Solubilizable dispersions

Solubilizable Dispersions (19). The chemistry of solubilizable acrylic dispersions is a hybrid of emulsion and water-reducible technology. These polymers are synthesized by emulsion techniques but contain acidic or basic functionality that renders them water soluble upon neutralization with an appropriate titrant. For example, if the solubilizing functionality is acidic, the polymer will behave like an emulsion below a certain critical pH range, like a highly swollen emulsion within the critical pH range, and like a true water-soluble polymer at sufficiently high pH values. Such polymers offer a favorable balance of properties for many coating applications. 

Property Aqueous Dispersion Solubilizable Dispersion Water Reducible... 

Nanoparticles solubilized in w/o microemulsions have been obtained by performing in situ suitable reactions [196], by dispersion of particles [219,220], or by controlled nanoprecipitation of a solubilizate [221,222]. 

Another method is based on the evaporation of a w/o microemulsion carrying a water-soluble solubilizate inside the micellar core [221,222], The contemporaneous evaporation of the volatile components (water and organic solvent) leads to an increase in the concentration of micelles and of the solubilizate in the micellar core. Above a threshold value of the solubilizate concentration, it starts to crystallize in confined space. Nanoparticle coalescence could be hindered by surfactant adsorption and nanoparticle dispersion within the surfactant matrix. 

Solutions of surfactant-stabilized nanogels share both the advantage of gels (drastic reduction of molecular diffusion and of internal dynamics of solubilizates entrapped in the micellar aggregates) and of nonviscous liquids (nanogel-containing reversed micelles diffuse and are dispersed in a macroscopicaUy nonviscous medium). Effects on the lifetime of excited species and on the catalytic activity and stability of immobilized enzymes can be expected. 

Solubilizate 1 Solubilizate 2 1 Oily dispersion 1 Oily dispersion 2 3 Crystalline... 

FIGURE 5.8 Bioavailability of 60-mg CoQio single dosing (early absorption). AUCo 4 h (pmol/mmol x h) after a single dose of 60-mg CoQiq. Data are expressed as mean SD. Differences between formulations were tested with ANOVA and post hoc test Student-Newman-Keuls test. p < 0.05 (both solubilizates vs oily dispersion 1 and oily dispersion 2 vs crystalline) p < 0.01 (both solubilizates vs crystalline). 

Solubilization is distinguished from emulsification (the dispersion of one liquid phase in another) by the fact that in solubilization, the solubilized material (the solubilizate ) is in the same phase as the solubilizing solution and the system is consequently thermodynamically stable. 

It is logical to ask what may happen if the dispersed solubilizate phase (water or oil) is added to the water-oil-surfactant system to such a high extent that the core of the micelle cannot contain it any more. The answer is that at the initial stage of such extra addition the result will be a microemulsion coexisting with some excess solubilizate phase (e.g. W/O with excess W). When with further addition the ratio between the continuous and dispersed phases comes to, say, about 1 1, the two commonly form an intermediate microemulsion phase between the OAV and W/O types within a specific range of temperatures this is known as bicontinuous microemulsion . With further addition of the dispersed phase, there can be an inversion from one type to the other. We shall discuss below these points in more detail from a historical viewpoint. 

The term solubilization was coined by McBain [152] to denote the increased solubility of a given compound, associated with the presence of surfactant micelles or inverted micelles in the solution. The most popular solubilization process is the transfer of oil molecules into the core of surfactant micelles. Thus, oil that has no solubility (or limited solubility) in the aqueous phase becomes water soluble in the form of solubilizate inside the micelles. This process has a central importance for washing of oily deposits from solid surfaces and porous media, and for removal of oily contaminants dispersed in water. The great practical importance of solubilization is related to its application in the everyday life in the personal care and household detergency, as well as in various industrial processes [153]. 

III two phases, the first an aqueous solution containing mono-molecularly dispersed surfactant, the second rich in surfactant with a small amount of water and the solubilizate dissolved in it ... 

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