Thermodynamics of polymer mixtures

The compatibility of mixtures of homopolymers, mixtures of the same polymer differing in chain length, and mixtures of random copolymers is discussed from a thermodynamic standpoint. Small deviations from the Flory–Huggins combinatory entropy of mixing reveal themselves markedly in phase diagrams and second virial coefficients. Suitable experimental methods such as Pulse Induced Critical Scattering, neutron scattering, and low‐speed analytical centrifugation are discussed briefly. The molecular origins of phenomena discussed can at present best be traced for mixtures of homopolymers. The mutual influence the constituents exert on each other's chain flexibility seems to manifest itself in the shape of the miscibility gap. The other types of mixture allow less well developed theoretical description, due to lack of experimental data.