Evaluating the Dispersant Stabilization of Colloidal Suspensions from the Scaling Behavior of Gel Rheology and Adsorption Measurements

Abstract

Maintaining suspension stability by effective particle dispersion in systems with attractive interactions can be accomplished by the addition of dispersants that modify the interparticle potential to provide steric or electrostatic barriers against aggregation. The efficacy of such dispersants is typically considered simply by the modification of suspension rheological properties as a function of the overall added dispersant concentration. However, such considerations do little to reveal the molecular origin of differences in dispersant efficacy because they do not consider differences in surface activity. We combine measured adsorption isotherms with the rheological characterization of the elasticity of colloidal gels formed by particle aggregation to provide a more meaningful assessment of dispersant efficacy. The rheological data show that the dispersants are effective at reducing particle aggregation, whereas, from the adsorption isotherms, they differ considerably in their surface coverage at constant overall concentration. When compared at constant dispersant particle surface coverage, the gel rheology shows marked differences across the different dispersants, as opposed to comparisons at constant overall dispersant concentration in the suspensions. In particular, the power-law volume fraction scaling of gel elasticity at constant coverage reveals clear differences in the critical volume fraction for gel formation for the different dispersants. The most efficacious dispersant is that associated with the largest critical volume fraction for gel formation at a given surface coverage. This work demonstrates the utility of rheological investigations coupled with accurate determinations of surface coverage to better differentiate dispersant performance, which may improve efforts to engineer new dispersant molecules.

Micellization and Adsorption to Carbon Black of Polyisobutylene‐Based Ionic Liquids

“…These absorbances provide an effective method to monitor dispersant concentration, and they arise from the aromatic chromophore present in the (3‐bromopropoxy)phenyl moiety and/or the aromatic cation associated with the IL moiety itself (e.g., ISO). Other methods that have been used to quantify the remaining PIB dispersant concentration include fluorescence, infrared spectroscopy, and pH indicators; however, UV–vis provides for simple and quantitative characterization.…”

“…Polyisobutylene (PIB) has found widespread use as an additive in lubricating oils for internal combustion engines, specifically as a dispersant, due to its advantageous properties including a low glass transition temperature ( T g ), chemical, oxidative, and thermal stability, and ease of chemical modification . PIB succinimide (PIBSI) is a commercially produced PIB‐based dispersant commonly used in lubricating oils to maintain solubility of polyaromatic hydrocarbons (PAHs) (i.e., soot), which are produced from incomplete combustion of fuel and are carried into the lubricating oil when exhaust gases pass the piston rings .…”

Molecular Engineering of Superplasticizers for Metakaolin‐Portland Cement Blends with Hierarchical Machine Learning

“…[50] The introduction of metakaolin, which is believed to retain much of its intrinsic clay structure, lends further complexity due to its heterogeneous surface charge density and pH-dependent flocculation and adsorption behaviors. Addressing these issues may require parametrization of the system chemistry to resolve contributions from particle-particle interactions in the percolating network that comprises paste from solution-mediated effects due to changes in viscosity and polymer adsorption, [51] but this would provide a broader understanding of the forces that drive the rheological properties of MK-PC paste.…”

Role of Low Molecular Weight Polymers on the Dynamics of Silicon Anodes During Casting

“…Although low molecular weight dispersants are often included in ceramics processing, this approach has not been widely applied to battery materials. In the processing of oxide‐based powders, such as, barium titanate, silica, alumina, mullite, yttria stabilized zirconia ceramics, a small amount (less than 1 wt %) of a low molecular weight polymer or small molecule, such as citric acid, is often added to a slurry to prevent flocculating, separating, and control flow behavior [8–16] . Dispersants function by steric stabilization which occurs when the dispersant adsorbs onto the particle, creating a repulsive force that physically separates the particles [17–19] …”