Cohesive energy density , miscibility

CED) of a polymer, closer to that of CO2, increased the solubility (lowered the miscibility pressures) in CO2. O Neill theorized that solubility is thus not controlled by polymer-C02-specilic interactions, but mainly by poor polymer-polymer interactions, and that a low cohesive energy density (reflected by a low surface tension) of a polymer primarily determines its solubility in CO2. In a U.S. patent issued in 1998, Johnston et al. demonstrated that surfactants based on poly(propylene oxide) and poly(butylene oxide) were also quite soluble in CO2 (39). The invention was significant for demonstrating that nonfluorinated surfactants can exhibit appreciable solubility in CO2. 

Compressed CO2 is completely miscible with numerous organic solvents and, upon contact, lowers the cohesive energy density of the organic solvent and reduces its solvent power. At the same time, compressed CO2 is a poor solvent for many solids. These two properties of compressed CO2 make it a good antisolvent for a variety of substances. Most processes that exploit the antisolvent properties of CO2 involve, as a first step, the dissolution of the... 

The extent to which these polymer-solvent intemctions may control the miscibility of a system has been described for some time in terms of the solubility parameter, 6. In simple liquids, this has a direct link to the cohesive energy density (AE/V) of the material ... 

It is a popular lore that the introduction of some fluorine atoms or a short perfluoroalkyl group results in increasing lipophilicity. A classical parameter 8, Hildebrand s solubility parameter, which is the square root of the cohesive energy density, has been used for miscibility estimation [2]. If two liquids have similar values for 8, i.e. if (Si —S2)2 is small, they are miscible. 

As discussed above, the solubility parameter is usually assumed to be equal to the square root of the cohesive energy density. It thus encompasses all of the different types of forces of cohesion in a material. Sometimes, however, the solvation of a polymer by a solvent, the behavior of plasticizers, pigments and other additives, or the blending of two polymers, requires certain specific types of interactions to exist between the polymer and the solvent, or between the two polymers that are to be blended. In such cases, the matching of the strengths of these specific types of interactions may play a crucial role in solvation or miscibility, and a more refined treatment may be necessary than can be provided by a single-valued solubility... 

Cyclic bisphenol-A polycarbonate oligomers have been reported by Kambour et al. [1994] to be miscible with a broad range of polymers (cohesive energy density, CED = 300 - 500 MJ/m ) (much broader than linear PC). The cyclic oligo-... 

The square root of the cohesive energy density is termed the solubility parameter d. It is also a measure of the intermolecular forces in pure substances. Solvents with comparable solubility parameters have similar interaction forces and are therefore readily miscible and mutually soluble. In order to take account of not only the dispersion forces but also of the polar forces and hydrogen bonds, the solubility parameter is resolved into the following components [14.26], [14.27] ... 

Miscible blends should have greater mechanical integrity than a comparable multiphase structure. Miscible rubber blends that react chemically have a densiflcation and a higher cohesive energy density. This may provide improved mechanical properties but has been observed only below the Tg (Kleiner et al., 1979). 

The concept of the solubility parameter 6, which is frequently used in studies of polymer compatibility, is not always applicable. The solubility parameter is equal to the square root of the substance s cohesion energy density (6 = VDEC) and reflects only intermolecular interaction without accounting for the entropy factor. This parameter is an integral characteristic of only intermolecular interaction, and the components miscibility is determined by the presence of functional groups capable of specific interactions in the polymer molecules. This is why... 

The quantity zcoIkT is the Flory interaction parameter, x- Another quantity, which should be mentioned because of its frequent use in the prediction of solubilities in polymer systems, is the solubility parameter, 6. Optimum miscibility occurs when polymer and solvent have the same value of 6. 6 is defined as the cohesive energy density of the material. Its value will change with temperature and pressure, but, in its simplest form, the approach gives the enthalpy of mixing as ... 

Calculation of solubility parameters (5) for a drug and a polymer have been used as a method for predicting miscibility in amorphous solid dispersions (Hancock et al. 1997), using, for example, the Hildebrand solubility parameter (Greenhalgh et al. 1999), which was calculated from the cohesive energy density (CED) by ... 

A computational model based on molecular dynamics was developed to predict the miscibility of indomethacin in the carriers polyethylene oxide (PEO), glucose, and sucrose (Gupta et al. 2011). The cohesive energy density and the solubility parameters were determined by simulations using the condensed-phase optimized molecular potentials for atomistic simulation studies (COMPASS) force field. The simulations predicted miscibility for indomethacin with PEO (A5 < 2), borderline miscibility with sucrose (A5 < 7), and immiscibility with glucose (A5 > 10 Table 2.2). 

White RP, Lipson JEG (2014) Free volume, cohesive energy density, and internal pressure as predictors of polymer miscibility. Macromolecules 47(12) 3959-3968... 

The stiffness of a solvent is defined as UIV-P., where UA is the cohesive energy density and is the internal pressure (Section 3.3.1). Of the water-miscible solvents, only the two ethers, tetrahydrofuran and 1,4-dioxane, and the amide HMPT are non-stiff (entries in italics in the second column in Table 3.8). This property bears on the energetics of introducing a solute (an ion) into a cavity that has to be formed in the solvent to accommodate the solute—the larger the stif iess, the more energy has to be invested in the formation of the cavity. 

The solvent power or solvency of a given liquid or mixture of liquids determines the miscibility of the polymer binder or resin. It has also a big effect on the attraction between particles in a paint formulation as will be discussed below. A very useful parameter that describes solvency is the Hildebrand solubility parameter 8 [2] which is related to the energy of association of molecules in the liquid phase, in terms of "cohesive energy density . The latter is simply the ratio of the energy required to vaporize 1 cm of liquid AE, to its molar volume V . The solubility parameter 6 is simply the square root of that ratio [2,3],... 

Cohesive energy density and solubility parameters are defined in the section on miscibility of solvents and polymers (Section B). In addition, the applicability of solubility parameters to thermodynamic calculations and their limitations are discussed. Section C contains methods for measuring, calculating and correlating solubility parameters of solvents and polymers. Section D contains... 

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