Solution Thermodynamics and Molecular Weights

The Waters/Micromass instrument determines absolute molecular weights and distributions. This instrumentation is not ideal for very high molecular weights, but at lower molecular weights may provide the exact molecular weight for each species present. 

A knowledge of solution thermodynamics is critically important in determining the suitability of a solvent for a molecular weight determination. Once having decided on a suitable solvent, solution thermodynamics provides a basis for determining how an extrapolation to zero concentration is to be carried out. 

Below the Flory 0-temperature, polymer solutions may phase-separate. The higher the molecular weight is, the higher the upper critical solution temperature. At infinite molecular weight, the Flory 0-temperature is reached. Thus the Flory 0-temperature is defined by several different criteria  

It is the temperature where the radius of gyration approximates that of the bulk polymer (see Chapter 5). 

It is the temperature at which an infinite molecular weight fraction would just precipitate (see Chapter 4). 

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