Interactions in colloidal mixtures: Partial structure factors in mixtures of colloidal silica and an anionic oil-in-water microemulsion

Steven R. Kline; Eric W. Kaler

doi:10.1006/jcis.1998.5543

Interactions in colloidal mixtures: Partial structure factors in mixtures of colloidal silica and an anionic oil-in-water microemulsion

Steven R. Kline, Eric W. Kaler

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Abstract

We have investigated the colloidal stability and interactions in a mixture of colloidal silica (Ludox(TM)) and an oil-in-water microemulsion (AOT/decane/brine). Stable silica-microemulsion mixtures containing large fractions of dispersed phase (φ(oil) + φ(Ludox) > 0.36) can be prepared. For fixed silica and AOT concentrations, the addition of decane increases the size of the microemulsion droplets. Since the surfactant concentration remains constant, this droplet growth is balanced by a decrease in the number density of droplets. Partial structure factors for the mixture are extracted from sets of small-angle neutron scattering (SANS) data using a solvent contrast variation technique. The extracted partial structure factors are compared qualitatively to model calculations for a multicomponent sticky hard sphere (SHS) fluid. A shallow contact potential (approximately 2.6 kT) between the Ludox particles is necessary to obtain agreement between model and experiment in the low-q region of the partial structure factors. The magnitude of this contact potential does not change with decane concentration, in agreement with the macroscopic observation that there is no observable change in the stability of these silica-microemulsion mixtures.

Original language	English (US)
Pages (from-to)	392-401
Number of pages	10
Journal	Journal of Colloid And Interface Science
Volume	203
Issue number	2
DOIs	https://doi.org/10.1006/jcis.1998.5543
State	Published - Jul 15 1998

Bibliographical note

Funding Information:
This work was supported by E. I. duPont de Nemours & Co. The authors thank R. D. Koehler for many useful discussions, C. Glinka and J. Barker (NIST) for their assistance with the SANS measurements, and V. Garmus for helpful suggestions. This work is also based upon activities supported by the National Science Foundation under Agreement No. DMR-9423101. Certain trade names and company products are identified to adequately specify the experimental procedure. In no case does such identification imply recommendation or endorsement by the National Institute of Standards and Technology, nor does it imply that the products are necessarily the best for the purpose.

Keywords

Bimodal suspensions
Contrast variation
Microemulsions
Small angle scattering
Structure factor

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title = "Interactions in colloidal mixtures: Partial structure factors in mixtures of colloidal silica and an anionic oil-in-water microemulsion",

abstract = "We have investigated the colloidal stability and interactions in a mixture of colloidal silica (Ludox(TM)) and an oil-in-water microemulsion (AOT/decane/brine). Stable silica-microemulsion mixtures containing large fractions of dispersed phase (φ(oil) + φ(Ludox) > 0.36) can be prepared. For fixed silica and AOT concentrations, the addition of decane increases the size of the microemulsion droplets. Since the surfactant concentration remains constant, this droplet growth is balanced by a decrease in the number density of droplets. Partial structure factors for the mixture are extracted from sets of small-angle neutron scattering (SANS) data using a solvent contrast variation technique. The extracted partial structure factors are compared qualitatively to model calculations for a multicomponent sticky hard sphere (SHS) fluid. A shallow contact potential (approximately 2.6 kT) between the Ludox particles is necessary to obtain agreement between model and experiment in the low-q region of the partial structure factors. The magnitude of this contact potential does not change with decane concentration, in agreement with the macroscopic observation that there is no observable change in the stability of these silica-microemulsion mixtures.",

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note = "Funding Information: This work was supported by E. I. duPont de Nemours & Co. The authors thank R. D. Koehler for many useful discussions, C. Glinka and J. Barker (NIST) for their assistance with the SANS measurements, and V. Garmus for helpful suggestions. This work is also based upon activities supported by the National Science Foundation under Agreement No. DMR-9423101. Certain trade names and company products are identified to adequately specify the experimental procedure. In no case does such identification imply recommendation or endorsement by the National Institute of Standards and Technology, nor does it imply that the products are necessarily the best for the purpose.",

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N2 - We have investigated the colloidal stability and interactions in a mixture of colloidal silica (Ludox(TM)) and an oil-in-water microemulsion (AOT/decane/brine). Stable silica-microemulsion mixtures containing large fractions of dispersed phase (φ(oil) + φ(Ludox) > 0.36) can be prepared. For fixed silica and AOT concentrations, the addition of decane increases the size of the microemulsion droplets. Since the surfactant concentration remains constant, this droplet growth is balanced by a decrease in the number density of droplets. Partial structure factors for the mixture are extracted from sets of small-angle neutron scattering (SANS) data using a solvent contrast variation technique. The extracted partial structure factors are compared qualitatively to model calculations for a multicomponent sticky hard sphere (SHS) fluid. A shallow contact potential (approximately 2.6 kT) between the Ludox particles is necessary to obtain agreement between model and experiment in the low-q region of the partial structure factors. The magnitude of this contact potential does not change with decane concentration, in agreement with the macroscopic observation that there is no observable change in the stability of these silica-microemulsion mixtures.

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Interactions in colloidal mixtures: Partial structure factors in mixtures of colloidal silica and an anionic oil-in-water microemulsion

Abstract

Bibliographical note

Keywords

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