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The cloud-point pressure of poly(t-butylaminoethyl methacrylate) [Poly(TBAEMA)] in various solvents such as supercritical carbon dioxide (CO2), dimethyl ether (DME) and t-butylaminoethyl methacrylate (TBAEMA) was measured to maximum pressure and temperature of 218.79MPa and 452.9 K, respectively. The phase behavior for the Poly(TBAEMA)+CO2+TBAEMA mixture was investigated according to the various contribution factors, such as pressure, temperature and concentration with TBAEMA mass fraction of 9.9 wt%, 10.4 wt%, 14.9 wt%, 24.4 wt% and 35.2 wt%. The cloud point curves for the Poly(TBAEMA)+CO2+DME (15.6-78.7 wt%) systems show the variation of the (p, T) curve from upper critical solution temperature (UCST) region to lower critical solution temperature (LCST) region as DME concentration increases. The experimental data for the CO2+TBAEMA system were reported at the broad temperature range of 313.2 K to 393.2 K and the pressure range of 3.70MPa to 20.62MPa. The CO2+TBAEMA binary system shows the type-I phase behavior with a continuous critical mixture curve, and is correlated by Peng-Robinson equation of state with the critical properties for TBAEMA obtained by Joback and Lyderson group contribution method.

Perturbed-chain statistical associating fluid theory (PC-SAFT) was applied for modeling the thermodynamic properties of aqueous amino acid solutions. To account for the association phenomena of amino acids occurring in the aqueous solution, the zwitterionic forms of amino acids are assumed to be associating species with proton donor and acceptor sites. Also, in order to reduce the number of adjustable parameters of PC-SAFT equation of state (EoS) for amino acids from five to three, it is assumed that segment numbers of amino acids are linearly related with the molecular weight of amino acids, and the association volume parameters of amino acids can be set to a fixed value. Thus, 3-parameters of PC-SAFT EoS for amino acids were estimated by simultaneously fitting the activity coefficients of amino acid and densities data in the aqueous amino acid solutions. The PC-SAFT EoS with estimated 3-parameters of amino acid is found to well describe activity coefficients of amino acid and densities of the aqueous amino acid solutions. Also, this equation was used for predicting solubilities of amino acids as well as the water activities and osmotic coefficients in the aqueous amino acid solutions. The predicted values of these properties are in good agreement with the experimental data.

In this work an equation of state applicable to the system containing electrolytes has been developed by coupling the perturbed chain statistical associating fluid theory (PC-SAFT) with the primitive mean spherical approximation. The resulting electrolyte equation of state is characterized by 4 ion parameters for each of the cation and anion contained in aqueous solutions, and 4 ion specific parameters for each of six cations (Li+, Na+, K+, Rb+, Mg2+ and Ca2+) and six anions (Cl−, Br−, I−, HCO 3 − , NO 3 − and SO 4 2− ) were estimated, based upon the individual ion approach, from the fitting of experimental densities and mean ionic activity coefficients of 26 aqueous single-salt solutions at 298.15 K and 1 bar. The present equation of state with the estimated individual ion parameters has been found to satisfactorily describe not only the densities and mean ionic activity coefficients, but also osmotic coefficients and water activities of single-salt aqueous solutions. Furthermore, the present model was extended to two-salt aqueous solutions, and it has been found that thermodynamic properties such as mentioned above, of two-salt solutions, can be well predicted with the present model, without any additional adjustable parameters.

For developing the equation of state which can be applicable to associating fluids, the Perturbed-Hard-Sphere-Chain-Association (PHSC-AS) equation of state is proposed by incorporating the association term of the SAFT model into the PHSC equation of state which has been widely used to describe phase equilibria for the fluid system containing a large molecule such as polymer. In this work, two different types of PHSC models have been examined. One is the original model proposed by Song et al., and the other is the modified model by Kim and Bae whose chain term was replaced with that of the SAFT model. As a result, two types of PHSC-AS models are obtained, and applied to the calculation of phase equilibria for the binary system containing a self-associating compound such as alcohol, amine and carboxylic acid, etc. The calculated results of vapour-liquid equilibria are in good agreement with the experimental data. The proposed models (PHSC-AS) are also compared to the PC-SAFT model.