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Biomedical subjects

EW Kaler

Publications and source records attributed to EW Kaler.

4 recordsLinked to original sources
PubMed2000

A class of microstructured particles through colloidal crystallization

Microstructured particles were synthesized by growing colloidal crystals in aqueous droplets suspended on fluorinated oil. The droplets template highly ordered and smooth particle assemblies, which diffract light and have remarkable structural stability. The method allows control of particle size and shape from spheres through ellipsoids to toroids by varying the droplet composition. Cocrystallization in colloidal mixtures yields anisotropic particles of organic and inorganic materials that can, for example, be oriented and turned over by magnetic fields. The results open the way to controllable formation of a wide variety of microstructures.

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PubMed1999

The Effect of Anomeric Head Groups, Surfactant Hydrophilicity, and Electrolytes on n-Alkyl Monoglucoside Microemulsions.

The effects of the variables of head group structure and salt concentration on microemulsions formed in mixtures of water, alkyl ethylene glycol ethers (CkOC2OCk), and n-alkyl beta-d-glucopyranosides (CmbetaG1) are explored. Phase behavior of mixtures containing an anomer of the surfactant (n-alkyl alpha-d-glucopyranoside, CmalphaG1), or surfactants with long head groups (n-alkyl maltopyranosides, CmG2), or NaCl or NaClO4 as electrolyte are systematically reported as a function of temperature and composition. The substitution of n-alkyl alpha-d-glucopyranosides for n-alkyl beta-d-glucopyranosides causes precipitation under some conditions in all mixtures studied. These solubility boundaries begin in the water-surfactant binary mixture at the Krafft boundary, then extend to high concentrations of both surfactant and oil. Increasing the effective length of the surfactant head group by adding CmG2 to water-CkOC2OCk-CmbetaG1 mixtures moves the phase behavior dramatically up in temperature when even small amounts of CmG2 are used. Adding a lyotropic electrolyte, NaCl, to water-CkOC2OCk-CmbetaG1 mixtures moves the phase behavior down in temperature, while the hydrotropic electrolyte NaClO4 moves the phase behavior up in temperature. Copyright 1999 Academic Press.

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PubMed1998

Interactions in Colloidal Mixtures: Partial Structure Factors in Mixtures of Colloidal Silica and an Anionic Oil-in-Water Microemulsion.

We have investigated the colloidal stability and interactions in a mixture of colloidal silica (LudoxTM) and an oil-in-water microemulsion (AOT/decane/brine). Stable silica-microemulsion mixtures containing large fractions of dispersed phase (phioil + phiLudox > 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. Copyright 1998 Academic Press.

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