Thin "soft" films and colloidal stability

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"It may be said that studies of the coagulation resistance of colloids have been responsible for the creation of a new science - the science of surface forces and their manifestations in the properties of thin (but polymolecular) layers. In turn, research in this new field of knowledge has contributed to neighboring sciences: studies of molecular forces, liquid crystals, electrochemistry, mass transport theory, certain branches of nonequilibrium thermodynamics, biophysics, hydraulic engineering, and soil science and the science of the earth's crust. It is natural, therefore, to combine in one book the problems of colloid stability and the stability of thin films."

B.V. Derjaguin, Theory of stability of colloids and thin films, Consultants Bureau: New York; 1989.


Surface energies

Attraction - Dispersion energies

Repulsion - Steric(entropic)

Repulsion - Electrocratic

Repulsion - Electrosteric

Food as soft matter

Spinodal decomposition

Extended Reading

  • Derjaguin (1989)
    • Chapter 1. Historical review
      • "A distinction is frequently made between colloidal and disperse systems. This distinction is not only arbitrary, but also unimportant, generally speaking: Colloidal particles are distinguished from other disperse systems only in that their particles are smaller. It is logical to combine them into a single class that we will term 'disperse systems', recognizing an upper limit (also, of course, arbitrary) above which the particles are large and there is little development of the interface." p. 1
      • The difference between disperse systems and "true" solutions lie in the instability of the disperse systems. p. 1
    • Chapter 2. Basic types of stability of colloidal systems
      • Because colloidal solutions have an extra degree of freedom (the particle distribution with respect to mass) when compared to ordinary solutions, the stability of disperse systems may be changed in ways not characteristic for solutions. p. 19
      • Three types of colloidal stability:
        • "Phase stability, or stability with respect to layer separation which produces a system with a different number concentration of particles, a system that is capable of coexistence with the original system." An example of layer separation is the phenomenon of coacervation. p. 19
        • "Stability of disperse composition, or stability with respect to change in dispersity, in the general case invariance of the particle size and distribution." This type of stability is impossible if the phase consists of a single component. p. 20
        • Aggregative stability is the most characteristic of colloidal systems. It can be of two types: stability due to a coagulation rate so slow as to be negligible and aggregative stability due to a balancing of aggregation and deaggregation processes. p. 20
    • Chapter 3. Equilibrium and disjoining pressure of thin layers
  • Napper
    • Chapter 2. Stabilization by attached polymer: Steric stabilization
    • Chapter 7. Thermodynamically limited steric stabilizations
    • Chapter 15. The effects of free polymer on colloidal stability
  • Norde
    • Chapter 16. Stability of lyophobic colloids against aggregation
      • "We define colloidal systems as systems in which particles dispersed in a medium are subjected to both thermal motion and motion due to external forces (e.g. gravity)." p. 313
      • "Colloidal stability refers to the ability of a dispersion to resist aggregation into larger entities that then would segregate form the medium." p. 313
  • Russel (1987)
    • Chapter 2. Flocculation or equilibrium phase separation?
  • Russel (1989)
    • Chapter 6. Forces due to soluble polymer
    • Chapter 9. Polymeric stabilization

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