The mean field, rigid lattice treatment as applied to polymer mixtures
has been used to estimate segment-segment interaction parameters for
a wide range of polymers. These parameters incorporate, without distin
ction, contributions from non-combinatorial entropy effects, dispersio
n forces and any specific interactions that operate in the polymer ble
nd. Thus while these parameters can be used to predict successfully th
e nature of the phases in untested polymer blends, structural effects
may also play a role in determining miscibility, and these may have to
be assessed individually. Examples of structural effects are describe
d using chlorine-containing polymers and blends of copolymers with an
anhydride ring attached in two different ways to the polymer chain. Th
e extension of binary interaction parameters to the prediction of phas
e behaviour in complex ternary copolymer blends and the effect on the
phase behaviour of changing the component ratios in the blends, is als
o illustrated.