SURFACTANT
S IN
SOLUTION
Classification of
Surfactants
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•
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Anionic
Cationic
Zwitterionic
Nonionic
O
S - +
O Na
O
Sodium dodecylsulfate (SDS)
+
N
Br-
Cetylpyridinium bromide
O
O
O
OCH2CH2N(CH3)3+
P OO
O
Dipalmitoylphosphatidylcholine (lecithin)
O
O
O
Polyoxyethylene(4) lauryl ether (Brij 30)
O
OH
Surfactant Aggregates
Unimers
Normal micelles
cylindrical
spherical
Inverted hexagonal phase
Reverse micelles
Bilayer lamella
4 nm
Critical Micelle Concentration
CMC
14
12
10
8
6
CMC
4
2
0
0
1
Surfactant concentration
• Below CMC only
unimers are present
• Above CMC there are
micelles in equilibrium
with unimers
Solution Properties
14
12
10
8
6
4
2
0
14
 12
Concentration
unimers
10
8
6
4
2
0
CMC
micelles
0
Surfactant concentration1
14
Isc12
10
8
6
4
2
0
Osmotic pressure
CMC
0
Surfactant concentration1
Light scattering
CMC
0
Surfactant concentration1
Solubilization
• Spontaneous transfer of a compound insoluble in
the bulk solvent into solution due to incorporation
into the surfactant micelles
Normal micelles
non-polar compound
amphiphilic compound
Reverse micelles
polar compound
Solubility Effects
• Solubility of a poorly soluble compound increases
as a result of solubilization in the micelles
Solubility
14
12
10
8
6
CMC
4
2
0
0
1
Surfactant concentration
An example of an HLB value
calculation
• BRIJ ® 98 INCI name : oleth-20 is a 20 mole
ethoxylate of oleyl alcohol
• calculate the molecular weight of the 20
moles of ethylene oxide ( one mole ETO =44
);
20 x 44 = 880
• add this number to the molecular weight of
the oleyl alcohol;
880+ 270 = 1150 ( the mol. wt of BRIJ 98 )
• What percentage of 1150 is 880 ?
880/1150 = 76.5%
• 76.5% divided by 5 = 15.3
• 15.3 is the HLB value of BRIJ 98
Important to remember !
HLB and Use of Surfactants
Amphiphilic surfactants are characterized by the
hydrophilic-lipophilic balance (HLB): a relative
ratio of polar and non-polar groups in the surfactant
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HLB ca. 1 to 3.5: Antifoams
HLB ca. 3.5 to 8: Water-in-Oil Emulsifiers
HLB ca. 7 to 9: Wetting and spreading agents
HLB ca. 8 to 16: Oil-in-Water Emulsifiers
HLB ca. 13 to 16: Detergents
HLB ca. 15 to 40: Solubilizers
Required HLB
HLB needed for emulsification of the oil phase. If there
are several oil ingredients the required HLB is
calculated as a sum of their respective required HLB
multiplied by the fraction of each.
• Calculate the required HLB for the oil phase of the following o/w
emulsion: cetyl alcohol 15 g., white wax 1g. Lanolin 2 g,
emulsifier (q.s.), glycerin 5 g. water 100 g.
Cetyl alcohol
White wax
Lanolin
Total required HLB
Required HLB
(from reference)
15
x
12
x
10
x
Fraction
15/18
1/18
2/18
12.5
0.7
1.1
14.3
HLB of Surfactant Blend
Surfactant blends are commonly used to obtain
desired emulsifying properties.
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•
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Span 60 (HLB = 4.7)
Tween 60 (HLB = 14.9)
Span 80 (HLB = 4.3)
Tween 80 (HLB = 15.0)
What is the HLB of the mixture of 40 % Span 60 (HLB =
4.7) and 60 % Tween 60 (HLB = 14.9)?
Sorbitan monostearate is an ester of
sorbitol and stearic acid (synthetic wax)
Polyoxyethylenesorbitan monooleate;
Sorbitan monooleate ethoxylate
HLB of mixture: 4.7 x 0.4 + 14.9 x 0.6 = 10.8
In what proportion should Span 80 (HLB = 4.3) and Tween
80 (HLB = 15.0) be mixed to obtain “required” HLB of 12.0?
4.3.(1-x) + 15.x = 12 x = 0.72
72 % Tween 80 and 28 % Span 80
Glycerol Monostearate
HLB value of 3.6~4.2
dissolves in hot grease, paraffine, ethanol, chloroform, acetone
and aether, the material is widely used when producing of chocolate,
margarine, ice cream, skin care balsam, cold cream, hair oil and drug
ointment, also lubricant for plastic processing
Shampoo
Ingredients
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Isobutane
Cyclomethicone
Aluminum Chlorohydrate
Propylene Glycol Dicaprylate/Dicaprate
Lichen extract
Fragrance
Quaternium-18
Silica
Dimethiconol
cyclomethicone
Propylene Glycol Dicaprylate/Dicaprate
Facial Cleanser
Aqua/Water
Palmitic acid
Myristic acid
Lauric acid
Stearic acid
Potassium hydroxide
PEG-7 Glyceryl cocoate
PEG-150 Distearate
Glycerin
Sodium laureth sulfosuccinate
Limonene
Linalool
Zinc PCA
Propylparaben
Propylene glycol
Disodium EDTA
NaCl
Propylene glycol
propyl ester of p-hydroxybenzoic acid = propylparaben
zinc salt of 2-Pyrrolidone-5-Carboxylic Acid
PEG-7 Glyceryl cocoate
Polyoxyethylene glycol glyceryl cocoate (monococoate).
PEG-150 Distearate
Polyethylene glycol diester of stearic acid.
Sodium laureth sulfosuccinate
Cream