The secondary minimum in a classical DLVO potential curve is often at a relatively large surface-to-surface (or center-to-center) inter-particle distance.
My question is: How can particles trapped in a secondary potential well be reversibly agglomerated (i.e., held together by weak forces in a flocculated state) despite being at a non-zero inter-particle separation distance? Doesn't agglomeration require the surface-to-surface separation to be zero (i.e., contact between particles) in order to take place? In other words, how would two flocculated particles look like when trapped in a secondary minimum?
The total potential energy of two particles has a secondary minimum when the particles are separated by a film with elastic and strength properties. If this film is destroyed by the action of ultrasound or by the addition of a solvent, the particles come into contact and aggregate. The theory of DLVO between particles corresponds to the theory of the potential of the average force between molecules.
The potential of the average force between two molecules during hydrophobic interaction has two minima on contact and at a distance of the diameter of the water molecule. Therefore, there may be contact and water-separated hydrophobic interaction. Therefore, we believe that the micelle of ionic surfactants has dual properties. There is a contact micelle and a micelle with surfactant molecules separated by water molecules. They oscillate. This theory is developed in our work. I attach one file. Other articles can be found in my profile.
Article Contact and water-separated hydrophobic interactions in mice...
Thixotropy is a great example of this. Non-drip paints exploit the particles being held in the secondary minimum when static. The energy introduced by the shear of a brush or roller is enough to pull the particles out of the minima.
The key is that the depth of the secondary minimum is similar to the external energy that will be provided. This can be mechanical, acoustic, thermal etc.
Energies are usually expressed in units of kT.
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