Fluorescence Microscopy Imaging of Giant Folding in a Catanionic Monolayer

Coppock, Joseph D.; Krishan, Kapilanjan; Dennin, Michael; Moore, Brian G.

doi:10.1021/la803773y

Cited by 15 publications

(24 citation statements)

References 29 publications

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“…Furthermore, the plateau surface pressure beyond film collapse also indicates a stable, difficult to remove interfacial layer, which could promote the irreversible adsorption at the interface. This behavior of Citrem is particularly interesting because some of the more commonly used emulsifiers, such as SDS, were unable to make compressible monolayers at the air–water interface in the Langmuir trough because of its high solubility in the aqueous phase. , Researchers also showed that SDS desorbed from the air–water interface when its concentration in the aqueous phase decreased . Thus, irreversible adsorption of Citrem at the interface was critical in preventing its desorption from the interface when the cream layer after centrifugation was redispersed in DI water.…”

Section: Resultsmentioning

confidence: 99%

Conversion of Viscous Oil-in-Water Nanoemulsions to Viscoelastic Gels upon Removal of Excess Ionic Emulsifier

Kadiya

Ghosh

2019

Langmuir

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Viscous, flowable nanoemulsions stabilized with ionic emulsifier can be transformed into repulsively jammed elastic gels that do not flow under gravity by reducing the droplet size and increasing the interfacial repulsive shell layer thickness. However, a high concentration of emulsifier required to achieve nanodroplets could remain in the continuous phase and lead to oscillatory structural forces, thereby reducing repulsive interaction and forming flowable liquid systems. It was hypothesized that the removal of excess emulsifier from a nanoemulsion could lead to the formation of repulsive gels. Canola oil-in-water nanoemulsions, containing 40 wt % oil, were prepared with a citric acid ester of monoglyceride (Citrem) using a high-pressure homogenizer. The excess emulsifier in the aqueous phase was removed by multiple ultracentrifugation cycles, and the droplet size, rheology, and stability of the nanoemulsions were investigated as a function of excess Citrem concentration. Nanoemulsions with average droplet sizes of 222 and 150 nm were obtained with 3 and 5 wt % Citrem, respectively. The removal of excess Citrem did not change the droplet size significantly. However, the viscosity, yield stress, and storage moduli increased significantly with the reduction of excess Citrem and the decrease in droplet size, converting the flowable weak gel nanoemulsion to a strong viscoelastic gel. The calculated values of oscillatory structural forces decreased with the removal of excess emulsifier, leading to an increase in repulsive interactions and the thickness of the electric double layer. Such an increase in interdroplet separation led to an increase in the effective oil volume fraction beyond the maximum random jamming of oil droplets and the formation of a viscoelastic nanoemulsion gel.

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Section: Resultsmentioning

confidence: 99%

Conversion of Viscous Oil-in-Water Nanoemulsions to Viscoelastic Gels upon Removal of Excess Ionic Emulsifier

Kadiya

Ghosh

2019

Langmuir

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“…However, when monolayer is composed of both positive and negative head groups, so called catanionic monolayer, the fold occurs 33,38,39 Fig. 5 .…”

Section: Topography Of Collapsementioning

confidence: 99%

Collapsed States of Langmuir Monolayers

2016

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“…mixtures of cationic and anionic surfactants. 11,12 Generally speaking, such mixtures are expected to show good properties with respect to foam formation and stabilisation for three principal reasons: (i) catanionic mixtures are known to pack very efficiently at the gas/water interface, [12][13][14][15][16][17] rendering the interfaces themselves strongly viscoelastic; 13,14,[18][19][20][21][22][23] (ii) the critical micelle (or aggregation) concentration, although generally low in these strongly non-ideal mixtures, has a finite value which provides free surfactant in solution 24 and (iii) these mixtures form vesicles 25 usually considered at thermodynamic equilibrium. 26 The presence of vesicles provides bulk viscoelastic properties (ref.…”

Section: Introductionmentioning

confidence: 99%