Chapter 13: Study Guide and Self-Assessment
Having discussed solution properties we are now in a position to consider methods for the determination of molecular weight. This is a fundamental characteristic of polymer materials and the ultimate source of their interesting and in some cases (e.g., rubber elasticity) unique properties. The methods used to determine molecular weight can also be used to determine things like polymer/solvent interaction parameters and the radius of gyration of polymer chains, so what is covered in this chapter is some essential, basic polymer physical chemistry.
Objectives
Upon successfully completing this chapter you should gain:
- A knowledge of the four principal methods used to determine the molecular weight of polymers and the average (number, weight, etc.) determined by each.
- An understanding of osmotic pressure, how it is used to determine number average molecular weight and the relationship to the chemical potential of the solvent.
- An understanding of how light scattering can be used to measure weight average molecular weight and an ability to construct a Zimm plot.
- A familiarity with the use of solution viscosity measurements and the Mark-Houwink-Sakaruda equation to determine a viscosity average molecular weight.
- An understanding of how size exclusion chromatography (SEC) can be used to separate molecules according to their size.
- A familiarity with the concept of an equivalent hydrodynamic sphere, the universal calibration curve and the use of SEC to determine long-chain branching.
Self-Assessment Questions