Deck B Flashcards
van der Waals forces
transient, weak electrical attraction of one atom for another. They originate from dipole or induced-dipole interactions at the atomic and molecular level.
Types of van der Waals
Keesom, Debye, London
always attractive at atomic and molecular level but can be repulsive at colloidal level
Keesom interaction
dipole-dipole interaction
Debye interaction
dipole-induced dipole interaction
London interaction
induced-induced dipole interaction
Electric double layer
formed in order to neutralize the charged surface and causes an electrokinetic potential between the surface and liquid
Steric force
mainly induced by polymers, polyelectrolytes or biomacromolecules that are adsorbed or grafted onto the surface of colloidal objects
long-ranged
Radius of gyration
the area that a floating hydrophobic tail will cover when the head is static
Factors affecting steric forces (3)
Coverage of polymer on each surface
Reversible adsorption or irreversible grafting onto the surface
Quality of the solvent (if tails will expand or compact in it)
Steric force (alt)
arise when the polymer chains overlap which confine the dangling polymer chains and causes a repulsive entropic force or overlap repulsion
Bridging Flocculation
when high molecular weight polymers adsorb to 2 colloids at each end
Depletion Flocculation
polymer is squeezed out between two colloids causing an osmotic pressure difference
What does the strength of the depletion force depend on?
Concentration and molecular weight of polymers
Why are solvation forces generated when two surfaces are brought close together?
The molecules line up long-ways and then a row is squeezed out, then they line up again and …
What physical factors does the solvation force depend on? (Solvent)
shape, size and polarity of solvent molecule
