Thermodynamic aspects of the partitioning of a solute in a gel–solvent system

An expression is derived for the partitioning of a solute molecule in a two-phase system: swollen gel and free solvent. The approach is thermodynamic, and no specific mechanism for the accessibility of the solute to the gel is assumed. Instead, general interaction terms between the components, i.e., polymer–solvent–solute, are introduced.