Chromatographic behaviour of reversibly associating macromolecules. Part 1.—Theoretical model

Abstract

Block copolymers in selective precipitants form multimolecular micelles via closed association, which is characterized by an equilibrium between a unimer (molecularly dissolved copolymer) and micelles. A theoretical model is developed which accounts for: (i) relatively fast equilibration of the unimer between mobile and stationary phases, (ii) continuous perturbation and re-establishment of unimer ⇌ micelles equilibrium, and (iii) axial dispersion in the mobile phase during the passage of a solute through a column. This model describes quantitatively the behaviour of micellizing systems in size-exclusion chromatography. Chromatograms have been calculated for a wide range of association numbers and rates of association and dissociation. The results are compared with qualitative predictions of Coll's theory and Gilbert's theory of associating systems.