Problem of phase separation

Owing to this problem of phase separation, gasoline/ethanol blends should be not exposed to water during distribution or use in a vehicle. For this reason, they cannot be transported in pipelines, which sometimes contain water. This water sensitivity also means that extra care should be taken when gasoline/ethanol blends are used as a fuel for boat engines. 

The problem of phase separation in cuprates superconductors has been longely debated [1-8], Recently, several experiments show the formation of electronic crystals at critical densities [9, 10], These results provide a strong experimental support for the scenario proposed some years ago (11-14) for the phase diagram of cuprate superconductors where generalized Wigner... 

More examples include the use of Ir(III) complexes in dendrimers [136] and as pendants in oligo- or polymeric lluorene (or carbazole), in part already discussed in Sect. 3.4 [76,137,138]. Both cases illustrate viable methods to solve the problem of phase separation in electroluminescent polymers doped with Ir(III) complexes and are not treated here in detail. 

In the nitride alloy systems, accurate measurement of the chemical composition is yet to be developed. SIMS can provide precise determination of the alloy composition, but it is complicated by the matrix effect of the element as well as the difficulties in growing the alloys. The problem of phase separation associated with the growth of InGaN and the mixed group V alloys needs to be addressed. 

Neat methanol and ethanol fuels do not present the problem of phase separation since water is soluble in these alcohols in all proportions except at very low temperatures. Interestingly, it is not necessary to use anhydrous neat alcohol fuels in spark-ignition engines. The neat ethanol-fueled automobiles in Brazil operate with 190 proof ethanol (95 vol %), which precludes the energy-consuming step of producing anhydrous ethanol. Indeed, the addition of 10 and 20 wt % water to methanol raises its octane value to about 107 and... 

This experimental difficulty was overcome by simulating the behaviour of a model system and a biaxial nematic phase was indeed obtained [122], One way by which the problem of phase separation could be solved experimentally was suggested by Fletcher and Luckhurst and involved covalently linking a rod-like and disc-like unit via a flexible spacer yielding a non-symmetric discotic-calamitic liquid crystal dimer [123] ... 

Besides the topological aspects of polymer formation in seeded emulsion polymerization, the problems of phase separation during polymerization create a more complex dependence of the particle morphology on polymerization parameters and conditions in the case where the composite latex particles comprise two or more immiscible polymers. During the past several years there have been a significant number of studies which have been dedicated to the elucidation of the... 

The previous section reviewed the elements of statistical mechanics that are important in thinking about the structures, fluctuations, and phase behavior of surfaces, interfaces, and membranes. In this section, we consider an important application of these ideas to the problem of phase separation in binary mixtures. This problem is analogous to other types of phase transitions, such as those found in Ising magnets. It is important to understand the specific problem of phase separation because it is this phenomenon that results in the equilibrium between two coexisting states, which naturally gives rise to the existence of interfaces. 

As mentioned above, tackifiers and/or plasticizers are often used as part of many PSA formulations, most particularly in synthetic and natural rubber PSAs. Tackifiers and plasticizers are low molecular weight compoimds that are compatible with the base polymer of the PSA. They act as a diluent in the base polymer of the PSA because they are not part of the pol5meric network made up by the base polymer (30). They must be compatible with the base polymer to avoid problems of phase separation. In particular, if the tackilier/plasticizer has a lower surface energy than the base polymer, then phase separation can create a layer of pure tackifier/plasticizer on the surface of the PSA and destroy the tack of the formulation. The most common tackifiers are based on rosin acids, small-chain hydrocarbons, and terpenes. 

Horizontal piping systems used to collect and transport well fluids introduce problems of phase separation resulting in stratified corrosive water and gas phases that complicate inhibition control and monitoring. In addition, there is the possibility of oxygen and bacterial (SRB) contamination that can accelerate corrosion. Control of internal corrosion of steel surface piping generally involves inhibition or plastic lining. 

As already noted, the volume of a liquid-liquid reactor for a given output is calculated using the same principles as outlined for gas-liquid reactors. One major factor to be considered in liquid-liquid reactions, however, is the much smaller density difference between the two phases as compared to gas-liquid reactions. While this is, in general, conducive to creating greater interfacial area, too small a difference is likely to cause problems of phase separation. This often leads to emulsion formation and the consequent attention to designs that promote emulsion breaking. 

The general problem of phase separation, due to freeze-thaw cycles, is further discussed in the following section VII.H. 

Mixtures of discs and rods have been predicted to form a biaxial nematic phase [20]. Avoiding the problem of phase separation between the two moieties, chemically linked disc-rod molecules have been studied. Optical textures, miscibility studies, and DSC experiments all resulted in the conclusion that, for a mixture with a certain ratio between the combined mesogen and the pure disc mesogen, a biaxial nematic phase had indeed been found [28]. However, this conclusion will have to be confirmed using additional experimental techniques, as, for example, deuterium NMR spectroscopy. 

OnsaGER treated the problem of phase separation from a completely different point of view and succeeded in showing that phase separation may be due partly to entropy effects. Also in his calculation, however, ail interactions are described as interactions by pairs which enables him to find the analogue of the second virial for colloidal systems and this is in principle enough to describe phase separation. 

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