Surface active agents, also known as surfactants, are amphipathic molecules that contain both hydrophilic and hydrophobic portions. They can interact with both polar and non-polar substances, increasing the solubility of insoluble substances. In water, surfactant molecules form spherical clusters called micelles with the non-polar ends on the inside and polar ends on the outside. Surfactants are classified as anionic, cationic, non-ionic, or amphoteric based on their charge, and can be used as detergents, emulsifiers, wetting agents, and other products.

1. Surface Active AgentsPresented by: Sharanjeet Kaur

2. BASIC TERMINOLOGYHydrophilic: A liquid/surface that has a high affinity to water. Hydrophobic: A liquid/surface that has very low affinity to water Lipophilic: A liquid/surface that has a high affinity to oil. Lipophobic: A liquid/surface that has a very low affinity to oil.

3. A molecule that contains a polar portion and a non polar portion is called surface active agent/ surfactant.A surfactant can interact with both polar and non polar molecules. A surfactant increases the solubility of the otherwise insoluble substances. In water, surfactant molecules tend to cluster into a spherical geometry non polar ends on the inside of the sphere polar ends on the outside .These clusters are called micellesSurface active agents?

4. Surfactants have amphipathic structure tail or hydrophobic group little affinity for bulk solvent. Usually hydrocarbon (alkyl/aryl) chain in aqueous solvents. Can be linear or branched. Head or hydrophilic group strong affinity for bulk solvent. Can be neutral or charged.

5. Structure of a surfactant

6. Surfactants reduce the surface tension of water by adsorbing at the liquid-gas interface.

7. Many surfactants can also assemble in the bulk solution into aggregates. Examples of such aggregates are vesicles and micelles.

8. Thermodynamics of the surfactant systems are of great importance, theoretically and practically.

9. Surfactants play an important role as cleaning, wetting, dispersing, emulsifying, foaming

10. and anti-foaming agents in many practical applications and productsProperties

11. Classification of Surfactants1. Anionic2. Cationic3. Non- Ionic4. Amphoteric or Zwitterionic

12. Based on permanent anions or pH-dependent anions . These are categorised as:1. Sulfates: Alkyl sulfates, Alkyl ether sulfates2. Sulfonates: Sulfonatefluorosurfactants, Alkyl benzene sulfonates3. Phosphates: Alkyl aryl ether phosphate, Alkyl ether phosphate4. Carboxylates: Alkyl carboxylates, Carboxylatefluorosurfactants(~ 60% of industrial surfactants)Anionic Surfactants

13. Based on pH-dependent primary, secondary or tertiary amines i.e. primary amines become positively charged at pH < 10, secondary amines become charged at pH < 4.Examples:Cetylpyridinium chloride (CPC)Polyethoxylated tallow amine (POEA)Benzalkonium chloride (BAC)Benzethonium chloride (BZT)5-Bromo-5-nitro-1,3-dioxaneDimethyldioctadecylammonium chlorideCationic Surfactants

14. Amphoteric surfactants are characterized by the fact that these surfactants can carry a positive charge on a cationic site and a negative charge on an anionic site. The use of amphoteric terminology is still restrictive: The charge of the molecule must change with pH, showing a zwitterionic form at an intermediate pHExamples: Amino acidsImino acidsBetaines lecithinAmphoteric or Zwitterionic

15. Theydoesntincludeanychargedhead. These are categorised as: 1. FattyAlcohols2. Polyoxyethylene glycol3. Polyoxypropylenegylcol4. Glucoside5. Polyoxyethylene glycol octylphenol ethers6. Sorbitan alkyl esters7. Polyoxyethylene glycol sorbitan alkyl esters Non Ionic

16. The hydrophilic-lipophilic balance (HLB) of a surfactant reflects its partitioning behavior between a polar and non-polar medium. HLB number, ranging from 0-40, can be assigned to a surfactant, based on emulsification data. Semi-empirical only. Whatis HLB Scale?

17. Cont.. No dispersibility in water 0 antifoaming agents 2Water –in- oil emulsifier 6Wetting agent 8 Milky dispersion 10Oil-in-water emulsifier 12Clear solution 14Detergent 16Solubilizer 18A value of 10 represents a “mid-point” of HLB.

18. For non ionic surfactantsHLB = E/5 HLB = 20(1-S/A)Where ;E= percentage by weight of ethyleneoxideS= saponification number of esterA= Acidnumber of the fattyacidCalculation of HLB ‘s

19. Micelles are lipid molecules that arrange themselves in a spherical form in aqueous solutions. The formation of a micelle is a response to the amphipathic nature of fatty acids, meaning that they contain both hydrophilic regions (polar head groups) as well as hydrophobic regions. Micelles contain polar head groups that usually form the outside as the surface of micelles. They face to the water because they are polar. The hydrophobic tails are inside and away from the water since they are nonpolar.Micelles Formation

20. Cont.. Micelles contain polar head groups that usually form the outside as the surface of micelles. They face to the water because they are polar. The hydrophobic tails are inside and away from the water since they are nonpolar.Micelles form spontaneously in water, as stated above this spontaneous arrangement is due to the amphipatic nature of the molecule. when the lipids form micelles the hydrophobic tails interact with each other, and this interaction releases water form the hydrophobic tail and this increases the disorder of the system, and this is increase in entropy is favorable.