Interaction particle-surfactant

Photon correlation spectroscopy was used to study the effects of a series of nonionic surfactants on the Stokes radius (R) of low density lipoprotein (LDL2) particles (Jl, 32). LDL2 interacted with surfactants in a manner similar to membranes. 

Recent investigations have shown that the behavior and interactions of surfactants in a polyvinyl acetate latex are quite different and complex compared to that in a polystyrene latex (1, 2). Surfactant adsorption at the fairly polar vinyl acetate latex surface is generally weak (3,4) and at times shows a complex adsorption isotherm (2). Earlier work (5,6) has also shown that anionic surfactants adsorb on polyvinyl acetate, then slowly penetrate into the particle leading to the formation of a poly-electroyte type solubilized polymer-surfactant complex. Such a solubilization process is generally accompanied by an increase in viscosity. The first objective of this work is to better under-stand the effects of type and structure of surfactants on the solubilization phenomena in vinyl acetate and vinyl acetate-butyl acrylate copolymer latexes. 

By using modified colloidal particles as templates, silicon oxide macroporous materials with uniform submicrometer-sized pores can be synthesized.[14] Modified polystyrene emulsion microspheres (200 1000 nm) can be electronegative (sulfates) or electropositive (amidines). After these microspheres are packed in an orderly fashion, they can interact with surfactants and silicon oxides to form macroporous solid composites, and further to form macroporous materials after the removal of the templates by calcination. The sizes of the macropores in the products range from 150 to 1000 nm. Macroporous Ti02 can also be prepared in a similar way. 

Polymer-surfactant interactions are the basis for the rheological behavior of MHAPs. Other surfactant-polymer systems have previously been investigated. One example is the interaction of surfactants with polymers such as poly(ethylene oxide), which results in greater solution viscosities than with the polymer alone (e.g., ref. 25 and references therein). The interaction of surfactants or latexes with hydrophobically modified water-soluble polymers has also been shown to produce unique rheology (2, 5, 26, 27). In these systems, the latex particles or the surfactant micelles serve as reversible cross-link points with a hydrophobic region of a polymer molecule in dynamic association with a latex particle or surfactant micelle (27). 

Depending on the particle-surfactant system, one or more of the above contributions can be responsible for adsorption. The dominating one would depend on the nature and concentration of the surfactant, the surface chemistry of the particle, and solution properties such as pH and ionic strength. Electrostatic and lateral interaction forces are usually the major factors determining the adsorption of surfactants on oxides and other non-metallic minerals. Chemical interactions become more dominant for surfactant adsorption on salt-type minerals, such as carbonates and sulfides. 

For controlling interdroplet interactions, co-surfactants (alcohols of different chain lengths) were added into the system. The effective particle diameter of hydrated titania was found to decrease monotonically with increase in the chain length of the alcohol (butanol to octanol) irrespective of the water/surfactant molar ratio (10 or 20). It was also shown that with a systematic increase in the ratio [octanol]/[Ti(AOT)4], i.e. 0.2-1.0, the effective diameter of hydrated titania decreased monotonically. Finally, the particle size was found to increase with the concentration of Ti(AOT)4. 

Interactions between soluble polymer and either colloidal particles, surfactant micelles, or proteins control the behavior and viability of a large number of chemical and biochemical products and processes. Considerable scientific interest also centers on these interactions because of their profound and, sometimes, unexpected effects on the thermodynamics and dynamics of the dispersions or solutions, known collectively as complex fluids. Syntheses of novel block copolymers, improved scattering and optical techniques for characterization, and predictions emerging from sophisticated statistical mechanical approaches provide additional stimulus. Thus, the area is vigorous academically and industrially as evidenced by the broad and international participation in this volume. 

K. Esumi, Interactions between surfactants and particles dispersion, surface modification and adsolubihzation, J. Colloid Interf. Sci. 2001, 241,1-17. 

Mesomorphic Phase. A phase consisting of anisometric molecules or particles that are aligned in one or two directions but randomly arranged in other directions. Such a phase is also commonly referred to as a liquid-crystalline phase or simply a liquid crystal. The mesomorphic phase is in the nematic state if the molecules are oriented in one direction, and in the smectic state if oriented in two directions. Mesomorphic phases are also sometimes distinguished on the basis of whether their physical properties are mostly determined by interactions with surfactant and solvent (lyotropic liquid crystals) or by temperature (thermotropic Uquid crystals). See also Neat Soap. 

Dr. Zelenev s professional interests include industrial applications of colloid and surface science, pulp and paper, oil and gas production, coagulation and flocculation, lyophobic and lyophilic colloidal systems, surfactant phase behavior, interaction of surfactants with surfaces, microencapsulation, particle deposition and aggregation, particle and surfactant transport in porous media, wetting and spreading, development of novel experimental methods for studying colloidal systems, and physical-chemical mechanics. Dr. Zelenev is an inventor on four issued U.S. patents and five pending patent applications, coauthor of 22 scientific publications, and coauthor of the textbook Colloid and Surface Chemistry (Elsevier, 2001). 

In the area of paint and coatings complex interactions between surfactants, polymers, and latex particles play an important role. In most formulations, a mixture of several surfactants is used. Alkylphenol ethoxylates are tradi-... 

Adsorption experiments conducted with PEO and alumina particles showed no adsorption of the former on the particles. Because it is known that SDS adsorbs on alumina and that PEO interacts with SDS, PEO adsorption tests were repeated with alumina pretreated with SDS. The authors observed that the presence of a surfactant on the alumina surface caused near-complete adsorption of the polymer as a consequence of its interaction with surfactant aggregates. This result showed that it was possible to force the adsorption of a polymer on a solid surface on which it spontaneously does not adsorb. Instead of drastically modifying the solid-surface properties to force the adsorption of PEO, it seems, by far, more convenient to form surfactant aggregates at the solid-liquid interface and then to allow the polymer to adsorb. 

The gap between two colliding particles (bubbles, droplets, solid particles, surfactant micelles) in a colloidal dispersion can be treated as a film of uneven thickness. Then, it is possible to utilize the theory of thin films to calculate the energy of interaction between two colloidal particles. Deijaguin [276] has derived an approximate formula which expresses the energy of interaction between two spherical particles of radii and i 2 through integral of the excess surface free energy per unit area, f h), of a plane-parallel film of thickness h [see Eq. (161)] ... 

Specific interactions between surfactant ions and other additives in the system will sometimes significantly alter the behaviour of the particles. Starch and related materials even in concentrations as low as several parts per million can affect the adsorption of sodium oleate and other fatty acids on to minerals such as calcite... 

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