Depletion stabilization and depletion flocculation

TLDR: In this paper, an approximate theory of depletion stabilization and depletion flocculation is presented based upon the rotational isomeric state-Monte Carlo procedures for calculating the conformation of macromolecules between two particles and the Flory-Huggins theory of polymer solutions.

Abstract: An approximate theory of depletion stabilization and depletion flocculation (i.e., stabilization and flocculation of colloidal particles by polymers in free solution) is presented. This is based upon the rotational isomeric state-Monte Carlo procedures for calculating the conformation of macromolecules between two particles and the Flory-Huggins theory of polymer solutions. It is shown that reasonable agreement between theory and experiment can be achieved for the critical volume fractions of polymer required to induce both depletion flocculation and depletion stabilization. The presence of adsorbed or attached polymer at the interface may have a significant effect on the onset of both flocculation and stabilization; this is especially true if the molecular weight of the attached chains is comparable to or greater than that of the free polymer. The effects of the steric chains, however, are reduced if the free polymer is significantly higher in molecular weight. Free energy minimization procedures are then necessary to calculate the polymer distribution between the plates. The agreement obtained between theory and experiment suggests that the theory incorporates the dominant factors that control depletion flocculation and stabilization.