Attraction constants

Some molar attraction constants compiled by Small are given in Table 5.8. 

Good-GLrifalco-Fowkes (GGF) equation Using ysi = ysv + yiv - 20(ysvyiv) in Young s equation leads to 1+COS0 2 Uvj Yggf obtained from a plot COS0 versus 4> is solid-liquid interaction parameter 0 = 1 if the interactions are purely dispersive. Based on Berthelot relation for attractive constants valid only when the solid-liquid interactions are dominantly dispersive. [77-82]... 

It is possible to calculate the solubility parameter and the solubility parameter components of almost all molecules and polymers by a group contribution method (Van Krevelen, 1990 Bicerano, 1996). For this purpose, as explained by Van Krevelen (1990) it is useful to introduce the molar attraction constant simply defined as ... 

To incorporate the surfactant structure concept, it is now convenient to introduce the group additive concept for cohesive energy densities (CED) introduced by Burrell and others (24, 25). Molecular segments are given a molar-attraction constant G. The CED is then determined for the ith compound as... 

Another aspect of this quasi-thermodynamic approach is to use Equation 25, along with G values from Table 4, to calculate the molar-attraction constant for the sodium sulfonate molecular group or... 

Beerbower equation and the additivity concepts of molar-attraction constants for determining the cohesive energy density. 

A direct measure of nonpolar character of a hydrocarbon molecule is given either by its molar solubility in water or by its molar attraction constant (Small s number) as given by Small... 

Because the heat of vaporization of a polymer is not readily obtained. Small determined values for various components of a polymer chain to calculate the solubility parameter. These values are called molar attraction constants and are additive and have been used for estimation of the solubility parameter for nonpolar polymers. In this approach 8 = D%G/M, where D is density, G are the Small molar attraction constants, and M is the molecular weight of the particular repeat unit. As expected, the more polar units have greater G values while the less polar units have smaller G values. 

G Gibbs free energy modulus molar attraction constant... 

THERMODYNAMICS OF CONDENSED PHASES Table 2.1 Molar Attraction Constants... 

Molar refractivity x ionization potential or molar refractivity alone, Hildebrand s molar attraction constant, or parachor... 

The 8 value of a polymer may also be calculated from Small s relationship, in which 2G is equal to the summation of the molar attraction constants of the individual repeating units constituting the polymer ... 

Polyacetylene attracts constant attention as an excellent simple model of the polyconjugated polymer on which the main optical and electrical properties can be verified. The possibility of achieving metallic conductivities by doping opens real perspectives of practical application of conducting polymers. The complication is the strong interaction with oxygen. The reproducibility of results strongly depends on the synthesis and measurement conditions. 

The alternative method is to calculate 8 for the polymer from the structural formula and the density of the polymer by using the molar attraction constants tabulated by Small (28). 

From this equation, we can see that the total nonideality correction (in braces) contains a negative contribution (first bracketed term) that is indeed proportional to the attractions constant a, while the positive contribution (second bracketed term) is proportional to the finite-volume repulsions constant b, as was supposed in the interpretation of experimental Z behavior in Fig. 2.2. One can also see that the attractions term is linearly proportional to density n/V, whereas the repulsions term is proportional to squared density (,njV)2, so that the former must always prevail at low density (low P) and the latter at high density (high P), as was shown in Fig. 2.2. Furthermore, one can recognize from the 1 /RT prefactor that the entire nonideality correction must diminish with increasing P, as was noted in Fig. 2.3. Thus, regardless of the particular values chosen for a and b, the Van der Waals equation is expected to exhibit both pressure and temperature dependences that are qualitatively consistent with the observed Z(P, T) behavior. 

The molar attraction constants of dispersiS, dipole-dipole interactionsFpi hydrogen bonding,Ehi and the molar volume/ forthe drug and the hydrophobic block may be determined from group contribution tables provided by Hoftyzer-Van Krevelen and Fedor (Krevelen, 1990). 

Molar Attraction Constants F for Functional Groups of Chemical Compounds... 

Earlier, Small (1953) had demonstrated that the combination (Ecoh/V(298))1/2 = F, the molar attraction constant, is a useful additive quantity for low-molecular as well as for high-molecular substances. His set of values is very frequently applied. Accordingly, the corresponding solubility parameter is < smaii = F/V. Later Hoy (1970) proposed group contributions to F, slightly different from those of Small. 

The solubility parameter of a given material can be calculated either from the cohesive energy, or from the molar attraction constant F, as <5 = F/V... 

This means that for the prediction of <5d the same type of formula is used as Small proposed for the prediction of the total solubility parameter 8. The group contributions Fdi to the dispersion component Fd of the molar attraction constant can simply be added. 

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