To determine if the parameters of two molecules (usually a solvent and a polymer) are within range, a value called interaction radius (
gives the relative energy difference (RED) of the system: Historically Hansen solubility parameters (HSP) have been used in industries such as paints and coatings where understanding and controlling solvent–polymer interactions was vital.
Over the years their use has been extended widely to applications such as: HSP have been criticized for lacking the formal theoretical derivation of Hildebrand solubility parameters.
In particular, all solubility parameter-based theories have a fundamental limitation that they apply only to associated solutions (i.e., they can only predict positive deviations from Raoult's law): they cannot account for negative deviations from Raoult's law that result from effects such as solvation (often important in water-soluble polymers) or the formation of electron donor acceptor complexes.
Part B: Polymer Physics 26(4), 785-79, 1988) where the regions of solubility are far more eccentric than predicted by the standard Hansen theory.
the polar and hydrogen bonding parameters cannot reliably be partitioned in a manner that is compatible with Hansen's values.