Alcohols, solubility parameter

As may be expected of an amorphous polymer in the middle range of the solubility parameter table, poly(methyl methacrylate) is soluble in a number of solvents with similar solubility parameters. Some examples were given in the previous section. The polymer is attacked by mineral acids but is resistant to alkalis, water and most aqueous inorganic salt solutions. A number of organic materials although not solvents may cause crazing and cracking, e.g. aliphatic alcohols. 

The solubility parameter is about 19.2MPa and being amorphous they dissolve in such solvents as tetrahydrofuran, mesityl oxide, diacetone alcohol and dioxane. Since the main chain is composed of stable C—C and C—O—C linkages the polymer is relatively stable to chemical attack, particularly from acids and alkalis. As already mentioned, the pendant hydroxyl groups are reactive and provide a site for cross-linking. 

Paine et al. [85] extensively studied the effect of solvent in the dispersion polymerization of styrene in the polar media. In their study, the dispersion polymerization of styrene was carried out by changing the dispersion medium. They used hydroxypropyl cellulose (HPC) as the stabilizer and its concentration was fixed to 1.5% within a series of -alcohols tried as the dispersion media. The particle size increased from only 2.0 /itm in methanol to about 8.3 /itm in pentanol, and then decreased back to 1 ixm in octadecanol. The particle size values plotted against the Hansen solubility parameters... 

Figure 13 The variation of particle size with the Hansen solubility parameter of the n-alcohols. (Adapted from Ref. 85 with the permission of John Wiley Sons, Inc.)...

Another important use of solubility parameters is in interpreting the effects of different solvents on the rates of reactions. In a chemical reaction, it is the concentration of the transition state that determines the rate of the reaction. Depending on the characteristics of the transition state, the solvent used can either facilitate or hinder its formation. For example, a transition state that is large and has little charge separation is hindered in its formation by using a solvent that has a high value of S. The volume of activation is usually positive for forming such a transition state which requires expansion of the solvent. A reaction of this type is the esterification of acetic anhydride with ethyl alcohol ... 

Figure 7.2 The relationship between the solubility parameter (8), and the relative rates for the reaction shown in Scheme 7.4. (Note that 8 for trifluoroethanol did not appear in the original publication [10] and was estimated by correlating it for other alcohols)...

The parameter for the interaction between the oil and the tails Xos is expressed in terms of the solubility parameters <5g, dA, and of the surfactant tail, the alcohol tail and... 

Example 7.3 Estimate the solubility parameter components of diacetone alcohol OH... 

Estimate the solubility parameter and its components of diacetone alcohol,... 

Here d refers to the solubility parameter of copper(II) decanoate dim denotes the dimerization constant of Cu(II) decanoate in an ideal solution and n represents the number of solvent molecules set free in the dimerization of Cu(II) decanoate, that is, nV0 = 2VCuA2 — VCll2A4, where VCuA2 and VCU2A4 indicate the molar volume of the solvated monomeric and dimeric Cu(II) decanoates. CuA2 and Cu2A4 are assumed to have the same solubility parameter (141), and d was found to be 24.1 (Jin cm 3/2) (151). The plot of (log dim — log VB) against 0.43 Vo(<50 — S )2/RT was remarkably linear (15./,153). From this plot the values of n and log dim were found to be 4.5 and 3.14 for alcohols, and 2.8 and 3.19 for ketones by the least-squares method. From these results they concluded that, because of extensive solvation, the monomeric copper(II) decanoate is more stabilized in alcohols than in ketones. 

Certain amino-functional actives form water-insoluble complexes with carbomer often this can be prevented by adjusting the solubility parameter of the fluid phase using appropriate alcohols and polyols. 

The order (1,4-dioxane > alcohol > hydrocarbon) is in agreement with the data reported by Mohlin and Gray (16). The solubility parameters (MPa) of cellulose and the organic vapors studied are ... 

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. 

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