On the stability of nanoparticles coated with polyelectrolytes in high salinity solutions

Abstract

ABSTRACT:We have developed and applied a molecular theory that enables the investigation of the interactions between polyelectrolyte coated nanoparticles (NPs) in aqueous solutions. Potential applications of polyelectrolyte-coated NPs involve nanosensors for oil well characterization. To account for the high salinity environment encountered in an oil well or brine solution, we also considered in the theoretical description counterion condensation as well as ion-ion paring. We identified the design criteria to achieve dispersion stability of NPs coated with either polyacrylic acid (pAA), poly acrylamido-2-methylpropane sulfonate (pAMPS), or an alternating copolymer of acrylic acid and acrylamido-2-methylpropane sulfonate (pAA-a-AMPS) under brine-like conditions and quantified the effects of NP core size, molecular weight, density of the polyelectrolyte coating, and polymer chemistry. The results were summarized in stability diagrams, which predict the polymer surface coverage and molecular weight that is required for the NP solution to remain dispersed.

High temperature stability and low adsorption of sub-100 nm magnetite nanoparticles grafted with sulfonated copolymers on Berea sandstone in high salinity brine

“…In API brine, the charges on the polyelectrolyte layer are screened and steric repulsion becomes dominant stabilization mechanism, with a small degree of electrosteric repulsion. Factors such as the size of IONPs, molecular weight of polymers, composition of polymers, and pH also affect the stability of NPs [25,54]. The smaller size of the nanoparticles, versus the 150 to 200 nm NPs reported previously [34] favors greater steric stabilization relative to the VDW attractive forces.…”

Theoretical Modeling of Chemical Equilibrium in Weak Polyelectrolyte Layers on Curved Nanosystems

“…In another work, MT was used to predict and rationalize experimental results on the stability of citric acid-coated/PEGylated iron oxide NPs under different pH and ionic strength conditions [ 92 ]. More recently, MT calculations provided the design criteria to achieve dispersion stability of NPs coated with polyacrylic acid (pAA), poly acrylamido-2-methylpropane sulfonate (pAMPS), or an alternating copolymer of the two (pAA-a-AMPS) under brine-like conditions (high pH and salinity of the solution) [ 93 ]. The authors explored the effects of surface density ( Figure 3 , panel A), NP core size ( Figure 3 , panel B), solution’s salt concentration, and pH ( Figure 3 , panels C and D, respectively).…”

“…Starting again with the example of carboxylic acid binding to Na ions in solution, the chemical reaction can be described as and characterized by a chemical equilibrium constant and an extent of the reaction (or fraction of bound monomer) in analogy to and . MT calculations were used to study sodium ion binding to NP coated with polyelectrolytes in high salinity solutions [ 93 ]. As mentioned above, the authors focused on exploring the conditions that would render stable solution of NP modified with either polyacrylic acid (pAA), poly acrylamido-2-methylpropane sulfonate (pAMPS), or an alternating copolymer of the two [ 93 ].…”

“…MT calculations were used to study sodium ion binding to NP coated with polyelectrolytes in high salinity solutions [ 93 ]. As mentioned above, the authors focused on exploring the conditions that would render stable solution of NP modified with either polyacrylic acid (pAA), poly acrylamido-2-methylpropane sulfonate (pAMPS), or an alternating copolymer of the two [ 93 ].…”

“…( D ) Barrier height versus pH for various salt concentrations. Conditions as in panel C. (Reprinted with permission from the authors of [ 93 ]. Copyright 2014 Wiley Periodicals, Inc.).…”