Solution, athermal thermodynamics

Some typical results are shown in Figure 16.2 (LLE for PS/acetone), Table 16.4 (infinite dilution activity coefficient for PBMA solutions in a variety of solvents). Tables 16.5 and 16.6 (activity coefficients of low- and heavy-molecular-weight alkanes in asymmetric athermal-alkane solutions). Table 16.7 (VLB for ternary polymer-solvent solutions). Figure 16.6 (VLB calculations for systems containing the commercial epoxy resin Araldit), and Table 16.8 (comparison of LLE results from various thermodynamic models). 

Athermal solution, 184 Auxiliary operations, 3 Availability function, 685 Azeotropes, distillation, 9 hetoogeneous, 101 homogeneous, 101 maximum-boiling, 99,208-209 minimum-boiling, 98,100,207-208 thermodynamic activity coefficients, 208 Azeotropic distillation, 9,13... 

Hildebrand and Rotariu [14] have considered differences in heat content, entro])v and activity and classified solutions as ideal, regular, athermal, associated and solvated. Despite much fundamental work the theory of binary liquid mixtures is still e.ssentiaUy unsatisfactory as can be seen from the. systematic treatment of binar> mi.Ktures by Mauser-Kortiim [15]. The thermodynamics of mixtures is presented most instructively in the books of Mannchen [16] and Schuberth [17]. Bittrich et al. [17a] give an account of model calculations concerning thermophysical properties of juire and mixed fluids. 

Since polymer solutions in principle do not fulfill the rules of the ideal mixture but show strong negative deviations from Raoult s law due to the difference in molecular size, the athermal Flory-Huggins mixture is usually applied as the reference mixture within polymer solution thermodynamics. Starting from Equation [4.4.11] or from... 

In dilute solutions, the single polymer coil expands in the athermal solvent. In a good solvent, the coil will expand more significantly. In contrast, in a poor solvent, the chain units and the solvent undergo a phase separatiOTi under a proper thermodynamic condition. Consequently, the single chain will collapse drastically into a condensed sphere. Therefore, the internal concentration reaches... 

This simple model accommodates the existence of rod-like structures needed for liquid crystal formation, without recourse to anisotropy of individual molecules. The secretions are biphasic (mixed isotropic/liquid crystalline) over a narrow concentration range implying that they have the thermodynamic characteristics typical of an athermal liquid crystalline solution (Figure 12.10). 

These solutions exhibit also a partially ideal behaviour and have specific thermodynamic properties. The excess functions, represented by the enthalpy of mixing and the excess quantities derived from it, are zero and justify considering these solutions as being almost ideal. Thus, the athermal solutions fulfil the following group of major conditions ... 

The systematic study of athermal solutions was initiated by Fowler and Eushbrooke [40] who proposed the lattice model as the only one capable of providing the quantitative and explicit formulas for thermodynamic quantities, proving at the same time that, in contrast to previous assumptions, the athermal mixtures are not ideal. The entropy of mixing of these systems is not ideal. 

Flory s theory developed for athermal polymer solutions leads to much simpler expressions of thermodynamic functions, the only variable being the volume fraction of the polymer [48—50]. 

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