Flory—Huggins theory enthalpy change

The lattice model that served as the basis for calculating ASj in the last section continues to characterize the Flory-Huggins theory in the development of an expression for AHj . Specifically, we are concerned with the change in enthalpy which occurs when one species is replaced by another in adjacent lattice sites. The situation can be represented in the notation of a chemical reaction ... 

Having derived an expression for A5mfac, the second stage in the development of Flory-Huggins theory is to derive an expression for the effects of intermolecular interactions. In the original theory, this was considered only in terms of an enthalpy change, AJJ ix- Calculation of for polymer... 

The Flory — Huggins theory considers that the two components, i.e. solute and solvent, have identical local structures thus it does not take account of the influence of structural characteristics of components on the thermodynamic properties of the mixture. Therefore (a) the volume change at mixing, is zero and (b) the enthalpy of mixing may be assigned only to the differences in contact energies. 

The entropy and enthalpy change on mixing are, according to the modified Flory-Huggins theory, given by ... 

The classical Flory-Huggins theory assumes at the outset that there is neither a change in volume nor a change in enthalpy on mixing a polymer with a low-molecular-weight solvent [3-5] the influence of non-athermal 0)... 

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