Solubility of amorphous polymers good and poor solvents

2 Solubility of the amorphous polymers good and poor solvents 

Let us now consider the properties of amorphous polymers with respect to solvents. Is it possible to extrapolate the results obtained before for mixtures of small molecules The answer is no, and we shall see in this book, that the energies and entropies of mixing are expressed in a manner which differs considerably from the one used in the preceding section. 

Even in the case where the polymer is soluble for all proportions in the solvent, it is possible to distinguish two situations corresponding to differences in the swelling of the chain. In a poor solvent the chain is only slightly swollen. In a good solvent , the chain is very swollen and has very different and peculiar properties. On the other hand, it is incorrect to assume that formulae (1.2.2) and (1.2.9) remain valid for chains. 

However, one could think of representing the energy of mixing in a form analogous to (1.2.7) 

On the other hand, the chain entropy (per link) is, of course, smaller than that of small molecules nevertheless, the entropy of very flexible chains remains large. In brief, the chains are less soluble than the corresponding monomers and their solubility diminishes when their molecular mass increases. 

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