D5 Basic Polymer Properties 1 Flashcards
What are macromolecules?
Molecules composed of a large number of atoms
What are polymers?
Substances of high molecular weight consisting of repeating monomer units
What is a homopolymer?
Same repeated monomers
What is an alternating copolymer?
Repeating alternative monomers
What is a random copolymer?
Monomers that are randomly arranged rather than alternating or patterned
What is a block copolymer?
Where there are sequences of monomers e.g. 4 of the same, 4 different of the same etc
What is a graft copolymer?
Stem chain of the same monomers, with branched off chains of the same polymers
What affects the chemical reactivity of polymers?
Monomeric unit(s)
What affects the physical properties of polymers?
Arrangement of the monomers
How the polymer chains interact with each other/or the environment
How can polymer Mr be measured other than molecular weight?
Viscosity measurements of polymer solutions can be used to determine a viscosity average molecular weight (Mv)
What is polydispersity?
Describe the arrangement?
If a polymer is polydisperse, it contains a range of molecular weights.
Can be arranged “randomly” or “block”
How can we calculate the degree of polydispersity?
Mw / Mn
What techniques can be used to characterise polymers?
- Light scattering techniques can be used to measure molecular weight and hydrodynamic radius (of gyration)
- Viscosity and rheological (flow) techniques examine flow properties and polymer shape
- Analytical ultracentrifugation seperates polymers according to molecular weight
- Gel electrophoresis
- Nuclear magnetic resonance (conformation in solvent and structure)
- Gel permeation chromatography can seperate polymers according to molecular weight
How does gel electrophoresis seperate polymers?
Gel electrophoresis seperates polymers according to charge and molecular weight
Why is it not normally possible to state a single molecular weight for a polymer?
Due to polydispersity
