where / and x are the volume fractions and mole fractions, respectively,
and v12 is the Flory interaction coefficient. It may be noted
that there is a relation between Flory interaction coefficient and
the relative energy difference (RED) number, which has been
defined as the distance (according to Ra) divided by Ro. Ro is the
maximum difference in affinity tolerable for the solution to take
place. vc is usually taken as being near 1/2 for polymers of very
large molecular weight.