Free energy and osmotic pressure

Let J00, Jllt and J01 be the energies that can be associated respectively to solvent-solvent, solute-solute, and solute-solvent contacts. The change of energy which takes place when the solute is dissolved in the solvent can be characterized by the quantity 

For x 0, we have a repulsive solute-solvent interaction which amounts to an attraction between chains, and this repulsion counterbalances the excluded volume effects. 

the energy associated with the solution is approximately (to a constant and in thermal units 1/ff) 

Indeed, each point of a polymer chain (there are NN of them) may have (t — 2) contacts with the solvent. 

From (8.2.6) and (8.2.8), we immediately derive the free energy which will be expressed in thermal units 1 //  

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