Solubility parameters, recent

Extensive use of the three-dimensional solubility parameters for predicting adhesion seems not to have been made, although its additional flexibility should make it successful over a wider range of conditions than the single-parameter approach. Some recent studies involving dental adhesion employed the method with success. Asmussen and Uno fl40 successfully correlated the shear bond strength of various dental adhesive resins, characterized in terms of their three-... 

Lohse et al. have summarized the results of recent work in this area [21]. The focus of the work is obtaining the interaction parameter x of the Hory-Huggins-Stavermann equation for the free energy of mixing per unit volume for a polymer blend. For two polymers to be miscible, the interaction parameter has to be very small, of the order of 0.01. The interaction density coefficient X = ( y/y)R7 , a more relevant term, is directly measured by SANS using random phase approximation study. It may be related to the square of the Hildebrand solubility parameter (d) difference which is an established criterion for polymer-polymer miscibility ... 

Siemann (27) recently determined the solubility parameters and densities of a group of biodegradable polyesters. Solubility parameters... 

Pioneering work on the application of this theory for correlating and predicting distribntion ratios was done in the 1960s [38a-40c]. Several reviews on the nse of this theory for two-phase distribution processes are also available [41,42]. Recently this theory has been refined by the use of Hansen solubility parameters [6,43,44], according to which... 

In addition to the solubility parameter model to treat SEC adsorption effects, an approach based on Flory-Huggins interaction parameters has also been proposed (24-27). For an excellent review of both mechanisms, see reference 28.- A general treatment of polymer adsorption onto chromatographic packings can be found in Belenkii and Vilenchik s recent book (29). 

Of course, the practical result of gel formation is an inability to mix the reagents (10. 52. 57. 58). However, it has recently been reported that this tendency to form gel can be greatly reduced by use of special solvents with solubility parameters of 7.2 e.g.,... 

Liquids with equal solubility parameters are miscible, there is no heat of mixing. With increasing difference of <5, two phases coexist, which become miscible at elevated temperature, at the critical consolute temperature Tc. Tc increases with the difference of the <5 s and with the mean molar volume of the two liquids. Another polarity scale was recently introduced by Middleton and co-workers13 based on the bathochromic shift of UV-visible 2max. The obtained spectral polarity index ranks the solvents at one end of the scale is the nonpolar perfluorohexane and at the opposite the highly polar and acidic l,l,2,3,3.3-hexafluoropropan-2-ol. The latter is much more polar than its hydrocarbon analog. 

In a recent study by Lee (1996), LSER were combined with an extended Hildebrand solubility equation. From a comparison between LSER and the extended solubility parameter model, it has... 

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). 

Recently Yuan et al. found a dependence of MWD on the solubility parameter of the medium in the slurry polymerization of propylene over TiCl3(AA)— Al(C3H5)2a. 

Other molecular properties have been also proposed to model the hydrophobic interactions. The parachor, which is related to the surface tension of a compound (139, 140) represents mainly the intermolecular interactions in a liquid. The Hildebrand-Scott solubility parameter, 6, (141) is related to intermolecular van der Waals forces and the closely related molar attraction constant, F, is obtained by multiplying 6 by the molar volume (142). The partition coefficient between two solvents can be obtained from the solubility parameters and the molar volumes of the solute and the solvents (193). This relationship is based on regular solution theory (194) and the assumption that the partial molar volumes of the solute is not different from its molar volume. Recently this has been criticized and a new derivation was proposed (195) in which the partial molar volumes are taken into account. The molar refractivity, MR, is related to dispersion forces and can be obtained as a sum of the partial molar refractivi-ties assigned to atoms and bonds (140, 143). These parameters have been compared (144) to establish their relative applicability to correlations with biological activity. The conclusion was that logP and molecular refractivity were the best parameters. Parameters obtained from high pressure liquid chromatography (144,... 

Very little data on the Hildebrand solubility parameters of ionic liquid-solute systems is available to date. A study of eight ionic liquids using viscosity measurements in different solvents indicated polarities similar to allyl alcohol or dimethylsulfoxide [35], More recent work has shown that the solubility parameters can be reliably estimated from surface tension and density measurements [36], The equilibrium position of keto-enol tautomers in conjunction with quantitative H-NMR-, IR- and UV/Vis-spectroscopy has been studied in ionic liquids [37, 38], where the stabilisation of the enol form is favoured in non-polar solvents in general. Comparison to the relative tautomer ratios obtained in methanol and acetonitrile indicated that even hydrophobic (non-polar) [BTA]-based ionic liquids were more polar than these organic solvents. 

