Stavermans corrective factor

In the above model, we chose linear polymer molecules and molecules of solvent which are much smaller than those of the pol5mier, so that every part of the pol5mier was in the vicinity of molecules of solvent. 

We shall now introduce two fundamental parameters of the molecules which are used in the models of molecular solutions discussed below. These two parameters are  

The choice of standard is arbitrary. Frequently, we use the Abrams and Prausnitz standard [ABR 95] a linear molecule of polyethylene of infinite length, which conforms to the following equation  

the structural parameters are calculated on the basis of the two relations  

Staverman uses Flory s model as a starting point, but introduces a form factor in the number of complexions, taking account of the fact that the molecules are only in contact at their surfaces. This enables him to construct a new expression for number of possibilities of introducing the molecule of polymer and the molecules of solvent. Thus, the excess molar entropy term of conformation is altered, and becomes  

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Staverman examined the problem of representing a solution in which the molecules are no longer linear, and therefore a certain amount of the molecule would not be exposed to the molecules of solvent, because they would be isolated inside the molecule of solute. These imprisoned sites receive no molecules of solvent. Figure 3.5 gives a 2D representation of the exclusion of certain sites (shaded) which are no longer able to receive molecules of solvent as near neighbors. This introduces a corrective factor relating to the surface of the molecule. 

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