Layering, immiscible components

Emulsification is a stabilizing effect of proteins a lowering of the interfacial tension between immiscible components that allow the formation of a protective layer around oil droplets. The inherent properties of proteins or their molecular conformation, denaturation, aggregation, pH solubility, and susceptibility to divalent cations affect their performance in model and commercial emulsion systems. Emulsion capacity profiles of proteins closely resemble protein solubility curves and thus the factors that influence solubility properties (protein composition and structure, methods and conditions of extraction, processing, and storage) or treatments used to modify protein character also influence emulsifying properties. 

The two designs of the Dean and Stark apparatus (Fig. 2.31(a) and (b) available from Bibby Science Products) carry a flask on the lower cone and a reflux condenser on the upper socket. They are used for the automatic separation of two immiscible components in a distillate and the subsequent return of the upper layer (a) or the lower layer (b) to the reaction flask. 

At concentrations of immiscible components approaching a ratio of 1 1, melts of the cooled and solidified blend materials have morphology like a droplet in a matrix or layers in a matrix depending on the type of components, ratio of their viscosities, and level of interphase interaction. The layered (ribbonlike) distribution is most typical (1). 

However, it is of great interest to understand how the copolymer, which comprises the gel, is spatially distributed in the blend. During the processing it is certainly formed at the interface or interphase between the immiscible components. However, it may be moved away from the interface during subsequent mixing. Instead, it may exist as a layer around the dispersed rubber phase. The copolymer could also exist within the rubber and/or polystyrene phases. 

Arehart SV, Pugh C (1997) Induction of smectic layering in nematic liquid crystals using immiscible components. 1. laterally attached side-chain liquid crystalline poly(norbomene)s and their low molar mass analogs with hydrocarbon/fluorocarbon substituents. J Am Chem Soc 119 3027-3037... 

The theory of the process can best be illustrated by considering the operation, frequently carried out in the laboratory, of extracting an orgaiuc compound from its aqueous solution with an immiscible solvent. We are concerned here with the distribution law or partition law which, states that if to a system of two liquid layers, made up of two immiscible or slightly miscible components, is added a quantity of a third substance soluble in both layers, then the substance distributes itself between the two layers so that the ratio of the concentration in one solvent to the concentration in the second solvent remains constant at constant temperature. It is assumed that the molecular state of the substance is the same in both solvents. If and Cg are the concentrations in the layers A and B, then, at constant temperature ... 

Room temperature ionic liquids are air stable, non-flammable, nonexplosive, immiscible with many Diels-Alder components and adducts, do not evaporate easily and act as support for the catalyst. They are useful solvents, especially for moisture and oxygen-sensitive reactants and products. In addition they are easy to handle, can be used in a large thermal range (typically —40 °C to 200 °C) and can be recovered and reused. This last point is particularly important when ionic liquids are used for catalytic reactions. The reactions are carried out under biphasic conditions and the products can be isolated by decanting the organic layer. 

The two components are immiscible and must be stirred to effect conversion at 110°C to 2-aminoethyl hydrogen sulfate. A shift change led to the base being added to the acid without agitation. When the agitator was started later, reaction of the two cold and viscous layers of acid and base proceeded explosively. 

As mentioned in section 2.2, an electric double layer is formed at the boundary between two immiscible electrolyte solutions as a result of the different tendencies of electrically charged components in each of the phases to pass into the other phase. 

Similar types of electric double layer may also be formed at the phase boundary between a solid electrolyte and an aqueous electrolyte solution [7]. They are formed because one electrically-charged component of the solid electrolyte is more readily dissolved, for example the fluoride ion in solid LaFs, leading to excess charge in the solid phase, which, as a result of movement of the holes formed, diffuses into the soUd electrolyte. Another possible way a double layer may be formed is by adsorption of electrically-charged components from solution on the phase boundary, or by reactions of such components with some component of the solid electrolyte. For LaFa this could be the reaction of hydroxyl ions with the trivalent lanthanum ion. Characteristically, for the phase boundary between two immiscible electrolyte solutions, where neither solution contains an amphiphilic ion, the electric double layer consists of two diffuse electric double layers, with no compact double layer at the actual phase boundary, in contrast to the metal electrode/ electrolyte solution boundary [4,8, 35] (see fig. 2.1). Then, for the potential... 

