Surfactant Aggregation

1 Nature of Surfactants.- 1.1 Introduction to surfactants.- 1.2 Natural surfactants.- 1.3 Synthetic surfactants.- 1.4 Types of surfactant.- 1.4.1 Hydrophilic groups.- 1.4.2 Hydrophobic groups.- 1.5 Surface activity.- 1.5.1 Self-association.- 1.5.2 The hydrophobic effect.- References.- 2 Adsorption at liquid interfaces.- 2.1 Introduction.- 2.2 Direct measurement of amount adsorbed.- 2.3 Adsorption studied via surface and interfacial tension measurement.- 2.4 Adsorption of ionic surfactants.- 2.4.1 No added electrolyte.- 2.4.2 Ionic surfactant with excess electrolyte.- 2.5 Equations of state for adsorbed surfactants.- 2.6 Adsorption at the liquid/liquid interface.- 2.7 Ultra-low interfacial tensions.- 2.7.1 Prediction of emulsion type from packing geometry.- 2.7.2 Phase inversion.- 2.7.3 Tensions at curved and planar interfaces.- 2.7.4 Interactions between adsorbed monolayers.- 2.7.5 Practical applications of ultra-low tension systems.- 2.8 Physical properties of adsorbed monolayers.- 2.9 Dynamic aspects of adsorbed surfactants.- 2.9.1 The Marangoni effect.- References.- 3 Insoluble monolayers.- 3.1 Introduction.- 3.2 Historical background.- 3.2.1 The Langmuir trough and its origin.- 3.2.2 Use of the Langmuir trough.- 3.3 Phase changes and types of film.- 3.3.1 Gaseous films.- 3.3.2 The LE + G region.- 3.3.3 The liquid-expanded region.- 3.3.4 The transition region.- 3.3.5 The liquid-condensed region.- 3.3.6 The solid region.- 3.4 Ionised monolayers.- 3.4.1 Effect of polyvalent counterions.- 3.5 X-ray and neutron scattering.- 3.5.1 Horizontal scattering.- 3.5.2 Vertical scattering.- 3.5.3 Neutron scattering.- 3.6 Dynamic effects.- 3.6.1 Interfacial shear rheology.- 3.6.2 Interfacial dilatational rheology.- 3.6.3 Measurement of surface shear viscosity for insoluble monolayers.- 3.6.4 Measurement of surface dilatational rheological properties.- 3.7 Practical applications of insoluble monolayers.- References.- 4 Langmuir—Blodgett multilayers.- 4.1 Introduction.- 4.2 Historical background.- 4.3 Types of monolayer deposition.- 4.3.1 X-, Y- and Z-films.- 4.3.2 Incomplete deposition.- 4.3.3 Asymmetrical films.- 4.3.4 Polymeric systems.- 4.4 Structure of multilayers.- 4.4.1 Characterisation by simple techniques.- 4.4.2 Low-angle X-ray diffraction.- 4.4.3 Spectroscopic methods.- 4.4.4 Long-range order and homogeneity.- 4.5 Applications of LB films.- 4.5.1 Devices exploiting the insulating properties of the film.- 4.5.2 Applications combining ultra-thin property with useful chemistry.- 4.5.3 Multilayers requiring non-centrosymmetrical structures.- 4.5.4 Supermolecular assemblies and molecular electronics.- 4.5.5 Sensors.- 4.6 Self-assembly systems.- 4.6.1 Self-assembly monolayers.- 4.6.2 Self-assembly multilayers.- References.- 5 Micelle formation.- 5.1 Evidence for micelle formation.- 5.2 Structure of micelles.- 5.2.1 Hartley’s model for spherical micelles.- 5.2.2 Simple geometric factors.- 5.2.3 Spherical micelles.- 5.2.4 Cylindrical micelles.- 5.2.5 Counterion binding.- 5.3 Dynamics of micellar aggregation.- 5.3.1 The multiple equilibrium model.- 5.4 The critical micelle concentration (CMC).- 5.4.1 Ionic surfactants.- 5.4.2 Non-ionic surfactants.- 5.4.3 Factors affecting the CMC.- 5.4.4 Methods for measuring the CMC.- 5.5 Thermodynamics of micelle formation.- 5.5.1 Simple thermodynamic theory.- 5.5.2 Experimental data for the thermodynamic parameters of micellisation.- 5.5.3 Mechanism of micelle formation.- 5.6 Solubilisation.- 5.6.1 Polar solubilisates.- 5.6.2 Effect of temperature and electrolyte addition.- 5.7 Applications of micellar solutions.- 5.7.1 Detergency.- 5.7.2 Application of cylindrical micelles.- 5.7.3 Solubilisation.- 5.7.4 Micellar-enhanced ultrafiltration.- 5.7.5 Micellar catalysis.- References.- 6 Mixed-micelle formation.- 6.1 Qualitative observations.- 6.2 Thermodynamics of mixed-micelle formation.- 6.2.1 Surface tensions of surfactant solutions.- 6.3 Thermodynamics of non-ideal mixed-micelle formation.- 6.3.1 Mixtures where one component does not form micelles.- 6.3.2 Non-ideality in the interface.- 6.4 Some major findings—surfactant synergisms.