Depletion Attraction Caused by Unadsorbed Polyelectrolytes

Pagac, Edward S.; Tilton, Robert D.; Prieve, Dennis C.

doi:10.1021/la980058f

Cited by 56 publications

(64 citation statements)

References 33 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…The main features of these data have been discussed in detail by a number of authors. [37][38][39][40][41]44 In this study, these data are simply used as a reference point for comparison to the data collected in the presence of the polyelectrolyte, and so no further discussion will be presented here.…”

Section: Resultsmentioning

confidence: 99%

Oscillatory Packing and Depletion of Polyelectrolyte Molecules at an Oxide−Water Interface

2002

Self Cite

View full text Add to dashboard Cite

Total internal reflection microscopy (TIRM) has been used to study the interactions between a 5 µm borosilicate glass sphere and a silica slide in the presence of a nonadsorbing polyelectrolyte, sodium (polystyrene sulfonate) (NaPSS). The effect of the polymer concentration, within the dilute solution regime, on the observed interactions was investigated. In all cases, the interactions displayed a short-range electrostatic repulsion followed immediately, at larger separations, by a decaying oscillatory interaction that is attributed to structuring of the polyelectrolyte in solution. The periodicity of the oscillations, as a function of concentration, indicates that at large surface separations the polymer chains are ordered as a nonintermixing, space-filling, latex. At polymer concentrations of between 200 and 1000 ppm, a transition to a system of ordered rods, parallel to the interface was seen for the final layer of polymer molecules.

show abstract

Section: Resultsmentioning

confidence: 99%

Oscillatory Packing and Depletion of Polyelectrolyte Molecules at an Oxide−Water Interface

2002

Self Cite

View full text Add to dashboard Cite

show abstract

“…The volume fraction of nanoparticles associated with the settled microspheres was calculated from the difference of the initial [Zr bulk ] and supernatant [Zr] values, as determined by inductively coupled plasma analysis. In addition, scanning angle reflectometry (27,28) was carried out to probe the adsorption behavior of nanoparticle species onto a model silica surface (i.e., an oxidized silicon wafer). Such experiments were conducted under pH conditions of 1.5 and 4.0.…”

Section: ϫ3mentioning

confidence: 99%

Nanoparticle halos: A new colloid stabilization mechanism

Tohver

Smay

Braem

et al. 2001

Proc. Natl. Acad. Sci. U.S.A.

229

247

View full text Add to dashboard Cite

A new mechanism for regulating the stability of colloidal particles has been discovered. Negligibly charged colloidal microspheres, which flocculate when suspended alone in aqueous solution, undergo a remarkable stabilizing transition upon the addition of a critical volume fraction of highly charged nanoparticle species. Zeta potential analysis revealed that these microspheres exhibited an effective charge buildup in the presence of such species. Scanning angle reflectometry measurements indicated, however, that these nanoparticle species did not adsorb on the microspheres under the experimental conditions of interest. It is therefore proposed that highly charged nanoparticles segregate to regions near negligibly charged microspheres because of their repulsive Coulombic interactions in solution. This type of nanoparticle haloing provides a previously unreported method for tailoring the behavior of complex fluids. Colloidal suspensions enjoy widespread use in applications ranging from advanced materials to drug delivery. By tailoring interactions between colloidal particles, one can design stable fluids, gels, or colloidal crystals needed for ceramics processing (1), coating (2), direct write (3), photonic (4-9), and pharmaceutical (10, 11) applications. Long range, attractive van der Waals forces are ubiquitous and must be balanced by Coulombic, steric, or other repulsive interactions to engineer the desired degree of colloidal stability.The self-organization of highly charged nanoparticles and their influence on the behavior of complex fluids in which they dwell has received scant attention. The traditional view is that small particles or other species (e.g., polyelectrolyte, polymer, or micelles) in solution can promote flocculation of stable colloidal suspensions via an entropic depletion interaction (12-15). The term ''depletion'' describes the exclusion of these smaller species from the gap region between colloidal particles that arises when their separation distance becomes less than the characteristic depletant size. The resulting concentration gradient between the gap region and bulk solution gives rise to an attractive force, whose magnitude scales with the volume fraction of smaller species, their charge, and the size ratio of large to small species (12,15,16). However, emerging theoretical work (17-19) suggests that charged species in solution may affect system stability through other self-organizing pathways. For example, charged nanoparticles have been predicted to segregate to regions surrounding large uncharged colloids, especially in systems with high size asymmetry and many more small to large spheres (18). This segregation is driven solely by a Coulombic repulsion between smaller species in solution and occurs simply because the larger particles represent a big volume without charge. The key question we wish to explore is whether this type of haloing process can provide a mechanism for stabilizing colloidal species.Here, we study the effects of highly charged nanoparticles on the behavior of ne...

show abstract

“…(1) too small to cause depletion flocculation. Generally speaking a reduction in solvent quality reduces the depletion interaction potential [24][25][26][27][28][29].…”

Section: Introductionmentioning

confidence: 99%