Si-Joong Kim

Bio: Si-Joong Kim is an academic researcher from University of South Carolina. The author has contributed to research in topics: Activity coefficient & Vapor pressure. The author has an hindex of 3, co-authored 3 publications receiving 36 citations.

Intermolecular association in structured liquids 1. Ethylene carbonate and N-methylacetamide

Abstract: Association constants of ethylene carbonate and N-methylacetamide have been calculated from measurements in dilute benzene solutions using a vapor pressure osmometer. The first association constants, K12, are 1.10 and 3.30 mol kg−1 respectively. The constants for subsequent association are 1.58 and 7.63 mol kg−1, respectively. The extension of these results to concentrated solutions using the isopiestic method indicates that pure liquid ethylene carbonate has an average of 8.3 monomer units per “cluster”. The chain length of N-methylacetamide increases to 8 or 9 units in 4 to 6 mol kg−1 solutions in benzene and then decreases due to steric interference. The average chain length appears to be about 4.8 units in the pure liquid.

Modeling of Activity Coefficients of Aqueous Solutions of Quaternary Ammonium Salts with the Electrolyte-NRTL Equation

Abstract: Ionic liquids (ILs) have been studied recently as potential “green” solvents because of their negligible vapor pressure. Modeling the phase behavior of such liquids with water and organic solvents and their partitioning between aqueous and organic phases is vital for an evaluation of their many potential uses. Unfortunately, phase behavior data for the popular imidazolium and pyridinium salts are still somewhat limited. However, a wealth of data exists for aqueous solutions of quaternary ammonium salts, a class of compounds that includes potentially interesting ILs. Therefore, as a first step toward modeling the phase behavior of IL solutions, we show how a conventional electrolyte model, the electrolyte nonrandom two-liquid (NRTL) model proposed by Chen et al. (AIChE J. 1982, 28, 588), can be applied to model activity coefficients of quaternary ammonium salts in water. This model requires two parameters per salt that must be fit to the experimental data. Particular attention is paid to computing these bi...

Vapor Pressures and Thermophysical Properties of Ethylene Carbonate, Propylene Carbonate, γ-Valerolactone, and γ-Butyrolactone

Abstract: In this work, a thermodynamic study of four important industrial solvents, ethylene carbonate (CAS RN: 96-49-1), propylene carbonate (CAS RN: 108-32-7), γ-valerolactone (CAS RN: 108-29-2), and γ-butyrolactone (CAS RN: 96-48-0), is presented. The vapor pressure measurements were performed by static method using two apparatuses in a combined temperature interval (238–363) K. Heat capacities of condensed phases were measured by Tian–Calvet calorimetry in the temperature interval (262–358) K. The phase behavior of ethylene carbonate and γ-valerolactone was investigated by a heat-flux DSC from 183–303 and 328 K, respectively. Ideal-gas thermodynamic properties were calculated using the methods of statistical thermodynamics based on calculated fundamental vibrational frequencies and molecular structure data. A consistent thermodynamic description of all involved properties (calculated ideal-gas heat capacities and experimental data on vapor pressures, condensed phase heat capacities, and vaporization enthalpies...

Recent progress on biodegradable tissue engineering scaffolds prepared by thermally-induced phase separation (TIPS)

Abstract: Porous biodegradable scaffolds provide a physical substrate for cells allowing them to attach, proliferate and guide the formation of new tissues. A variety of techniques have been developed to fabricate tissue engineering (TE) scaffolds, among them the most relevant is the thermally-induced phase separation (TIPS). This technique has been widely used in recent years to fabricate three-dimensional (3D) TE scaffolds. Low production cost, simple experimental procedure and easy processability together with the capability to produce highly porous scaffolds with controllable architecture justify the popularity of TIPS. This paper provides a general overview of the TIPS methodology applied for the preparation of 3D porous TE scaffolds. The recent advances in the fabrication of porous scaffolds through this technique, in terms of technology and material selection, have been reviewed. In addition, how properties can be effectively modified to serve as ideal substrates for specific target cells has been specifically addressed. Additionally, examples are offered with respect to changes of TIPS procedure parameters, the combination of TIPS with other techniques and innovations in polymer or filler selection.

Thermodynamics of binary mixtures containing N-alkylamides

Abstract: N -alkylamide + organic solvent mixtures have been investigated in the framework of a purely physical theory [ dis persive- qua si c hemical (DISQUAC)]. The amides considered are n -methylformamide (NMF), n -methylacetamide (NMA), n -ethylacetamide (NEA), n -methylpropanamide (NMPA), 2-pyrrolidone and caprolactam. The solvents are alkanes, benzene, toluene or 1-alkanols. The DISQUAC interaction parameters are reported. The model describes consistently thermodynamic properties such as vapor–liquid equilibria (VLE), excess molar Gibbs energies, G E , and excess molar enthalpies, H E , solid–liquid equilibria (SLE), or the concentration–concentration structure factor, S CC (0). DISQUAC improves results from other models, such as the e xtended r eal a ssociated s olution model (ERAS) or UNIFAC. Interactions present in the studied mixtures are discussed. Solutions with alkanes are characterized by strong dipole–dipole interactions between amide molecules. n -Methylformamide+aromatic compound mixtures behave similarly to associated systems. The heterocoordination observed in some solutions involving methanol where interactions between like molecules are almost cancelled by interactions between unlike molecules may partially be ascribed to size effects. For other alcoholic solutions, the ability of the alcohol for the breakage of the amide–amide interactions is prevalent over solvation effects.

Water activity data representation of aqueous solutions at 25°C

Abstract: Polynomial expressions have been fitted to the complete range of available water-activity data for 396 electrolyte and non-electrolyte aqueous binary systems. The standard deviation of regression rarely exceeded 0.001 and was less than 0.0002 in most cases. Such data representation is useful for the prediction of the water-activity of mixed moderately concentrated aqueous solutions. La representation de la gamme complete des donnees de l'activite de l'eau pour 396 systemes binaires aqueux comprenant des electrolytes et des non-electrolytes a ete effectuee par des expressions polynomiales. Celles-ci donnent une deviation standard qui depasse rarement 0.001 et qui est inferieure a 0.0002 dans la plupart des cas. Ce mode de representation s'avere ětre utile a l'estimation de l'activite de l'eau de solutions aqueuses mixtes moderement concentrees.