- 6.5 Further examples of mixed-micelle formation.- 6.6 Positive deviations from ideality—mixtures of perfluoro and hydrocarbon surfactants.- References.- 7 General phase behaviour of surfactants.- 7.1 General features of surfactant phase behaviour.- 7.2 The Krafft boundary.- 7.2.1 Design of surfactants for use in hard water.- 7.2.2 Products making use of Krafft boundary effects.- 7.2.3 Dependence of Krafft temperature on surfactant structure.- 7.3 The cloud point.- 7.3.1 Mechanism of phase separation.- 7.3.2 Nature of the separated phases.- 7.3.3 Practical importance of cloud point phenomena.- 7.4 Mesomorphic phases.- 7.4.1 Quantitative phase diagram ‘cuts’.- 7.4.2 Quantitative phase cuts—‘diffusive interfacial transport’.- 7.4.3 General disposition of mesomorphic phases.- 7.4.4 Hexagonal phases H1 and H2.- 7.4.5 Lamellar phase L?.- 7.4.6 Cubic phases.- 7.4.7 Fluctuations close to phase boundaries.- 7.4.8 Physical state of molecules in liquid-crystal phases.- 7.4.9 The surfactant molecules.- 7.4.10 The state of water molecules.- 7.4.11 Other lyotropic liquid-crystalline phases.- 7.4.12 Applications of surfactant phase information.- References.- 8 Dispersions of surfactant aggregates.- 8.1 Introduction.- 8.2 Vesicles and liposomes.- 8.2.1 Biological membranes.- 8.2.2 Synthetic membrane-forming surfactants.- 8.2.3 Preparation of liposomes and vesicles.- 8.2.4 Stability of vesicles and liposomes.- 8.2.5 Properties of liposomes.- 8.3 Applications of liposomes.- 8.3.1 Drug carriers.- 8.3.2 Reaction microenvironments.- 8.3.3 Freeze-dried liposomes.- 8.3.4 Fabric and hair conditioners.- 8.3.5 Stability of liposome dispersions.- 8.4 Dispersions of crystals.- 8.4.1 Surfactant gels.- 8.4.2 Use in detergent products.- 8.4.3 Hard-surface cleaners.- References.- 9 Adsorption on solids.- 9.1 Introduction.- 9.1.1 Experimental determination of amount adsorbed.- 9.1.2 Adsorption isotherms.- 9.1.3 Thermodynamics of adsorption onto solids.- 9.2 Adsorption at very low concentration.- 9.3 Lateral interactions between adsorbed surfactant molecules.- 9.3.1 Nature of the adsorbed layer.- 9.3.2 Adsorption at higher concentrations.- 9.4 Effect of surfactant structure on adsorption.- 9.4.1 Non-ionic surfactants on hydrophobic surfaces.- 9.4.2 Non-ionic surfactants on hydrophilic surfaces.- 9.4.3 Zwitterionic surfactants on hydrophilic surfaces.- 9.4.4 Ionic surfactants on hydrophobic surfaces.- 9.4.5 Ionic surfactants on hydrophilic surfaces.- 9.5 Stabilisation of dispersions.- 9.5.1 Forces between particles.- 9.5.2 Combined dispersion and electrostatic forces.- 9.5.3 Combined dispersion and steric forces.- 9.6 Other applications.- 9.6.1 Froth flotation.- 9.6.2 Detergency.- 9.6.3 Corrosion inhibition.- 9.6.4 Water purification.- 9.6.5 Admicellar chromatography.- 9.6.6 Enhanced oil recovery.- References.- 10 Microemulsions.- 10.1 Definition of microemulsions.- 10.2 Use of co-surfactants.- 10.3 Interfacial tension in microemulsions.- 10.4 Properties of microemulsions.- 10.4.1 Characterisation of microemulsions.- 10.4.2 Simple geometric considerations.- 10.4.3 Electron microscopic observations.- 10.4.4 Scattering techniques.- 10.4.5 Self-diffusion measurements.- 10.5 Applications of microemulsions.- 10.5.1 Microemulsions as products.- 10.5.2 Microemulsions as physical process aids.- 10.5.3 Microemulsions as chemical reaction media.- 10.5.4 Surfactant-enhanced oil recovery.- References.- 11 Surfactant bilayers, foams and emulsions.- 11.1 Introduction.- 11.2 Soap films.- 11.2.1 Film drainage.- 11.2.2 Factors affecting drainage rate.- 11.2.3 Structure of drained films.- 11.3 Measurement of film thickness.- 11.3.1 Factors affecting film thickness.- 11.3.2 Thin-film tensions.- 11.3.3 Film stability.- 11.4 Foams and foam stability.- 11.4.1 Bulk viscosity.- 11.4.2 Surface viscosity.- 11.4.3 Antifoams.- 11.4.4 Non-aqueous foams.- 11.5 Lipid bilayers.- 11.5.1 Permeability of bilayer lipid membranes.- 11.6 Formation and stability of emulsions.- 11.6.1 Coalescence.- 11.6.2 Emulsion type.- 11.6.3 Mixed emulsifiers.- 11.6.4 High internal phase ratio (HIPR) emulsions.- 11.6.5 Demulsification.- References.