Polymer Polydispersity Effect on Depletion Interaction between Colloidal Particles

Abstract

The effect of polymer polydispersity on the polymer‐induced interaction between colloidal particles due to non‐adsorbing ideal chains is investigated. An analytical theory is developed for the polymer‐segment density between two plates and in the space surrounding two spheres by extending a recently proposed superposition approximation to include polymer polydispersity. Monte Carlo computer simulations were made to test the validity of the analytical theory. The polymer densities predicted by the superposition approximation are in reasonable agreement with simulation results for the polydisperse case. The simulations show that depletion leads to a size fractionation of the polymers. It is shown that size polydispersity has a small effect on the interaction between two parallel plates but a more significant effect on the interaction between two spheres. The range of the potential increases and the contact potential drops with increasing polydispersity.

Influence of polymer shape on depletion potentials and crowding in colloid–polymer mixtures

“…The close agreement of depletion potentials from our simulations of the ellipsoidal polymer model with, on the one hand, DFT calculations and simulations for explicit polymer models and, on the other hand, experimental data from optical tweezer measurements of colloid-DNA mixtures is strong evidence that aspherical polymer shapes play a significant role in depletion. Contrary to previous studies, 1,19,25 we conclude that depletion interactions between hard-sphere colloids are not fully captured by modeling polymers simply as penetrable spheres of an effective size or, equivalently, with an effective depletion layer thickness. Moreover, our approach consistently accounts for fluctuations in polymer shape, in contrast to models of spheroidal depletants.…”

Mean-field models of structure and dispersion of polymer-nanoparticle mixtures

“…Lekkerkerker, Tuinier and coworkers 66,[84][85][86][87] have pioneered the Gibbs adsorption and free volume theories to develop the phase diagrams for mixtures of colloids of different geometrical shapes in both ideal and interacting polymer solutions. Also, alternative approaches invoking perturbation theories, 88 and cell models 89 have been used to predict the phase behavior of nanoparticle-polymer solutions characterized by depletion interactions.…”

Effective interactions in polydisperse colloidal suspensions investigated using Ornstein–Zernike integral equations

“…This issue became the subject of experimental [23], and theoretical [37][38][39] efforts. Using density functional theory Goulding and Hansen [40] examined depletion interactions between big hard spheres immersed in a polydisperse bath of smaller particles.…”