1. SURFACTANTS IN SOLUTION

2. Amphiphilic Surfactants Amphiphilic surfactants contain a non-polar portion and a polar portion. Aerosol OT

3. Classification of Surfactants  Anionic  Cationic  Zwitterionic  Nonionic Sodium dodecylsulfate (SDS) Cetylpyridinium bromide Dipalmitoylphosphatidylcholine (lecithin) Polyoxyethylene(4) lauryl ether (Brij 30)

4. 4 nm Unimers Normal micelles spherical cylindrical Bilayer lamella Reverse micelles Inverted hexagonal phase Surfactant Aggregates

5. Molecular Architecture Aerosol OTSodium dodecylsulfate (SDS)

6. 0 2 4 6 8 10 12 14 01 Surfactant concentration CMC  Critical Micelle Concentration CMC Below CMC only unimers are present Above CMC there are micelles in equilibrium with unimers

7. Solution Properties 0 2 4 6 8 10 12 14 01 Surfactant concentration CMC Concentration unimers micelles 0 2 4 6 8 10 12 14 01 Surfactant concentration CMC Osmotic pressure  0 2 4 6 8 10 12 14 01 (Surfactant concentration) 1/2 CMC Molar conductivity 1/R 0 2 4 6 8 10 12 14 01 Surfactant concentration CMC I sc Light scattering

8. Solubilization Spontaneous transfer of a compound insoluble in the bulk solvent into solution due to incorporation into the surfactant micelles polar compound Reverse micelles non-polar compound Normal micelles amphiphilic compound

9. Solubility Effects Solubility of a poorly soluble compound increases as a result of solubilization in the micelles 0 2 4 6 8 10 12 14 01 Surfactant concentration CMC Solubility

10. HLB and Use of Surfactants 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 Amphiphilic surfactants are characterized by the hydrophilic-lipophilic balance (HLB): a relative ratio of polar and non-polar groups in the surfactant

11. Required HLB 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. Required HLB Fraction (from reference) Cetyl alcohol15x15/1812.5 White wax12x1/180.7 Lanolin10x2/181.1 Total required HLB14.3 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.

12. HLB of Surfactant Blend What is the HLB of the mixture of 40 % Span 60 (HLB = 4.7) and 60 % Tween 60 (HLB = 14.9)? 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 = 12x = 0.72 72 % Tween 80 and 28 % Span 80 Surfactant blends are commonly used to obtain desired emulsifying properties.