Potassium, Calcium, and Magnesium Bridging of AOT to Mica at Constant Ionic Strength

Allen, Finian J.; Truscott, Christopher; Gutfreund, Philipp; Welbourn, Rebecca J. L.; Clarke, Stuart M.

doi:10.1021/acs.langmuir.9b00533

Cited by 18 publications

(10 citation statements)

References 41 publications

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“…Interestingly, in addition to these studies, there are also studies that report favorable interactions between like-charged systems even in the presence of monovalent counterions. For example, anionic surfactants adsorb at negatively charged mica in the presence of Cs + (ref ) and K + (ref ) counterions. These interactions, while not identified or quantified specifically, appear to be equivalent to bridging interactions.…”

Section: Introductionmentioning

confidence: 99%

Quantification of Mono- and Multivalent Counterion-Mediated Bridging in Polyelectrolyte Brushes

2021

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Multivalent counterion-induced bridging interactions have been identified as the key mechanism of drastic collapse of the height of polyelectrolyte (PE) brushes. In this article, we employ all-atom molecular dynamics simulations to quantify the bridging interactions in PE brushes for counterions of different sizes and valences. We identify that unlike the current notion, bridging interactions are not the sole function of the counterion valence. Rather the bridging interactions depend on the fraction of counterions (of a given type) that get physically condensed on the PE backbone as well as the size of the counterion solvation shell. These mechanisms ensure that certain monovalent counterions demonstrate much stronger bridging interactions than those witnessed for certain divalent and trivalent counterions, while certain counterions of identical valences show drastically different bridging interactions. We argue that these counterion-specific bridging interactions eventually enable not only the significant reduction of the PE brush height in the presence of certain multivalent screening counterions but may also give rise to scenarios where the brush height reduction for certain monovalent counterions is larger than that observed for certain divalent and trivalent counterions. The latter observation contradicts the experimental findings where the multivalent counterions invariably led to a larger decrease in the height of the PE brushes; we argue that this discrepancy stems from the fact that in our simulations we only consider densely grafted and short (and hence less flexible) PE brushes that hinder the formation of different laterally inhomogeneous structures (such as pinned micelles and cylindrical bundles) that would have led to a larger brush height reduction (in experiments, which invariably consider longer and less densely grafted brushes, the formation of such inhomogeneous structures is primarily responsible for the larger brush height reduction in the presence of multivalent counterions). Finally, we also probe the dynamic properties of the counterions (i.e., their time-dependent displacements) and their bridging interactions (i.e., lifetime of bridging interactions).

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Section: Introductionmentioning

confidence: 99%

Quantification of Mono- and Multivalent Counterion-Mediated Bridging in Polyelectrolyte Brushes

2021

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“…Second, ion bridging interactions have established roles in the surface alteration of relatively insoluble minerals such as apatite, silica, and mica. [ 26 ] Assuming a central role of Ca 2+ ion mediated bridging interactions for carbonates, the adsorbed contents of the organic acid are expected to positively corelate with the added Ca 2+ ion content and then saturate. Instead, increasing Ca 2+ ion contents during organic acid‐crystal contact produced substantial reductions in the bound organic fractions (Figure 2e).…”

Section: Resultsmentioning

confidence: 99%

Nonmonotonic Coupled Dissolution‐Precipitation Reactions at the Mineral–Water Interface

Rao

Ayirala

Alotaibi

et al. 2021

Adv Funct Materials

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Dissolution is inherent to fluid‐mineral systems. Yet its impact on minerals reacting with electrolytes is overlooked. Here, a novel nonmonotonic behavior for the surface interactions of carbonates (calcite and Mg‐calcite) with organic acids is reported. Applying a bioinspired approach, Mg‐calcite sensors via amorphous precursors, avoiding any preconditioning with functional groups are synthesized. A quartz crystal microbalance is used to study the mass changes of the mineral on contact with organic acids under varying ionic conditions, temperatures, and flow velocities. Supported by confocal Raman microscopy and potentiometric titrations, nonmonotonous mass developments are found as a function of Ca2+ concentration and flowrate, and attributed to three coupled chemical reactions: i) carbonate dissolution via Ca2+ ion complexation with organic molecules, and the formation of organo‐calcium compounds as ii) a surface phase at the mineral–water interface, and iii) particles in the bulk fluid. These processes depend on local ion contents and the precipitation onset (i.e., saturation index) of organo‐calcium salts, both of which substantially differ in the bulk fluid and in the fluid boundary layer at mineral interfaces. This continuum between dissolution and precipitation provides a conceptual framework to address reactions at mineral interfacial across disciplines including biomineralization, ocean acidification and reservoir geochemistry.

