT
Its able to form a surface active ion with both positive and negative charge.
Three types:
01. Alkyl B aminopropionates, betaines.
02. Acylaminoacids: Acyl B amino propionates, acyl peptides.
03. Alkylimidazolines.
10
11. APPLICATION OF SURFACTANTS
“EMULSIFICATION PURPOSE”
Anionics
Widely used for emulsifying
purposes especially in the
formulations of hand creams
and lotions.
Ex. Fatty acids soaps, fatty
acid monoesters containing
fatty acid soaps, Sulphuric
esters etc.
Cationic
Not widely used as emulsifying agents
in cosmetics.
Following properties:
• Substantive to proteins at acid pH.
• Produce emulsions with acid pH.
• They germicidal properties if not
inactivated by anionic or
incompatible materials.
Non-ionic surfactants
Compatible with large number of
cosmetics because they do not
ionize in solution. They are
compatible with both anionic and
cationic surfactants.
Ex; polyoxyethylene fatty acids
esters, polyoxyehtylene fatty
alcohol ethers, sorbitan fatty acid
ester (sorbitol monosterate).
Manu cosmetics are emulsions in which surfactants have been used as the emulsifying agents. They are three types
usually used as emulsifying agents: anionic, cationic and non-ionic.
11
12. FOAMING AND CLEANSING PURPOSE
Anionic surfactants
Most widely used for laundering,
dishwashing liquids and shampoos
because of its excellent cleaning
properties.
In the shampoo the anions such as
alkaline sulphonates and alkaline
benzene sulphonates and fatty
acids soaps are not used.
Sulphosuccinates are known for
the mild effects and less irritant to
eyes and used in mild shampoo as
auxiliary surfactants.
Methyl taurides and acyl peptides
may be used.
Cationic surfactants
They are not goof foaming
agents or detergent.
Also irritant to eyes and interact
with proteins, thus they causes
dirt re-disposition on hair shaft.
They can be used as additives
for germicidal in 5% shampoo.
Ex. Alkyl trimethyl ammoniums
and cetyl pyridinium salts.
Non-Ionic Surfactant
Good detergent and used as
principle surfactants.
Polyglyceryl ethers have good
detergency and foaming
properties.
Non-ionic used for increasing
the stability and viscosity.
Alkanolaminde as non-ionic
surfactant but not used as
detergents but produce
conditioning effects.
Ex. Pluronics and sorbitol
esters
For this purpose, surfactants are used mostly in shampoo, in which the principle ingredients are surfactants. For
foaming and cleansing anionics, cationic, non-ionic and amphoteric surfactant are used.
12
13. AMPHOTERIC
SURFACTANTS
Mainly used in mild shampoo
such as baby shampoo because
of their mildness to skin and
eye.
They are known to have
conditioning properties.
E.g.: n-Alkyl amino acids
and betaines and
imidazoline derivatives.
They are stable over a wide
range of pH (2-12). They are
also compatible with cationic,
anionics and non-ionics.
Surface-active compounds with both acidic and alkaline properties are known as
amphoteric surfactants. Amphoteric surfactants include two main groups, i.e.
betaines and real amphoteric surfactants based on fatty alkyl imidazolines.
13
14. APPLICATIONS
Wetting Agents
All surfactants have good wetting properties.
For the purpose of enhancing the wetting, the
short chain alkyl aryl sulphonates, alkyl ethyl
sulphates are often used for improving wetting
properties.
Solubilization
Surfactant when used above CMC are known to
have solubilizing properties.
For incorporating perfumes in cosmetics or
certain additives which requires solubilization.
14
15. COMMONLY USED SURFACTANTS
Sodium lauryl sulphates (can be derived from coconuts) produces high foam; easy to thicken. Strong
anionic surfactant; can cause irritation.
Decyl glucoside (derived from sugar) anionic surfactant; gentle on the skin.
Glyceryl cocoate (derived from vegetable).
Disodium lauryl sulphosuccinate (derived from coconuts), foaming agent.
Mild decyl polyglucoside ( vegetable derived, used in baby shampoo for its gentleness.
Cetearyl alcohol (derived from coconut oil) amphoteric surfactant.
15
16. HYDROPHILIC–LIPOPHILIC BALANCE (HLB) SCALE
Hydrophilic–lipophilic balance (HLB) is the balance of the size and strength of the hydrophilic and
lipophilic moieties of a surfactant molecule.
The HLB scale ranges from 0 to 20.
In the range of 3.5 to 6.0, surfactants are more suitable for use in W/O emulsions.
Surfactants with HLB values in the 8 to 18 range are most commonly used in O/W emulsions (Griffin,
1949).
16
18. REFERENCES
Griffin, W. C. (1949). Classification of surface-active agents by" HLB". J. Soc. Cosmet. Chem., 1, 311-
325.
Schwartz, A. M., Perry, J. W., & Bartell, F. E. (1949). Surface Active Agents. The Journal of Physical
Chemistry, 53(9), 1467-1467.
Schwarz, E. G., & Reid, W. G. (1964). Surface-active agents—Their behavior and industrial use.
Industrial & Engineering Chemistry, 56(9), 26-31.
Glassman, H. N. (1948). Surface active agents and their application in bacteriology. Bacteriological
reviews, 12(2), 105-148.
18
