1. The Chemistry of Consumer Products Topic 2
Surfactants
The Chemistry of Consumer Products
Topic 2

2. Amphophiles Greek roots Ampophilic - two parts
Amphi – ‘double’ ‘from both sides’
Filos – friend
Ampophilic - two parts
Polar group – contains O, S, P, or N
Non-polar group – contains C, H

3. Amphophiles Hydrophilic or hydrophile Hydrophobe or lipophile
Likes water
Hydrophobe or lipophile
Fears water or likes grease

4. Amphophiles Not at ease in any solvent
Migrate to surfaces or interfaces
Surface – boundary between a condensed and gas phase
Interface – boundary between two condensed phases

5. Surface – Active – Agent
Surfactant
Short for
Surface – Active – Agent
Properties
Lower surface tension
Wetting agent
Emulsifier
Foaming agent
others

6. Surfactant types
Anionic
Nonionic
Cationic
Amphoteric / zwitterionic

7. Anionic Surfactants
Dissociate in water to give an amphophilic anion and acation (generally Na+, or K+)
Sodium Dodecyl Sulfate

8. Anionic surfactants Most common type Examples:
Alkylbenzene sulfonates (detergents)
Fatty acid soaps
Laury sulfate (foaming agent)
Di-alkyl sulfo succinate (wetting agent)
Lignosulfanates (dispersants)

9. Nonionic Surfactants Do not dissociate in water
An alcohol ethoxylate and an alkylphenol ethoxylate. The poly(ethylene oxide) chain forms the water soluble surfactant "head".
alkyl polyglycosides – contain one or more sugar groups

10. Nonionic Surfactants Second largest classification
Most have a hydrophilic group comprise of a polyethylene glycol chain produced by the condensation of ethylene oxide
Sugar based head groups are also used – low toxicity

11. Cationic Surfactants
Dissociate in water to give an amphophilic cation and an anion – usually a halogen
Fatty amine salts were the first style of cationic surfactant
The development of alkyl pyridinium and quaternary ammonium salts provided excellent surfactants that could be used over a vast range of conditions

12. Cationic Surfactants Generally more expensive than anionics
Used to target negatively charged substrates

13. Amphoteric / zwitterionic Surfactants
A zwitterionic surfactant has both an anion and a cation in one molecule chemically joined together. Zwitterionic surfactants are also called amphoteric surfactants as they often comprise a base coupled to an acid.
Three zwitterionic surfactants: an ammonium carboxylate, an ammonium sulfate and an amine oxide

14. Hybrid Surfactants
combines a nonionic surfactant with an anionic head group.
improves the behavior of the surfactants in hard water.
increases the range of temperatures over which the nonionic surfactants are soluble.
Sodium laureth sulfate

15. Saponification
The saponification reaction is the hydrolysis of fatty esters. The saponification reaction typically refers to the reaction that is carried out by a strong base. Historically, this was done with potash (potassium hydroxide) rather than sodium hydroxide, although nowadays we can obtain sodium hydroxide from the hydrolysis of seawater.

16. Properties of Solutions
Adsorption
Surface tension reduction
Self assembly

17. Adsorption
Adsorption is the tendency for a surfactant molecule to collect at an interface. (Adsorption is very different to absorption - don't get them confused!)

18. Adsorption
Surfactant molecules tend to adsorb to the surface of oil droplets. The hydrophilic heads stick out into the water phase, while the hydrophobic tails happily stick into the oil phase.

19. Reduction in surface tension

20. Self Assembly
Self-assembly is the tendency for surfactant molecules to organize themselves into extended structures in water. This includes the formation of micelles, bilayers and liquid crystals. These structures are formed when the hydrophobic tails of the surfactants cluster together, forming small aggregates such as micelles, or large layer structures (bilayers) which are similar to a cell wall.

21. Self assembly Surfactants can aggregate to form micelles.
There is usually between a few dozen to a couple of hundred surfactant molecules in a micelle
Surfactants also aggregate to form extended structures in water, such as surfactant bilayer, or rods

22. Micelle Formation
Micelles will begin to form when the concentration of the surfactant exceeds a limit known as the critical micelle concentration.

23. Detergency