Liquid-hquid extraction (LLE) is widely used in many aspects of organic chemistry to purify materials. It rehes on the compounds to be separated having different partition coefficients between two immiscible solvents, such that the compound of interest preferentially partitions into one layer relative to the other component. When separating a very polar compound from a very non-polar one, this can yield extremely efficient separation. In less favourable circumstances, only a partial pre-concentration is achieved. Sometimes repetitive extractions can provide the desired pre-concentration, but with compounded losses and thus reduced sensitivity. 

An aqueous biphasic system consisting of two immiscible liquid phases (i.e., two separate distinct layers) can be used to separate a particular component such as certain heavy metals from contaminated soil. A combination of phases such as a water-soluble polymer (e.g., polyethylene glycol) phase and a concentrated aqueous salt solution (e.g., sodium carbonate, sodium sulfate, or sodium phosphate) phase can comprise a biphasic system. Aqueous biphasic systems are... 

Once a quantity of a third substance (solute) is added to a system of two immiscible liquids, it will distribute or divide between the layers in definite proportions. Applying the phase rule to such a system reveals that we have a system of three components (C) and two phases (P). Thus, the system has three degrees of freedom (F), that is, pressure, temperature, and concentration. 

The most common HPLC separation mode is based on separating by differences in compound polarity. A good model for this partition, familiar to most first-year chemistry students, is the separation that takes place in a separatory funnel using immiscible liquids such as water and hexane. The water (very polar) has an affinity for polar compounds. The lighter hexane (very nonpolar) separates from the water and rises to the top in the separating funnel as a distinct upper layer. If you now add a purple dye made up of two components, a polar red compound and a nonpolar blue compound, and stopper and shake up the contents of the funnel, a separation will be achieved (Fig. 1.2). 

Example 7.3 Effect of Viscosity Ratio on Shear Strain in Parallel-Plate Geometry Consider a two-parallel plate flow in which a minor component of viscosity /t2is sandwiched between two layers of major component of viscosities /q and m (Fig. E7.3). We assume that the liquids are incompressible, Newtonian, and immiscible. The equation of motion for steady state, using the common simplifying assumption of negligible interfacial tension, indicates a constant shear stress throughout the system. Thus, we have... 

In this example of model reactive polymer processing of two immiscible blend components, as with Example 11.1, we have three characteristic process times tD,, and the time to increase the interfacial area, all affecting the RME results. This example of stacked miscible layers is appealing because of the simple and direct connection between the interfacial layer and the stress required to stretch the multilayer sample. In Example 11.1 the initially segregated samples do create with time at 270°C an interfacial layer around each PET particulate, but the torsional dynamic steady deformation torques can not be simply related to the thickness of the interfacial layer, <5/. However, the initially segregated morphology of the powder samples of Example 11.1 are more representative of real particulate blend reaction systems. 

Given two partially immiscible liquids b and c, consider a third component (subscript a) which is present in the two liquid layers. If this substance is sufficiently dilute... 

Verwey-Niessen model — Earliest theoretical model of the - interface between two immiscible electrolyte solutions (ITIES) assuming the existence of a diffuse double layer with one phase containing an excess of the positive space charge and the other phase an equal excess of the negative space charge [i] (Figure). The difference of - inner electric potentials, Afcj> = (f>w - [Pg.692]

Apart from fractional distillation, the comparison of the three types may be looked at in another way, if the partially miscible and immiscible cases be considered too. All five cases form a series. In the case of immisc ble liquids the pressure diagram ma r be drawn a priori if at a (Fig. %o) we draw ah for the pressure of one component, and at c draw cd for the pressure of the other component all the mixtures will then have the pressure ae = a + cd. If partial mixture occurs the line heed is altered the verticals he and ed change to the gradual increase shown by he-j and and these are joined by horizontal referring to the two layers of liquid. Since the pressure of each component in the partial mixture must be less than that of the same substance by itself, the line e- e must lie below ee. 

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