Effect of Nonadsorbing Polyelectrolytes on Colloidal Interactions in Aqueous Mixtures

Sharma, Amber; Tan, Su Nee; Walz, John Y.

doi:10.1006/jcis.1997.4940

Cited by 74 publications

(72 citation statements)

References 57 publications

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“…It should be emphasized, however, that this theory is valid only in first order of n. In contrast, large deviations, e.g., even repulsive parts of the depletion potential, are predicted if correlation effects between macromolecules are taken into account [5,6]. The magnitude of depletion forces for small concentrations n is typically on the order of nano-or piconewtons; therefore experimental techniques like surface forces apparatus [7], atomic force microscopy (AFM) [8], or total internal reflection microscopy [9] (the latter is also used in the present study and will be discussed in more detail below) are required for direct measurements of Eq. (1).…”

Section: Fakultät Für Physik Universität Konstanz D-78457 Konstanzmentioning

confidence: 99%

“…According to a force balance model the magnitude and the range of the depletion forces are then predicted to be largely increased due to electrostatic repulsion [10]. In fact, most of the direct measurements of depletion forces were performed on solutions of highly charged macromolecules like cetyltrimethylammonium bromide micelles [7], charged silica spheres [11], or polyelectrolytes [9].…”

Section: Fakultät Für Physik Universität Konstanz D-78457 Konstanzmentioning

confidence: 99%

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Direct Measurement of Depletion Potentials in Mixtures of Colloids and Nonionic Polymers

1998

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In colloidal suspensions containing a binary mixture of hard spheres depletion forces occur which substantially contribute to the interaction of the larger spheres among themselves and a wall, respectively. We investigated the depletion force acting on a large colloidal polystyrene sphere immersed in a solution of small, noncharged polymer coils close to a flat glass surface by means of total internal reflection microscopy. When the distance between the polystyrene sphere and the wall is smaller than the diameter of the polymer coils, an attractive potential acting on the sphere is observed which depends strongly on the polymer concentration. Our results are in agreement with theoretical predictions.[S0031-9007 (98) The stability of colloidal mixtures consisting of larger and smaller particles is well known to be strongly influenced by entropic depletion forces. Accordingly, those forces are essential in understanding phase separation phenomena and flocculation of binary hard-sphere mixtures, colloids in the presence of micelles, and of colloid polymer mixtures [1,2]. Very recently, it was suggested that depletion forces even may play an important role in the shape changes of phospholipid vesicles [3].The principal phenomenon of depletion interaction is easily understood when, e.g., a hard sphere of radius R suspended in a fluid containing smaller spheres of radius r (the latter are referred to as macromolecules in the following) in front of a wall at distance z is considered (see Fig. 1). If z decreases below the diameter of the macromolecules they are expelled from the region between the sphere and the wall. Consequently, the concentration of macromolecules becomes depleted in this region compared to that of the bulk, and an effective osmotic pressure causing a net attraction between the sphere and the wall occurs. Such an attractive force is also observed when the wall is replaced by another hard sphere.The first quantitative explanation of this effect was given by Asakura and Oosawa [4]. According to their calculation the change in the Helmholtz free energy DF of a single sphere positioned at distance z from a wall and suspended in a fluid of macromolecules can be written as

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Section: Fakultät Für Physik Universität Konstanz D-78457 Konstanzmentioning

confidence: 99%

Section: Fakultät Für Physik Universität Konstanz D-78457 Konstanzmentioning

confidence: 99%

Direct Measurement of Depletion Potentials in Mixtures of Colloids and Nonionic Polymers

1998

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“…As two colloidal particles move closer together, the concentration of the smaller particles surrounding the larger particles is altered. This creates a lower osmotic pressure relative to the bulk solution, which creates an attractive force between the larger colloidal particles [14,16].…”

Section: Introductionmentioning

confidence: 99%

“…For example, depletion flocculation experiments using sodium polystyrene sulfonate (SPSS) as a non-adsorbing macromolecule in solution with colloidal polystyrene particles has been reported have been done by Walz and coworkers [12,16]. Critical flocculation concentrations of SPSS in solutions of 473 nm colloidal polystyrene particles (at 0.01%v) reported to approximately 0.2%w SPSS.…”

Section: Introductionmentioning

confidence: 99%

Stabilization of Weakly Charged Microparticles Using Highly Charged Nanoparticles

Herman

Walz

2013

Langmuir

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An experimental investigation was conducted to evaluate the possible use of highlycharged spherical nanoparticles to stabilize an aqueous dispersion of weakly-charged microspheres. At low pH values, the surface of silica is weakly charged, which leads to flocculation of colloidal suspensions of silica microspheres. Binary solutions of weakly charged silica microspheres and highly charged polystyrene latex nanoparticles result in adsorption of the nanoparticles onto the surface of the silica microspheres. This effectively "recharges" the silica spheres, with effective zeta potentials increased to the range that is unfavorable for flocculation of microspheres in a silica-only solution. However, this does not guarantee stability, and comparisons between positively charged amidine latex nanoparticles and negatively charged sulfate latex nanoparticles indicate that the degree of coverage plays an important role in the restabilization. The sulfate latex nanoparticles do not cover the surface sufficiently, and though they seemingly provide sufficient charge, the weakly charged patches of the exposed silica substrate can lead to flocculation. The amidine latex nanoparticles, on the other hand, cover the surface more completely, and effectively prevent flocculation of the silica microspheres. The mechanisms responsible for this different adsorption and stabilizing behavior are not entirely understood, as both the amidine and sulfate latex nanoparticles are of similar size and the magnitude of the zeta potentials of the different particle types are comparable.iii

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“…16 In this technique the particle-surface distance can be derived from the intensity of an evanescent wave that is formed when a photon beam is reflected from a surface at a sufficiently large incident angle. TIRM has been used by Walz and co-workers [17][18][19] to study depletion interaction.…”

Section: Introductionmentioning

confidence: 99%

Polymer-Mediated Interaction between a Plate and a Sphere

2001

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A recently developed method is applied to calculate the depletion interaction between a sphere and a flat plate due to nonadsorbing ideal polymers for arbitrary polymer-sphere ratios. The interaction potential is calculated from the polymer concentration profiles surrounding the sphere and plate based on the adsorption around the particles. The polymer concentration profile in the space near the two particles is the product of the polymer concentration profile due to the single plate and its profile around the single sphere. The product function profile is in good agreement with profiles calculated by computer simulations. The interaction potential derived from the adsorption using the product function agrees with analytical results for infinitely small and large spheres. It is shown that the force between a flat plate and a sphere goes to a minimum for large polymer-colloid ratios. These results show that a product function applies to the sphere-plate geometry and facilitates the calculation the depletion interaction between colloidal particles in complex cases.

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Effect of Nonadsorbing Polyelectrolytes on Colloidal Interactions in Aqueous Mixtures

Cited by 74 publications

References 57 publications

Direct Measurement of Depletion Potentials in Mixtures of Colloids and Nonionic Polymers

Direct Measurement of Depletion Potentials in Mixtures of Colloids and Nonionic Polymers

Stabilization of Weakly Charged Microparticles Using Highly Charged Nanoparticles

Polymer-Mediated Interaction between a Plate and a Sphere

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