I would like to thank the National Science Foundation for partial support of this work through Grant Number CPE81-15007. Special thanks to D. R. Lloyd for alerting me to some recent work on the use of solubility parameters in membrane research. 

They were the calculation of the Hildebrand solubility parameter as a function of density using tabulated thermodynamic data for carbon dioxide and Raman spectroscopy of test solutes dissolved in supercritical carbon dioxide compared to liquid solvents to evaluate solvent-solute interactions. The results of these recent approaches indicated that while the maximum solvent power of carbon dioxide is similar to that of hexane, probably somewhat higher, there is some solvent-solute interaction not found with hexane as the solvent. The limiting solvent power of carbon dioxide is resolved by choosing the alternative of a supercritical fluid mixture as the mobile phase. The component added to the supercritical fluid to increase its solvent power and/or to alter the chromatograph column is referred to as the "modifier."... 

Hansen has presented extensive tables with the solubility parameter increments (d,p,h). In his recent book, he has collected an extensive compilation of such values, van Krevelen proposed GC methods for all three increments according to the equations ... 

Polymer and solvent solubility parameters The most extensive compilation is provided in the recent book by Hansen and in the handbooks by Barton. - ... 

Vetere " proposed combining the FH equation (empirically modified to account for free-volume effects) with the NRTL expression for the energetic effects. The two NRTL parameters were correlated with the solubility parameters of the components. The relative importance of the combinatorial and residual contributions was analyzed and satisfactory results (for both VLB and LLE) are obtained for some binary systems, including aqueous polymer solutions. This recent approach is under development. 

The membrane conductivity of Nafion in various protic solvents has been measured in a recent study and the results are given in Table 12. The ratio of the membrane conductivity (k) to the solvent conductivity (k ) is listed in the last column of the table. A plot of the conductivity ratio (/solubility parameter of the solvent is shown in Fig. 22. The membrane conductivity is higher than the solvent conductivity in all solvents except formamide. 

The solubility parameter of Nafion membranes has been determined experimentally in a recent study (3) The samples which have been studied have an equivalent weight (EW) of either 1100 or 1200 (weight of polymer per sulfonic acid group). Since the samples are not soluble, the solubility parameter of the polymer can be determined only from the swelling technique (40 ... 

It is obvious that Nafion, in contrast to many other polymers, exhibits two solubility parameter values. This feature is uncommon for any other material whose solubility parameter has been reported (2). However, in a recent study (5) on radiation grafted membranes, it is reported that membranes consisting of sulfonic acid groups also show two solubility parameter values. 

In recent years, it has also become possible to obtain good estimates of the components of the solubility parameter from atomistic simulations, as illustrated by Goddard et al [20],... 

Recently, Bagley (4, 5) confirmed Hansen s approach by measuring directly the internal pressure of several solvents. The solubility parameters Bagley obtained corresponded closely to the sum of the dispersion and polar forces that Hansen proposed,... 

For the analysis of SN1 solvolyses, Abraham et al. (9) have proposed an equation (equation 3) based on sensitivities toward solvatochromatic properties. In equation 3, tr is a measure of solvent dipolarity-polarization, a is a measure of solvent hydrogen bond donor acidity, and P is a measure of solvent hydrogen bond acceptor basicity. More recently, a term governing cavity effects has been added, and this term is considered to represent an important contribution (10, 11). The cavity term can be directly related to the square of the Hildebrand solubility parameter (10-12). A similar analysis by Koppel and Palm (13, 14) involves terms governed by solvent polarity, solvent polarizability, electrophilic solvation ability, and nucleophilic solvation ability. Recently, a cavity term has also been added to this analysis (12). 

As for every material, the behavior of cellulose derivatives is governed by equations in which solubility parameters or surface free energy terms are frequently included. For comparison purposes, it seemed opportune to collect recently published data (Table 8). Polarity is for most applications a relevant parameter and therefore fractional polarities xp were calculated from solubility parameters or surface free energies, Eq. (4) Sect. 2.3. 

---