Phase separation effects

Most reported PPLEDs were fabricated by doping a polymer with a phosphorescent dye. However, aggregation and phase separation effects may cause serious problems for device performance and aging. In this section, we describe the very recent progress in intrinsically electrophosphorescent polymers containing triplet-emitting complexes either as pendant substituents or as a part of a backbone. 

Different biopolymers are used when the texture-building capacity of protein alone, for instance, is insufficiently capable to create the target structure. However, phase separation effects can occur, as described in theory and technical detail in other chapters of this publication. These phenomena are also dependent on processing factors such as heat or mechanical treatment, the latter effects being rarely investigated so far. 

O. R. Adlof, Normal-phase separation effects with lipids on a silver ion high-performance liquid chromatography column,/. Chromatogr. A 764 (1997),337-340. 

The integration of all these five factors will be important in relation to a deeper understanding of processing behaviour. All that has been said so far applies to a single-phase polymer, although it must be remembered that commercial polymers can have broad molecular mass distributions and there is scope for phase separation effects to be present even within a single species material. Polymer blends suspensions and foams all add to the additional complexity of the problem. 

Von Damm, 2003) (Table 2.5). This complicates interpretation of the data, which are sometimes presented on a constant Cl basis to distinguish phase separation effects from changes due to chemical reactions. 

Tsuru, T. et al., Titania membranes for liquid phase separation Effect of surface charge on flux, Separ. Purif. Technol., 25, 307, 2001. 

The phase separation experiments were conducted at 30.00°C by titrating the starting polymer solutions with base until turbid. The value of a at incipient turbidity, aT, was sharp and reproducible. Back-titration of a turbid solution with hydrochloric acid caused the solution to become clear exactly at aTi indicating the reversibility of the phase separation effect. 

The importance of these kinetic phase-separation effects will depend strongly on the relative concentrations of the components, of course, since the kinetics of every elementary step leading to gel formation are concentration dependent. From the point of view of creating functional materials that require site accessibility, the base-catalyzed situation is preferable. Unfortunately for those apphcations that rely on optical properties as well as site accessibihty (such as fabrication of optically based sensors), the use of base catalysis typically affords opaque materials. For catalysis and separations applications, however, the optical properties are of little importance (except for characterization of the... 

Another advantage of thermoplastic binder systems over solvent-based ones is the contour accuracy of the extruded material which permits easy fabrication of fine structures (e.g. thin-walled tubes, micro-tools). For such fine structures with very small cross-sectional areas, extrusion pressures can be as high as 700 or 800 bar, and at such high pressures phase separation in feedstocks with solvent-based binder systems can occur. Even for higher pressures such phase separation effects are generally not observed when using thermoplastic binder systems. 

Khare V, Greenberg A, Krantz W. Vapor-induced phase separation—Effect of the humid air exposure step on membrane morphology Part I. Insights from mathematical modeling. J Membr Sci. 2005 258(1-2) 140-156. 

C. Gas-Gas Equilibria.—The term gas-gas equilibria or immiscibility of gases has been attributed to some phase-separation effects in fluid mixtures at high pressures and temperatures, especially above the critical temperature of the less volatile substance. - ... 

Whereas gas-gas equilibria had been a curiosity of phase theory as lately as 10 years ago they have now proved to be as important as the classical types of gas-liquid and liquid-liquid equilibria. They are not at all restricted to some special cases but represent the normal type of two-phase equilibrium in systems of components that differ considerably in size, shape, volatility, and polarity, and consequently show a low mutual solubility even up to rather high temperatures. Thus, fluid systems where the phase-separation effects have to be attributed to the solubility of gas in a liquid (or of a liquid in a gas) at normal conditions of temperature and pressure will frequently exhibit gas-gas critical phenomena at higher temperatures some examples for binary mixtures of He, N2, CH4, CO2, etc. with organic liquids and liquid water are given in Sections 2 and 3.f... 

Time dependent effects on the material functions, that show a time dependent alteration of the viscosity, are widely known from medical, cosmetic, and pharmaceutical industries. For nearly all of these applications, substances usually consist of three or more ingredients, so that these aging effects are usually due to variations in the crystallinity or phase separation effects. 

Adlof, R. O. (1997) Normal-Phase Separation Effects with Lipids on a Silver Ion High-Performance Liquid Chromatography Column, J. Chromatogr. A. 764,337-340. 

Tsuru, T., Hironaka, D., Yoshioka, T., and Asaeda, M. (2003). Titania membranes for liquid phase separation effect of surface charge on flux. Sep. Purif. Technol. 25(2001) 307-314. Soria R., and Cominottim, S. (1996). Nanofiltration ceramic membranes, Proceedings of Fourth International Conference on Inorganic Membranes, pp. 194-197. 

The same group has also observed enhanced impact and toughness behaviour of the blends due to the secondary phase separation effect on the same rubber-modified system. The effect is originated due to the combined effect of hydrodynamics, viscoelastic effects of the rubber phase, diffusion, surface tension, polymerisation reaction and phase separation. In a dynamic asymmetric system, the diffusion of the fast dynamic phase is prevented by the slow dynamic phase, and hence the growth of the fast dynamic phase is retarded by the slow dynamic phase. In the case of low viscosity blends the... 

Frequently, phase separation effected upon incorporation of additives or cosolvents is a major concern when developing novel fuel formulations. Microemulsion-based mixtures can overcome this problem, and has been the focus of more recent works. In that respect, Friberg and Force, in 1976, patented a diesel-based microemulsion formulation that could be used as fuel, with reduced NO emissious when compared to pure diesel [52]. Subsequent works have focused on phase behavior, stability, and performance of different mixtures, most of which involving surfactant-based mixtures [26,39], but it is worth considering the recent advances in the use of microemulsified systems incorporating other fluids like vegetable oils and alcohols. 

Srebnik, S., O. Lev, and D. Avnir, 2001. Pore size distribntion indnced by micro-phase separation Effect of the leaving group during polycondensation. Chem Mater... 

Nanaoscale phase separation effects near r=2.4 and 2.67, and rigid transitions in chalcogenide glasses, C. R Chime, 5, 713-724 (2002). 

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