Steric stabilization

Question 1

How can uncharged polymers be attracted onto particle surfaces?

Answer 1

~ weak van der waals forces
~ connection can occur over multiple points along the polymer chain

Question 2

How does repulsion occur?

Answer 2

~ as polymer-coated particles approach, polymer chains overlap, causing repulsion

~ repulsion is entropy-based (osmotic pressure) as overlap decreases the number of available polymer conformations

Question 3

What do homopolymers do? (ex: polystyrene)

Answer 3

~ especially when dilute, can bridge between two particles facilitating bridging flocculation

Question 4

How can you overcome bridging flocculation?

Answer 4

~ the use of block or graft copolymers

~ relatively insoluble in the liquid, anchors onto the paticle surface, the other is soluble in the liquid

~ polymers in free solution can also inhibit flocculation by osmotic pressure

Question 5

How is the solubility of polymer enhanced in liquid?

Answer 5

~ by increasing temp

~ at lower temp, chains are more mutually attracted, collapsing the chains toward the particle surface, impeding steric hinderance

Question 6

What is the θ temp?

Answer 6

~ the transition from one behavior to another over a narrow temp range

Question 7

When is steric stabilization typically used?

Answer 7

~ in non-polar solvents
~ paints, inks, and coatings