Isothermal compressibility, model interactions

Two characteristics of liquid water that are relevant to the present answer are the equation of state characteristics shown in Figs. 8.11 and 8.12. The isothermal compressibilities shown in Fig. 8.11 indicate that water is stiffer than organic solvents, and that the stiffness is only weakly temperature-dependent. We don t propose here a detailed explanation of that stiffness - it is due to intermolecular interactions among solvent molecules, hydrogen bonding in the case of liquid water (Debenedetti, 2003) - but the present empirical theory of hydrophobicity merely exploits those results. This stiffness is the principal determinant of the low solubility of inert gases in liquid water. In the simplest information models this stiffness, and its temperature dependence, is expressed by the experimental n (n — l))o, which is distinctive of liquid water. 

Despite the referred advantages, the modeling of mechanical partial molecular properties of solutes at infinite dilution is intrinsically problematic, that is, they scale as the solvent isothermal compressibility (Levelt Sengers 1991), with finite prefactors associated with the magnitude of the molecular solute-solvent interaction asymmetry (Chialvo and Cummings 1995) as we will illustrate below. However, in an effort to facilitate the regression of experimental data. Wood and coworkers (Sedlbauer, Yezdimer, and Wood 1998) and O Connell and cowoikers (O Connell,... 

For a molten, immiscible, binary blend of polymers A and B, Helfand et al developed a quantitative lattice theory of the interphase [4-6]. The model assumed that interactions between statistical segments of pol)nners A and B are determined by x 12 the isothermal compressibility is negligible, and there is no volume change upon blending. The segmental density profile, p/ where i = 1 or 2, was solved for infinitely long... 

The four possible stereomers of a chiral surfactant with two asymmetric centers within the polar head group have been synthesized and their absolute configuration determined by X-ray diffraction. One of the diastereomers exhibits a chiral discrimination when spread on water interface the monolayer racemic film undergoes a phase transition from a liquid-expanded towards a liquid-condensed phase upon compression, while the pure enantiomers only have a liquid-expanded phase, as revealed by the measured pressure-area isotherms. The transition pressure-composition diagram indicates that heterochiral interactions are favored. Our results are compared to predictions of Andelman and de Gennes based upon a statistical model. 

---