Fractional solubility parameter solvent

The fraction of the net solubility parameter that is dispersive, polar, or hydrogen bonding is called fractional solubility parameter. Graphical representations of these fractional parameters on triangular graph paper are referred to as TEAS graphs. Solvent blends can be selected to dissolve a polymer by matching the solubility parameter values. 

When viscometric measurements of ECH homopolymer fractions were obtained in benzene, the nonperturbed dimensions and the steric hindrance parameter were calculated (24). Erom experimental data collected on polymer solubiUty in 39 solvents and intrinsic viscosity measurements in 19 solvents, Hansen (30) model parameters, 5 and 5 could be deterrnined (24). The notation 5 symbolizes the dispersion forces or nonpolar interactions 5 a representation of the sum of 8 (polar interactions) and 8 (hydrogen bonding interactions). The homopolymer is soluble in solvents that have solubility parameters 6 > 7.9, 6 > 5.5, and 0.2 < <5.0 (31). SolubiUty was also determined using a method (32) in which 8 represents the solubiUty parameter... 

As already mentioned molecules cohere because of the presence of one or more of four types of forces, namely dispersion, dipole, induction and hydrogen bonding forces. In the case of aliphatic hydrocarbons the dispersion forces predominate. Many polymers and solvents, however, are said to be polar because they contain dipoles and these can enhance the total intermolecular attraction. It is generally considered that for solubility in such cases both the solubility parameter and the degree of polarity should match. This latter quality is usually expressed in terms of partial polarity which expresses the fraction of total forces due to the dipole bonds. Some figures for partial polarities of solvents are given in Table 5.5 but there is a serious lack of quantitative data on polymer partial polarities. At the present time a comparison of polarities has to be made on a commonsense rather than a quantitative approach. 

Where, x,- is the volume fraction of component /, S, and S/ are the solubility parameters of the homogenous solvent mixture and the component i, respectively. The solubility parameters of some solvents that are widely used as the continuous medium in the dispersion polymerization are given in Table 6. 

The solubihty parameter theory can be also used for the mixed-solvent systems. The total-solubility parameter 8, is given by the sum of the individual solubihty parameters in terms of the volume fractions (pj in the mixture, according to Equation 4.6 ... 

The crude oil produced from the Main Zone of the Torrance Field has an API gravity of 18° and contains 5.3 weight percent asphaltenes. The solubility of the asphaltene molecules in Main Zone oil was measured by the Oliensis Test(35). In this test, the solubility parameter Qf ie oil was lowered by adding to the oil successively larger volumes of hexadecane, a poor solvent for asphaltene molecules. The minimum volume (in milliliters) of hexadecane, which when added to 5 g of crude oil, will cause the chromatographic separation of the asphaltene fraction is termed the Oliensis Number. The Oliensis Number for the Main Zone crude oil is 3, indicating that the asphaltene molecules are not well-solubilized in the oil. Small changes in the solubility parameter of the Main Zone oil can cause the asphaltenes to precipitate. 

If Z9b(ai) can be equated with P calculated from the entries in Table 2.5, then Z9b(a2) in any other solvent Ab can be estimated from Eq. (2.62). Equation (2.62) is actually a combination of four expressions of the form of Eq. (2.8) (see section 2.2.2), two for water and solvent Ai and two for water and solvent A2, presuming them to be immiscible pairs of liquids. It employs concentrations on the mole fraction scale, and assumes that the systems behave as regular solutions (which they hardly do). This eliminates the use of the solubility parameter 8 of water, which is a troublesome quantity (see Table 2.1). Solvent Ai need not, of course, be 1-octanol for Eq. (2.62) to be employed, and it suggests the general trends encountered if different solvents are used in solvent extraction. 

Table 6.2 presents data showing the effect of various CMOS on the activity coefficient or mole fraction solubility of naphthalene, for two different solvent/water ratios. To examine the cosolvent effect, Schwarzenbach et al. (2003) compare the Hildebrand solubility parameter (defined as the square root of the ratio of the enthalpy of vaporization and the molar volume of the liquid), which is a measure of the cohesive forces of the molecule in pure solvent. 

