Polymers 4: Polyelectrolytes

Question 1

What are polyelectrolytes?

Answer 1

Polymers have ionisable functional groups (charged groups)

Question 2

What are polybases, polyacids and polyampholytes also known as?

Answer 2

1. Polybases: Cationics polyelectrolytes
2. Polyacids: Anionic polyelectrolytes
3. Polyampholytes: Amphoteric polyelectrolytes

Question 3

What makes a weak anionic polyelectrolytes? And polymers with SO3- groups usually represent what?

Answer 3

1. Weak: Carboxylic acid group attached

2. Represents spermacidal and viracidal properties

Question 4

How do you ionise polyacrylic acid?

Answer 4

Adding a base

Question 5

Give examples of an anionic polyelectrolyte?

Answer 5

1. Poly (acrylic acid)

2. Heparin

Question 6

Give examples of cationic polyelectrolytes?

Answer 6

1. Chitosan (weak)

2. Polyethyleneimine

Question 7

How do you protonate chitosan?

Answer 7

1. Presence of acid causes NH2 group to protonate to NH3

Question 8

Give examples of amphoteric polyelectrolytes?

Answer 8

1. Carboxymethylchitosan
2. Gelatin (derived from collagen)
3. Proteins (BSA)

Question 9

What is the isoelectric point?

Answer 9

1. The pH at which the effective charge of the macromolecule is zero
2. Usually where polymers precipitate

Question 10

How can you tell when a amphoteric polyelectrolyte charge is zero?

Answer 10

When there’s a positive and negative charge that cancel each other out

Question 11

What is viscosity?

Answer 11

The measure of a materials resistance to flow as a result of the internal friction of the material’s molecule

Question 12

What are the different confrontation of macromolecules in solution?

Answer 12

1. Globule
2. Statistical coil
3. Rigid rod
4. Helix

Question 13

What does confrontation depend on?

Answer 13

1. Chain flexibility

2. Polymer to solvent interactions

Question 14

As the confirmation of polymers go from unfolded chain to aggregates of macromolecules, what happens to the viscosity?

Answer 14

Decreases

Question 15

Describe what Rheology is?

Answer 15

The deformation of structures when pressure is applied to them

Question 16

What is newtons law equation?

Answer 16

1. Shear stress (s-1)
2. Applied stress (N)
3. Dynamic (absolute) viscosity (Nm-2s)

Question 17

How do you work out the relative viscosity of a solution?

Answer 17

t solution/ t solvent

Question 18

How do you work out the specific viscosity?

Answer 18

(n solution - n solvent) / n solvent

Question 19

How do you work out reduced viscosity?

Answer 19

Specific viscosity / C polymer

Question 20

What is the Mark-Kuhn-Houwink equation and define each of the constants?

Answer 20

1. [n] = K x Mv^alpha
2. K and alpha are specific set of constants that are different for every polymer to solvent combination at a given temperature

Question 21

What does it mean in the Mark-Kuhn-Houwink equation when the alpha value is equal to 0.5, between 0.5 and 0.8, and

Answer 21

1. 0.5 is the ideal solvent for a flexible polymer
2. 0.5 to 0.8 is a flexible polymer in good solvent
3. 0.8 or more means stiff chain

Question 22

What is a gel that’s made from polysaccharides?

Answer 22

1. Alginate

2. Anionic Polysaccharide that’s extracted from brown algae

Question 23

What are the properties of alginates?

Answer 23

1. Made up of soluble potassium and sodium alginates in water
2. Form physical gels in contact with divalent metal ions (calcium, strontium, zinc)