Florys athermic solution model

Flory s model applies to an athermic solution, meaning that the excess molar enthalpy is null, so the excess molar Gibbs energy is simply written as follows, in light of relation [3.125]  

For a binary solution, we use the excess partial molar Gibbs energy to deduce the activity coefficient of a component /  

In particular, at infinite dilution, we obtain the activity coefficient of each of the two components of a binary by making b = 0 for that of component A and a = 0 for that of component B. This gives us  

In this model, we have not taken account of the energetic interactions between the molecules. For precisely this reason, such as model is well suited for solutions of polymers, as the intermolecular energy values are very low indeed in these solutions. Table 3.1 shows that the deviation from ideal state grows very rapidly as the pol5mier chain length Vs increases. 

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The term general solution was introduced by Flory to characterize polymer solutions whose enthalpy of mixing is not zero. The model of general solutions borrows the formula of excess enthalpy from regular systems and the excess entropy from athermal solutions. Thus, a treatment of non-ideal polymer solutions arises which is simpler than the conventional methods applied to real systems this allows the deduction, on the basis of the known relationships, of the expressions of functions of deviation from ideality. Thus, for the activity coefficients of components in a binary system the following relations were established ... 

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