Different surfactants are usually characterised by the solubility behaviour of their hydrophilic and hydrophobic molecule fraction in polar solvents, expressed by the HLB-value (hydrophilic-lipophilic-balance) of the surfactant. The HLB-value of a specific surfactant is often listed by the producer or can be easily calculated from listed increments [67]. If the water in a microemulsion contains electrolytes, the solubility of the surfactant in the water changes. It can be increased or decreased, depending on the kind of electrolyte [68,69]. The effect of electrolytes is explained by the HSAB principle (hard-soft-acid-base). For example, salts of hard acids and hard bases reduce the solubility of the surfactant in water. The solubility is increased by salts of soft acids and hard bases or by salts of hard acids and soft bases. Correspondingly, the solubility of the surfactant in water is increased by sodium alkyl sulfonates and decreased by sodium chloride or sodium sulfate. In the meantime, the physical interactions of the surfactant molecules and other components in microemulsions is well understood and the HSAB-principle was verified. The salts in water mainly influence the curvature of the surfactant film in a microemulsion. The curvature of the surfactant film can be expressed, analogous to the HLB-value, by the packing parameter Sp. The packing parameter is the ratio between the hydrophilic and lipophilic surfactant molecule part [70] ... 

The factors that cause solutions of iodine to deviate from die behavior of regular solutions are illustrated in Fig. 3. in which values of the left hand member of Eq. (7) are plotted against those of the right for iodine solutions at 25°C ai is tire activity of solidiodine Xy denotes measured solubility Vy is the extrapolated molal volume of liquid iodine. 59 cra3 i is the volume fraction of the solvent, 1.0 62 = 14.1 1 is the solubility parameter of the solvent. Illustrative values of xi and 6] are given in accompanying table. 

Lin and Nash (1993) have proposed an equation to estimate the Hildebrand solubility parameter of a solute strictly from its mole fraction solubilities and their respective solvent solubility parameters ... 

If this activity coefLcient term is applied to Equation 2.41, the mole fraction solubility can be shown to reach a maximum wh00i equals5D2, < pi equals, and< m equals - Teas (1968) presented a triangular plot where the sides represent the three contributions to the solvent solubility parameter. For example, the dispersion force contribution would be... 

There are several theoretical models to estimate the solubility of a solute in a solvent. However, use of dielectric constant is one of the oldest and simplest approach and is very popular with the formulators. Fractional method to estimate the dielectric constant is the simplest approach and is not the most accurate. However, it offers a good starting point for the estimation. In addition, the solubility of a solute is dependent on the dielectric constant of a solvent mixture and not to the particular composition. Other approaches, such as solubility parameter method and UNIFAC group theory contributions are less frequently used by industry formulators. 

In order to attempt to remove some of these potential ambiguities, more recent developments of this concept have focused on the solubility parameter. The simplest map that can be derived using the solubility parameter is produced with the solubility parameters of the solvents used in solvent separation procedures, and equating these parameters to the various fractions (Figure 3-17). However, the solubility parameter boundaries determined by the values for the eluting solvents that remove the fractions from the adsorbent offer a further step in the evolution of petroleum maps (Figures 3-18 and 3-19). 

Figure 3-17 Assignment of solvent solubility parameters to petroleum fractions.

When the only effects that have to be taken into account are those of cavity formation in the solvent and the dispersion interactions, i.e., when both the solvent and the solute are non-polar, then Hildebrand s solubility parameter concept (Hildebrand and Scott 1950) provides good estimates of the solubility. The mole fraction of a gaseous solute, x2, in a solution in equilibrium at a partial pressure p2 of this gas, can be estimated from the following expression ... 

A simple expression governs the solubility of a liquid solute in a solvent, provided the solvent is practically insoluble in the liquid solute and that, again, only dispersion forces are operative between them. The first condition yields for the activity of the solute in its practically neat liquid phase, as well as in the saturated solution in equilibrium with it, to a2 1 and In a2 0. This dispenses effectively with the first term on the right hand side of Eq. (2.10). For a given liquid solute, the solubility parameter of the solvent dictates the solubility and constitutes entirely the solvent effect on it. This fact has found much application in the determination of the solubilities of certain liquid polymers in various solvents, the mole fraction x2 and volume V2 then pertain to the monomer of the solute. If, however, the solvent is also soluble in the liquid solute, as is the case when a solvent is capable of swelling a polymer, then the mutual solubility is given by ... 

Thus, one approach to understanding the chemistry of pyrolysis of pitch leading to mesophase is not to make a complete molecular analysis but to solvent fractionate the pitch using solvents of increasing solubility parameters (58). An early study of fractionation and NMR analysis of fractions is that of Smith et al. (61). 

The polarity index or the solubility parameter may be used as a measure of solvent strength, which would be a measure of polarity in those cases. For reversed phase HPLC, solvent strength parameters have been proposed for the four most common solvents used, i.e. water (Si = 0), methanol (Si = 2.6), acetonitrile (Si = 3.2) and THF (Si = 4.5). Using these values water makes no contribution to the eluting power of the mobile phase and the solvent strength is measured by the volume fraction of organic modifier. 

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