Mutual immiscibility

The preceding definitions have been directed toward the treatment of the solid-liquid-gas contact angle. It is also quite possible to have a solid-liquid-liquid contact angle where two mutually immiscible liquids are involved. The same relationships apply, only now more care must be taken to specify the extent of mutual saturations. Thus for a solid and liquids A and B, Young s equation becomes... 

Blends of PET and HDPE have been suggested to exploit the availabiUty of these clean recycled polymers. The blends could combine the inherent chemical resistance of HDPE with the processiag characteristics of PET. Siace the two polymers are mutually immiscible, about 5% compatihilizer must be added to the molten mixture (41). The properties of polymer blends containing 80—90% PET/20—10% HDPE have been reported (42). Use of 5—15% compatbiLizer produces polymers more suitable for extmsion blow mol ding than pure PET. 

Fig. 5. Flow diagram of typical interfacial polymerisation encapsulation process in which reactants X and Y are dissolved in separate mutually immiscible...

A key feature of encapsulation processes (Figs. 4a and 5) is that the reagents for the interfacial polymerisation reaction responsible for shell formation are present in two mutually immiscible Hquids. They must diffuse to the interface in order to react. Once reaction is initiated, the capsule shell that forms becomes a barrier to diffusion and ultimately begins to limit the rate of the interfacial polymerisation reaction. This, in turn, influences morphology and uniformity of thickness of the capsule shell. Kinetic analyses of the process have been pubHshed (12). A drawback to the technology for some apphcations is that aggressive or highly reactive molecules must be dissolved in the core material in order to produce microcapsules. Such molecules can react with sensitive core materials. 

Most pairs of homopolymers are mutually immiscible, so that phase diagrams are little used in polymer science... another major difference between polymers on the one hand, and metals and ceramics on the other. Two-phase fields can be at lower or higher temperatures than single-phase fields... another unique feature. 

Emulsions. Emulsions are formed when one liquid is dispersed as small droplets in another liquid with which the dispersed liquid is immiscible. Mutually immiscible fluids, such as water and oil, can be emulsified by stirring. The suspending liquid is called the continuous phase, and the droplets are called the dispersed (or discontinuous) phase. There are two types of emulsions used in drilling fluids oil-in-water emulsions that have water as the continuous phase and oil as the dispersed phase, and water-in-oil emulsions that have oil as the continuous phase and water as the dispersed phase (invert emulsions). 

The excellent correlation between calculated and experimental log P values was obtained by vast investigations of the partitioning of simple chemicals in different mutually immiscible two-phase liquid systems by means of universal model based on the MOD theory [23] ... 

Ruelle, P. Universal model based on the mobile order and disorder theory for predicting lipophilidty and partition coefficients in all mutually immiscible two-phase liquid systems. Chem. Inf. Comput. Sci. 2000, 40, 681-700. 

When the reactants involved in a step growth polymerization process are mutually immiscible, we can employ an interfacial polymerization method. Two solutions, each containing one of the monomers, are layered one on top of the other. This creates a phase boundary that forms wth the least dense liquid on top. The different monomers can then meet and polymerize at the interface. A commonly demonstrated example of this is the manufacture of nylon 610 by the interfacial reaction between an aqueous solution of hexamethylenediamine with sebacoyl chloride dissolved in carbon tetrachloride. Because the reaction only occurs at the interface, it is possible to pull the products from this interface to isolate the final product. 

A stoichiometric forerunner of this approach was the wolf and lamb reaction, reported by Patchornik and co-workers in 1981 [17]. Two reagents that in solution react with each other quickly to give an undesired product (hence wolf and lamb ) were immobilized on solid polymeric supports (two insoluble and mutually immiscible polymers, Scheme 5.1), rendering them unreactive towards each other. This allowed the formation of the desired product through the use of a messenger reagent. 

One can have the same type of situation in a blend of two mutually immiscible polymers (e.g., polymethylbutene [PMB], polyethylbutene [PEB]). When mixed, such homopolymers form coarse blends that are nonequilibrium structures (i.e., only kinetically stable, although the time scale for phase separation is extremely large). If we add the corresponding (PEB-PMB) diblock copolymer (i.e., a polymer that has a chain of PEB attached to a chain of PMB) to the mixture, we can produce a rich variety of microstructures of colloidal dimensions. Theoretical predictions show that cylindrical, lamellar, and bicontinuous microstructures can be achieved by manipulating the molecular architecture of block copolymer additives. 

