On an alternative form for the free energy of a single polymer chain in solution

The free energy of an isolated polymer chain in solution is decomposed into a sum of three terms. It is shown that one of these terms is the Flory ‘‘elastic’’ contribution to the free energy; the other terms originate from chain segment–segment interactions of any order. This decomposition of the free energy in a sum of terms is valid whatever the quality of the solvent. The relative importance, as a function of temperature, of the Flory elastic and of the nonelastic terms is not presently elucidated. It may however be shown that in the two limits of the perfect nonsolvent and the ideally good solvent the elastic term vanishes. An application to the chain collapse problem is suggested.