Polymers 4: Polyelectrolytes Flashcards
What are polyelectrolytes?
Polymers have ionisable functional groups (charged groups)
What are polybases, polyacids and polyampholytes also known as?
- Polybases: Cationics polyelectrolytes
- Polyacids: Anionic polyelectrolytes
- Polyampholytes: Amphoteric polyelectrolytes
What makes a weak anionic polyelectrolytes? And polymers with SO3- groups usually represent what?
- Weak: Carboxylic acid group attached
2. Represents spermacidal and viracidal properties
How do you ionise polyacrylic acid?
Adding a base
Give examples of an anionic polyelectrolyte?
- Poly (acrylic acid)
2. Heparin
Give examples of cationic polyelectrolytes?
- Chitosan (weak)
2. Polyethyleneimine
How do you protonate chitosan?
- Presence of acid causes NH2 group to protonate to NH3
Give examples of amphoteric polyelectrolytes?
- Carboxymethylchitosan
- Gelatin (derived from collagen)
- Proteins (BSA)
What is the isoelectric point?
- The pH at which the effective charge of the macromolecule is zero
- Usually where polymers precipitate
How can you tell when a amphoteric polyelectrolyte charge is zero?
When there’s a positive and negative charge that cancel each other out
What is viscosity?
The measure of a materials resistance to flow as a result of the internal friction of the material’s molecule
What are the different confrontation of macromolecules in solution?
- Globule
- Statistical coil
- Rigid rod
- Helix
What does confrontation depend on?
- Chain flexibility
2. Polymer to solvent interactions
As the confirmation of polymers go from unfolded chain to aggregates of macromolecules, what happens to the viscosity?
Decreases
Describe what Rheology is?
The deformation of structures when pressure is applied to them
What is newtons law equation?
- Shear stress (s-1)
- Applied stress (N)
- Dynamic (absolute) viscosity (Nm-2s)
How do you work out the relative viscosity of a solution?
t solution/ t solvent
How do you work out the specific viscosity?
(n solution - n solvent) / n solvent
How do you work out reduced viscosity?
Specific viscosity / C polymer
What is the Mark-Kuhn-Houwink equation and define each of the constants?
- [n] = K x Mv^alpha
- K and alpha are specific set of constants that are different for every polymer to solvent combination at a given temperature
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
- 0.5 is the ideal solvent for a flexible polymer
- 0.5 to 0.8 is a flexible polymer in good solvent
- 0.8 or more means stiff chain
What is a gel that’s made from polysaccharides?
- Alginate
2. Anionic Polysaccharide that’s extracted from brown algae
What are the properties of alginates?
- Made up of soluble potassium and sodium alginates in water
- Form physical gels in contact with divalent metal ions (calcium, strontium, zinc)
