On the effect of pressure and temperature on the zero angle scattering by mixtures containing polymers

Phase diagrams of polymer blends and solutions are usually studied by measuring the scattered intensity (by light or neutrons) as a function of composition, temperature and pressure. If one expands Flory's chi parameter as a function of the composition, one sees that in order to have deviations from Flory's laws, thermodynamic quantities such as volume, heat capacity or compressibility should vary with respect to composition by a power law of degree larger than two. In some cases, the direct measurement of these quantities could lend to a more precise and rapid determination of the miscibility conditions. (C) Academie des sciences/Elsevier, Paris.