Small mesoscopic particles in dilute and semidilute solutions of nonadsorbing polymers

Abstract

Polymer-induced interactions between two small mesoscopic particles of radius R and between a particle and a wall are investigated for dilute or semidilute embedding solutions of long flexible nonadsorbing polymer chains with radius of gyration R g . Asymptotically exact predictions are obtained using a ''small radius expansion,'' to express the interactions in terms of properties of the polymer solution without particles. The nonmonotonic dependence of the second virial coefficient B 2 CC of a dilute suspension of particles on the interchain overlap is discussed in detail. The magnitude of the minimum of B 2 CC /R 3 increases as a power law in R g /R. The exponent and amplitude are quite different from the earlier prediction of an integral-equation approach. For dilute polymers in two dimensions outside two circular disks in contact, exact results are given for the monomer-density depletion profile, the pressure variation along the perimeter of, and the polymer-induced force between the two disks.

Polymer induced depletion potentials in polymer-colloid mixtures

“…Both RG theory 34 and integral equation approaches 71,31 predict that for large enough q, B * 2 should go through a minimum as a function of ρ/ρ * , although the two theories differ significantly on quantitative details. Experiments seem to show similar effects 66 .…”

“…when the colloids are much smaller than the polymers, other approaches, which treat the polymers on a monomer level, are more relevant. Examples include integral equation techniques 31 , scaling theory 32,33 , or renormalization group theory (RG) 34 . In this paper we concentrate on the regime where R g is of the order of R c or smaller.…”

Excluded-volume polymer-induced depletion interaction between parallel flat plates

“…The inclusion of the excluded-volume effects of the polymer segments has gained increasing attention [8][9][10][11][12][13][14][15][16][17][18] in order to bring the theoretical description closer to real polymer chains. Simplifications can be made in a successful way when relatively small colloidal spheres immersed in a polymer solution are considered [8][9][10][11], whereas a meanfield approach was developed for excluded-volume polymers between two plates [12].…”

“…Simplifications can be made in a successful way when relatively small colloidal spheres immersed in a polymer solution are considered [8][9][10][11], whereas a meanfield approach was developed for excluded-volume polymers between two plates [12]. For more complex systems, reference interaction site models (RISM) have been developed [13][14][15][16] that treat the polymers more realistically than PHS models do.…”

Flory-Huggins theory for athermal mixtures of hard spheres and larger flexible polymers

“…The interactions between colloidal spheres and polymer molecules have been studied theoretically via a number of techniques: scaling approaches [8][9][10], field theory [11][12][13][14], computer simulation [15,16], integral equations [17,18], and other approaches [19][20][21][22]. The phase behaviour has been studied via computer simulation [15], scaling theory [23], and perturbation theory [24,25], where Refs.…”