Emulsions, Microemulsions and Foams

1.    Common background (about 100 pages) 1.1    Interfaces between pure fluids

·       Surface tension, Contact angle, wetting

·       Interface thickness: intrinsic profile, thermal fluctuations

1.2. Irreversibly adsorbed surface-active species

·       Surface pressure, surface rheology (compression and shear, viscoelasticity)

·       Polymer layers: thickness, rheology, case of proteins

·       Other species: asphaltenes, particles

·       Mixed layers

 

1.3.  Surfactant layers

·       Adsorption-desorption: Gibbs description, validity of the Gibbs equation, Langmuir equation of state, energy barriers, depletion.

·       Non-equilibrium systems: sorption and transfer kinetics, "dynamic" tension

·       Surface rheology: extension of Gibbs description, resistance to compression and shear, viscoelasticity, Levich model, influence of the surface charge

 

1.4  Thin films: Interaction between surfaces (van der Waals, electrostatic, short range), disjoining pressure. Oscillatory forces, film stratification

 

1.5  Surfactants and self-associated systems: micelles, lyotropic liquid crystals,

·       Surfactant parameter, link with HLB, HLD and PIT

·       Critical micellar concentration, link with surfactant solubility, exchanges with bulk

·       Micelle size distribution, micelles in organic solvents

·       Lyotropic liquid crystalline phases, phase diagrams, dispersed phases (cubosomes, hexosomes)

 

2.  Microemulsions (about 40 pages)

2.1  Thermodynamic stability

·       Structure, role of the spontaneous curvature and of the curvature elasticity of the surfactant layer

·       Percolation

·       Exchanges, shape fluctuations

 

2.2  Phase diagrams

·       Emulsification failure and other solubility limits

·       "Fish" diagrams, critical points

 

2.3  Bicontinous microemulsions

·       persistence length of the surface layer

·       transition to lamellar phases or to molecularly dispersed phases

 

2.4  Ultralow interfacial tensions: origin, wetting phenomena

 

3.    Emulsions and foams (about 130 pages) 3.1  Emulsion and foam structures, analogies between high internal phase emulsions (HIPE) and foams, monodisperse dispersions

 

3.2  Foaming and emulsification: methods, control of drop/bubble size

 

3.3  Foam and emulsion rheology

·       Wall slip

·       Soft solid behavior, rejuvenation

·       Link with structural reorganisation processes, the jamming transition

·       Role of interfacial rheology

 

3.4  Foam and emulsion stability

·       Sedimentation/creaming of emulsions: influence of surface rheology, influence of surfactant concentration and of drop volume fraction. Foam drainage, case of HIPEs

·       Ostwald ripening: influence of surfactant concentration and of drop volume fraction.

·       Coarsening, structural reorganisation

·       Coalescence of bubbles/drops

o   Drainage of films between curved surfaces (Taylor/Reynolds regime), role of surface rheology, link with HLB, link with wetting. On the immobile surface condition. Dimpling instability

o   Film rupture (Vrij's model, other models)

o   Coalescence of many drops (Smoluchowski model)

·       Ultrastable emulsions and foams

 

3.5  Antifoams, defoamers, demulsifiers

 

4.    Similarities, differences between emulsions and foams, emulsions and microemulsions.(about 30 pages)

4.1  Why are bubbles larger than drops, why are emulsions longer lived than foams?

4.2  Foamed emulsions

4.3  Emulsion made with multiphase microemulsion systems

4.4  Solidification of the dispersions

 

5.    Industrial applications (about 20 pages)

5.1 Foams: detergency, food cosmetics, medicine, fire fighting, etc

5.2 Emulsions: food, cosmetics, pharmacy

5.3 Microemulsions: enhanced oil recovery, soil remediation, pharmacy, detergency