Relativistic state equations for the interface

Relativistic state equations were obtained for various interfaces and cases. The relativistic state equation was done for perfect gases as well.     

New volume translation for cubic equations of state

Peneloux's volume translation is found of not equal benefit depending on pressure and temperature ranges for which volumetric properties are represented (some ranges being unfortunately worse described after correction than before).     

Empirical equations of state for adsorption layer: Alkylthiopolyoxyethylene glycols

Surface tension isotherms ofn-alkylthiopolyoxyerhylene glycols:n-C _x H_2x+1S(CH₂CH₂O) _y H, wherex=5 to 8,y=3 or 4, were approximated with orthogonal polynomials to get good quality values of surface pressure (II) and molar area of the adsorbed layer (). The modified Volmer (*(–₀)=Z*R*T) van der Waals and virial equations of state were used to correlate and in terms of real two-dimensional gas. The combination of Volmer and van der Waals equations of state made it possible to determine the interaction energy, , which was prescribed to cohesion of hydrophobic chains in the adsorption layer. The value of for the amphiphiles in question was in the range 0.97–1.91R*T and the average contribution per methylene group was ca. 0.21R*T.The Lennard-Jones potentials calculated from second virial coefficient were of the same range as , but no clear relation was found between their values and number of structure elements of the alkylthiopolyoxyethlene glycols.Presented during 7th International Conference: Surface and Colloid Science, July 7–13, 1991, Compiegne, France     

Cubic equations of state for adsorption layer: alkylthiopolyoxyethylene glycols

The van der Waals, Redlich-Kwong, Peng-Robinson and an equation of state derived by Smith were applied to approximate the run of surface pressure () — area () curves of the adsorption layer ofn-pentyl ton-octyl thioethers of tri- and tetraoxyethylene glycols. The equation parameters: excluded molar area (_oi) and an interaction energy term (a _i) were determined by simplex method for values in the range of 2–23.5 mN/m. The equations parameters were found to be related to the structure of the amphiphile. The _oi decreased with the length of hydrocarbon thioether chain and was nearly uniform for equations of state in question except for Smith equation. The value ofa _i was dependent on the amphiphile structure. It was used to obtain the interaction energy _i between amphiphiles in the adsorption layer. The values of _i determined as an increment per methylene group was in the range of ca. 0.2–0.32R*T, depending on the equation of state used.     

Alkyl-modified siloxanes as pseudostationary phases for electrokinetic chromatography

Anionic siloxane polymers with novel linker arm structures have been synthesized and characterized with respect to their performance and selectivity as pseudophases for electrokinetic chromatography. The linker arm between the siloxane backbone and the sulfonate head group is shorter and does not have the tertiary amine structure found in the siloxane pseudophases studied previously. This change in the linker arm structure and chemistry has dramatic effects on the chemical selectivity of the pseudophases. Linear solvation energy relationship (LSER) studies show that the greatest contributor to the difference in selectivity is that the new polymers are not as nonpolar as those previously studied. This result indicates that siloxane polymers are not by their nature more nonpolar or hydrophobic than other pseudophases. The LSER studies also demonstrate that siloxane pseudophases have a strong tendency to accept hydrogen bonds that cannot be attributed to the presence of the tertiary amine in the linker arm.     

Benzoxazine siloxanes as modifiers of epoxy resins for coatings

Coatings based on epoxy resin ED-20 modified with organosilicon 1,3-benzoxazines at a concentration of 1–10 wt % have been prepared and studied. According to the DSC data, the curing temperature of the modified compositions falls in the range of 130–150°C. It has been shown that the use of benzoxazine siloxanes as modifying additives significantly improves the adhesion and anticorrosive properties of epoxy coatings.     

Thermodynamic equations of state from molecular solvation

A general expression of the canonical partition function for mixture fluids in terms of solvation free energy is presented. Following the same approach as set forth in generalized van der Waals theory, we show that the physical assumptions made in existing thermodynamic models from the perspective of molecular solvation can be prevailed. For example, the temperature dependence on the coordination number, i.e. the number of solvent molecules surrounding the solute, has an impact not only on the temperature dependence of the solvation free energy but on the non-linear solvent reaction field response as well. More importantly, the new formulation provides a unified scheme for deriving the commonly used equations of state (EOS) and newly developed COSMO-type liquid activity coefficient models. We show that from this new formulation it is possible to develop a new class of thermodynamic models that behave like existing EOS and liquid models in the low and high-density limits, respectively.     

Fluid phase stability and equations of state

Many textbook explanations of fluid-phase stability and phase splitting are based on the assumption that the Gibbs energy of the mixture is a smooth, continuous function of composition that exhibits inflection points and a maximum. The true function, rather, is composed of branches which may not have inflection points and which typically meet at a cusp. Examples of these curves are shown and explained.     

Boyle temperature and cubic equations of state

The sensitivity of Boyle temperature to changes in parameters appearing in cubic equations of state and to volume shift is analyzed. Analytical expressions for the Boyle temperature and for the dependency to the shift of the equation of state are given for the most common cases of the alpha function.     

Accurate thermodynamic and dielectric equations of state for high-temperature simulated water

The thermodynamic and dielectric properties of the simple point charge extended (SPC/E) water model are examined over wide temperature and density range by means of molecular dynamic simulations. Accurate analytical thermodynamic and dielectric equations of state for the SPC/E pair-potential are presented. Parameterizations cover a broad range of high temperature states including the critical region. The critical point parameters of SPC/E water were determined to be ρ_c = 0.276 g/cm³, T_c = 640.25 K and p_c = 164.37 bar. The value of the static dielectric constant of SPC/E water at its critical point was calculated to be 5.35, which compares remarkably well with the corresponding experimental value of 5.36. Analytical thermodynamic and dielectric equations for the saturated liquid and vapor densities are also given.     

Performance of equations of state for additive hard-disk fluid mixtures for extreme diameter ratios

Monte Carlo computer simulations have been performed for additive hard-disk fluid mixtures with diameter ratios R = 5 and 10. These data are used to analyze the performance of several theoretically based equations of state proposed in the literature for that kind of mixtures.