Mono- and Di-valent Salts as Modifiers of PEO-PPO-PEO Block Copolymer Interactions with Silica Nanoparticles in Aqueous Dispersions

Abstract

Colloidal stabilization of nanoparticle dispersions is central to applications including coatings, mineral extraction, and dispersion of oil spills in oceanic environments, which often involves oil-mineral-aggregates (OMAs). We have an ongoing interest in the modulation of amphiphile micellization and adsorption behavior in aqueous colloidal dispersions in the presence of various additives. Here we evaluate the effect of added salts CaCl 2 , MgCl 2 , and NaCl on the micellization and adsorption behavior of the poly(ethylene oxide)-poly(propylene oxide)-poly(ethylene oxide) triblock copolymer Pluronic P105 (EO 37 PO 56 EO 37 ). In 0.10 wt% silica nanoparticle (10.6 nm average diameter) dispersion, adsorbed block copolymer layer formation begins at a critical surface micelle concentration (csmc) of 0.02 wt%, well below the critical micellization concentration of Pluronic P105 in water. Dye solubilization experiments demonstrate an increase in the csmc upon addition of each salt. Each added salt reaches a level of maximum effectiveness in its ability to disfavor Pluronic P105 adsorption at the silica surface. These peak levels occur at concentrations of 0.005, 0.03, and 0.05 M for CaCl 2 , MgCl 2 , and NaCl, respectively, in the presence of 0.10 wt% silica nanoparticles. We explain these results in the context of an electrostatic displacer mechanism and discuss possible connections to OMA-dispersant formation.

Rhamnolipid Micellization and Adsorption Properties

“…Surfactants play an important role in numerous processes and products for rheological modification [ 4 , 5 ], surface modification [ 6 , 7 ], emulsions [ 8 , 9 ], dispersions [ 10 , 11 ], material synthesis [ 12 , 13 ], drug delivery [ 14 ], etc. Accordingly, biosurfactants have a wide range of potential applications, including detergents in household and agriculture products, solubilizers in pharmaceuticals, wetting and penetrating agents, emulsifiers, dispersants in paints, wetting and thickening agents [ 15 , 16 ].…”

Effect of salt addition on a triblock copolymer-zwitterionic surfactant assembly: insight from excited-state proton transfer

“…[35][36][37] Higher valent salts reduce the CMC or CMT more effectively than the monovalent ones. 38 The binding of the cations with the PEO parts of the pluronic micelles and hydration nature of the ions mainly induced sphere-to-rod shape transitions of the assemblies. The cations bind to the PEO parts directly or via water molecules.…”

Obtaining and Corrosion Performance of Composite Zinc Coatings with Incorporated Carbon Spheres

“…The surfactant molecules may be adsorbed on the CNT surface with their hydrophobic parts next to the surface and the hydrophilic parts facing outward in the solution. Different surfactants may affect the properties of the composite coatings in different ways [14][15][16]. For example, the addition of an anionic surfactant in the depositing bath was found to increase the corrosion resistance of a Ni-CNT composite coating, in contrast to the addition of a cationic surfactant [11].…”