Basic Polymer Properties

Question 1

Define MACROMOLECULES

Answer 1

Molecules composed of a large number of atoms

Question 2

Define POLYMER

Answer 2

substances of a high molecular weight consisting of repeating monomer unit

Question 3

What are the 5 different polymer structures?

Answer 3

1. HOMOPOLYMER
2. ALTERNATING POLYMER
3. RANDOM COPOLYMER
4. BLOCK COPOLYMER
5. GRAFT COPOLYMER

Question 4

What are the physiochemical properties of polymers?

Answer 4

• chemical reactivity largely depends upon: monomers, e.g. function groups present
• Physical properties depends upon: arrangement of the monomer, how the polymer chains interact with each other and the environment

Question 5

Polymer Molecular Weight

• Number average molecular weight
• Weight average molecular weight
• Viscosity average molecular weight

Answer 5

- Number average molecular weight (Mn)
population of N molecules consisting of:
- n1 molecules of molecular weight 1
- n2 molecules of molecular weight 1
sumniMi/sumni
- Weight average molecular weight (Mw)
population of molecules where:
- m1 mass of molecules of molecular weight M1
- m2 mass of molecules of molecular weight M2
sumniMi2/ sumniMi 
- Mw > Mn

Question 6

Define polydispersity

Answer 6

If a polymer is polydisperse, it contains a range of molecular weights

Question 7

What are the techniques used to characterise polymers?

Answer 7

1. light scattering can be used to measure polymer molecular weight and hydrodynamic radius.
2. Viscosity and flow examine flow properties and polymer shape.
3. Analytical ultracentrifugation separates polymers according to the molecular weight.
4. Gel electropheresis separates polymers according to charge and molecular weight.
5. Nuclear magnetic resonance
6. Differential scanning calorimetry used to examine interactions between polymer chains
7. Gel permeation chromatography can separate polymers according to molecular weight.

Question 8

What are water solubility polymers able to do?

Answer 8

• increase the viscosity of solvents
• swell/change in solution
• Adsorb at surfaces
• These make it useful as suspending agents
• Insoluble polymers are often capable of forming thin films and are used in tablet coating, wound dressings and membranes
• the rate of dissolution is dependent on molecular weight
• High mol weight= stronger forces holding chains together