山东大学：《物理化学》课程教学资源（讲义资料）8.5 Surfactants, their properties and Applications（active learning）

88.5 Surfactants, their properties and Applications (active learning)

§8.5 Surfactants, their properties and Applications （active learning）

88.5 Surfactants and their properties and Applications 8.5.1 Surfactants The surface tension declines steeply Definition: The substances that even at c<×10-3 mol dm3 drastically lower the surface tension of water even at low concentrations. 1)Structure of surfactants The Amphiphilicity is the basic characters of surfactants: They have both polar and nonpolar moieties Hydrophilic group, hydrophobic/lipophilic group

Definition: The substances that drastically lower the surface tension of water even at low concentrations. 8.5.1 Surfactants The Amphiphilicity is the basic characters of surfactants: They have both polar and nonpolar moieties: Hydrophilic group, hydrophobic/lipophilic group. The surface tension declines steeply even at c < 10-3 mol dm-3 . 1) Structure of surfactants c  §8.5 Surfactants and their properties and Applications

88.5 Surfactants and their properties and Applications 8.5.1 Surfactants (1)Classification by structure/active moiety hydrophilic group CooH carboxyl anon I-OSO3H, sulphate IonIc cationic SO3 H, sulphonic acid NR4, ammonium amphoteric -CH2-CH2-O, poly-ethylene oxide etc. ester ether I hydrophobic group nonionIc I(CH2) (CF2) amide I(SiR2-O-) 4(CH2-CH2-CH2-0-)n nonionic-cationic nonionIc-anionIc branched linear or aromatic

8.5.1 Surfactants (1) Classification by structure/active moiety branched, linear, or aromatic §8.5 Surfactants and their properties and Applications

88.5 Surfactants and their properties and Applications 8.5.1 Surfactants (4)Classification on composition (2)Classification on functions Siloxane surfactants fluorosurfactants Emulsifier; deemulsifier, wetting agent, Organometallic surfactant: Zn soap, Mg soap anti-wetting agent, dispersant, vesicant, SO,H O F FFFF FFF (3)Classification on molecular weight (5) Classification on solubility M>10000, polymeric surfactant water-soluble surfactant oil-soluble surfactant OH ignIn

(2) Classification on functions Emulsifier; deemulsifier, wetting agent, anti-wetting agent, dispersant, vesicant, (3) Classification on molecular weight M > 10000, polymeric surfactant. (4) Classification on composition Siloxane surfactants, Fluorosurfactants Organometallic surfactant: Zn soap, Mg soap water-soluble surfactant oil-soluble surfactant (5) Classification on solubility 8.5.1 Surfactants §8.5 Surfactants and their properties and Applications

88.5 Surfactants and their properties and Applications 8.5.2 Critical micelle concentration and micelle When concentration(c) below ca. 10-3 mol-dm23 most ionic surfactants in aqueous solution display similar conductance as other strong electrolytes detergence Concentration-dependence of some physical properties of sodium dodecyl Surface tension sulfate between 1-2 x 10-3 mol-dm-3 Molar conductivity sharp breaks occur interface tension 0.2 0

8.5.2 Critical micelle concentration and micelle When concentration (c) below ca. 10-3 moldm-3 , most ionic surfactants in aqueous solution display similar conductance as other strong electrolytes. Concentration-dependence of some physical properties of sodium dodecyl sulfate: between 1~2  10-3 moldm-3 , sharp breaks occur. NaCl C12 C14 c  0 0.2 0.4 0.6 detergence Osmotic pressure Surface tension Molar conductivity interface tension §8.5 Surfactants and their properties and Applications

88.5 Surfactants and their properties and Applications 8.5.2 Critical micelle concentration and micelle A result presented by a student research group 0.046 0.044 0.042 z0.040 0.038 0000 0.036 0.034 6.0X10470x1048.0x1049.0x1041.0x1031.1x103 c/ mol dm

6.0x10-4 7.0x10-4 8.0x10-4 9.0x10-4 1.0x10-3 1.1x10-3 0.034 0.036 0.038 0.040 0.042 0.044 0.046  / N m c / mol dm-3 A result presented by a student research group 8.5.2 Critical micelle concentration and micelle §8.5 Surfactants and their properties and Applications

88.5 Surfactants and their properties and Applications 8.5.2 Critical micelle concentration and micelle In 1925. Mcbain postulated that at high concentration surfactant molecules aggregate to form micelle Small micell Ball-like micelle Layered micelle Rod-like micelle Micelles are usually charged S=, An equilibrium exists between micelle and individual surfactant

In 1925, Mcbain postulated that at high concentration, surfactant molecules aggregate to form micelle. Small micelle Ball-like micelle Layered micelle Rod-like micelle An equilibrium exists between micelle and individual surfactant Micelles are usually charged. 8.5.2 Critical micelle concentration and micelle S Sn n §8.5 Surfactants and their properties and Applications

88.5 Surfactants and their properties and Applications 8.5.2 Critical micelle concentration and micelle Detergents and cleaners Paints, lacquers and Cosmetics and persor Single molecules Surface adsorption Foods and packagin Insoluble surface layer Paper and ccllulose and pest control Small micelle lastics and composite Metal processing 崇 米 Medicine and biochemical Micelles Textiles and fibers (insoluble liquid)emulsion Oilfield chemicals Leather and furs (bubble)foam (Solid)dispersion/adsorption Mining and flotation Other "hi-tech"areas Chemical and other industnal applications

8.5.2 Critical micelle concentration and micelle §8.5 Surfactants and their properties and Applications Single molecules Surface adsorption Insoluble surface layer Small micelle Micelle (insoluble liquid)—emulsion (bubble)—foam (solid)—dispersion/adsorption

88.5 Surfactants and their properties and Applications 8.5.2 Critical micelle concentration and micelle b vesicle

vesicle 8.5.2 Critical micelle concentration and micelle §8.5 Surfactants and their properties and Applications

88.5 Surfactants and their properties and Applications 8.5.2 Critical micelle concentration and micelle CMC: detergence critical micelle concentration Osmotic The lowest concentration at which surfactant pressure molecules aggregate to form micelles Surface tension Molar conductivity -interface tension 0.2 0.4 0.6 Variation of the surface tension of the solution with the sodium decanoate concentration in 0.2 mol dm 3 Na so, at 40 Done in our research group c(mmol dm)

0 0.2 0.4 0.6 detergence Osmotic pressure Surface tension Molar conductivity interface tension CMC: critical micelle concentration The lowest concentration at which surfactant molecules aggregate to form micelles. Variation of the surface tension of the solution with the sodium decanoate concentration in 0.2 mol dm-3 Na2SO4 at 40 oC. Done in our research group. 8.5.2 Critical micelle concentration and micelle §8.5 Surfactants and their properties and Applications