AN EMULSION is a mixture of two mutually immiscible liquids, one of winch is dispersed as droplets in the other, and is stabilized by an emulsifying agent. 

The distribution of a solute between two mutually immiscible solvents can be represented by the simple equation,... 

The reasoning applies generally to (degenerate) N-phase equilibrium involving N mutually immiscible species. Whence the cited result for solids. 

Emulsifiers reduce the interfacial tension between two mutually-immiscible liquids because they have an affinity for both phases. Ford and... 

The partition of any molecule of interest M between two mutually distinct (usually this means mutually immiscible) phases (call them phases 1 and 2) is governed, as all equilibrium processes, by an equilibrium constant (the law of Guldberg1 and Waage2) ... 

In the previous sections, methods of qualitatively controlling the course of propagation were described. Indirect control as well as the quantitative effects caused by intentional control of the other partial processes in polymerization have still to be mentioned. The separation of initiation from propagation alters the kinetic character of the whole reaction. With ionic polymerizations, initiation can be separated from propagation by the selection of conditions suitable for rapid initiation. With radical polymerizations, this is not possible. Therefore both partial processes must be separated in space. Fortunately, radical active centres operate both in polar and in non polar media. Thus it is not difficult to confine initiation and propagation to mutually immiscible components of the medium. Emulsion polymerization remains the most important representative of quantitative control of propagation. 

Block copolymers are also formed by condensation of two chain types with functional end groups. Some kinds of polyurethanes are examples. Dissimilar and mutually immiscible polymers can be connected in this way. Henderson and Szwarc condensed a, co-polystyrenedicarboxylic acid with a polyamide carrying terminal amino groups [272], producing the copolymer poly-(styrene)-6/ocfc-poly(amide). The condensation was slow the probability of finding functional groups at an effective distance is small. 

Figure 4.22 Schematic drawings of various block copolymers. These long-chain molecules synthetic molecules consist of chemically distinct poiymeric "biocks" (denoted by lines of (Afferent thicknesses in the figure), chemically grafl. (Left to right ) Linear diblock copolymer molecule (AB) linear triblock (ABC) star copolymer brush copolymer. If the blocks are mutually immiscible, under suitable conditions die molecules spontaneously dump together forming an array of mesophases.

III) Two mutually immiscible media (countercurrent chromatography). When two mutually immiscible media... 

The enzymatic polymerization proceeded even in a biphasic system consisting of two mutually immiscible phases (isooctane and water).23 In the polymerization of p-alkylphenols in this system, the molecular weight increased as a function of the carbon number of the alkyl group. 

Several criteria must be considered in the selection of the diluent solvent. The first one is biocompatibility, that is, the solvent must not be toxic to the biodegrading microorganism [10]. The second criterion is the resistance to biodegradation and/or utilization by the active microorganism used, that is, so-caUed (non)bioavailability [8]. Third criterion is the favorable mass-transfer characteristics for the biodegraded pollutant [1], and the fourth criterion is the mutual immiscibility of the diluent with the treated waste-water [1]. The fifth criterion is the hmited volatility of the diluent [11]. 

The fourth criterion of mutual immiscibility of the diluent and the feed phase is important for several reasons. The lower the diluent solubility in the treated wastewater, the less likely it is that diauxic growth or co-metabolism wiU occur [34]. The lower the solubility of the diluent in the feed phase, the higher the recovery of the diluent at the end of the treatment of one batch of the feed phase, that is, wastewater. This reduces losses of the diluent used, thus treatment costs are lower due to decreased costs of solvent procurement. 

Examples of liquid-in-gas dispersions are the mist, the clouds, and other aerosols. Liquid-in-liquid dispersions are the emulsions. At room temperature there are only four types of mutually immiscible liquids water, hydrocarbon oils, fluorocarbon oils, and liquid metals — Mercury (Hg) and gallium (Ga). Many raw materials and products in food and petroleum industries exist in the form of oil in water or water in oil emulsions. The soil and some biological tissues can be considered liquid-in-solid dispersions. 

Partitioning. A substance may have limited solubility in two mutually immiscible solvents, for instance water and oil. This often happens in foods, for example with many flavoring and bactericidal substances. It then is important to know the concentration (or rather activity) in each phase. For low concentration, the partitioning or distribution law of Nernst usually holds ... 

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