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“…The surface and surfactant ion do not need to be of opposite charge for adsorption to occur. Different counterions, especially divalent ions, can induce adsorption between like charged surfactants and surface, as shown by the strong adsorption of the negative surfactant ion of Aerosol OT on the negative surfaces of both silica and mica , when divalent ions are present. Zwitterionic surfactants, which usually contain a more or less closely spaced pair of opposite charges, can also adsorb on a charged surface.…”

Section: Introductionmentioning

confidence: 99%

Unusual Maximum in the Adsorption of Aqueous Surfactant Mixtures: Neutron Reflectometry of Mixtures of Zwitterionic and Ionic Surfactants at the Silica–Aqueous Interface

Ma¹,

Li²,

Thomas³

et al. 2021

Langmuir

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The adsorption of two zwitterionic surfactants, dodecyldimethylammonium propanesulfonate (C12PS) and dodecyldimethylammonium carboxybetaine (C12CB), and of their mixtures with the cationic dodecyltrimethylammonium bromide (C12TAB) and the anionic sodium dodecylsulfate (SDS) at the silica–water interface has been studied by neutron reflection (NR). The total adsorption, the composition of the adsorbed layer, and some structural information have been obtained over a range of concentrations from below the critical micelle concentration (CMC) to about 30× the mixed CMC. The adsorption behavior has been considered in relation to the previously measured micellar equilibrium of these mixtures in their bulk solutions and their adsorption at the air–water interface. C12CB adsorbs cooperatively close to its CMC to form an almost complete bilayer on its own, whereas C12PS adsorbs more weakly in a fragmented bilayer structure. Although SDS does not normally adsorb at the silica–water interface, SDS adsorbs strongly and cooperatively with C12PS at fractional SDS compositions up to about 0.5. This cooperativity is lost when the adsorbed fraction of SDS rises above about 0.5. At this point, adsorption drops sharply, creating an unusual maximum in the variation of adsorption with a total concentration above the mixed CMC. Neither the increase in cooperativity nor the subsequent decline in adsorption results directly from variations of the independently determined monomer concentrations in the bulk solution. The adsorption maximum is predominantly the effect of strong cooperative interaction, possibly accompanied by partial segregation of SDS within the layer, followed by charge repulsion from the surface. Although the solution aggregation and adsorption at the A–W interface are similar for SDS with C12CB, the addition of SDS to C12CB at the silica–water interface promotes the opposite behavior to that of SDS with C12PS, and SDS simply disrupts the cooperative binding of C12CB. Unlike SDS, the cationic surfactant C12TAB adsorbs on silica. It therefore coadsorbs at the SiO2–W interface with either C12CB or C12PS. However, in neither case is there any pronounced cooperativity and, even though the presence of C12TAB might be expected to favor adsorption, the adsorption is generally unexpectedly low.

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Potassium, Calcium, and Magnesium Bridging of AOT to Mica at Constant Ionic Strength

Cited by 18 publications

References 41 publications

Quantification of Mono- and Multivalent Counterion-Mediated Bridging in Polyelectrolyte Brushes

Quantification of Mono- and Multivalent Counterion-Mediated Bridging in Polyelectrolyte Brushes

Nonmonotonic Coupled Dissolution‐Precipitation Reactions at the Mineral–Water Interface

Unusual Maximum in the Adsorption of Aqueous Surfactant Mixtures: Neutron Reflectometry of Mixtures of Zwitterionic and Ionic Surfactants at the Silica–Aqueous Interface

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