Biomedical subjects

Tiancheng Mu

Publications and source records attributed to Tiancheng Mu.

3 recordsLinked to original sources

PubMed2005

Compressed CO2 in AOT reverse micellar solution: effect on stability, percolation, and size.

The effects of compressed CO(2) in sodium bis-2-ethylhexylsulfosuccinate (AOT)/decane reversed micellar solution on the stability of the micelles, interface, and micelle/micelle interactions were studied. It was demonstrated that the compressed gas could increase the solubilization of water in this system. The formation of the stabilized one-phase microemulsion was confirmed by conductivity measurements. A shift in percolation threshold to higher temperature was observed after compressed gas was added. The gyration radius (R(g)) of the reverse micelles was determined using SAXS. R(g) increases with the addition of water, while it decreases appreciably with increasing pressure of compressed gas at fixed W(0). These results were interpreted in terms of an increase of the rigidity of the interface layer and a decrease of the interdroplet attraction. The results of this work provide useful information to get insight into the mechanism of cosurfactants to stabilize reverse micelles.

Journal Article↗

PubMed2004

Enthalpy of solution of 1,4-naphthoquinone in CO2 + n-pentane in the critical region of the binary mixture: mechanism of solubility enhancement.

The enthalpy of solution (Delta(solv)H(m)) and solubility of 1,4-naphthoquinone in CO(2) + n-pentane were measured at 308.15 K in the critical region of the binary fluid. In order to study the effect of phase behavior of the mixed solvent on Delta(solv)H(m), the experiments were carried out in the supercritical (SC) and subcritical region of the binary solvent. The density of the mixed solvent in different conditions was determined. The isothermal compressibility (K(T)) of the mixed solvent, and the partial molar volume (V(n-pentane)) of n-pentane in the solution were calculated. It was demonstrated that the Delta(solv)H(m) was negative in all conditions. Delta(solv)H(m) is nearly independent of pressure or density in all the solvents in a high-density region, in which compressibility of the solvent is very small; this indicates that the intermolecular interaction between the solvent and the solute is similar to that for liquid solutions. It is very interesting that Delta(solv)H(m) in the mixed SC fluid differs from the Delta(solv)H(m) in mixed subcritical fluids. The absolute value of Delta(solv)H(m) in the mixed SC fluid is close to that in pure SC CO(2) in the high-density region, and is much lower than that in pure SC CO(2) in the low-density region. In the mixed subcritical fluids, the Delta(solv)H(m) is also close to that in the pure CO(2) in the high-density region. However, at the same density, the absolute value of Delta(solv)H(m) in the binary subcritical fluid is larger than that in pure CO(2) in the high-compressible region of the mixed solvent. The main reason for this is that the degree of clustering in the SC solutions is small at the density in which the degree of clustering is large in the subcritical solutions. It can be concluded that solubility enhancement by n-pentane in the mixed SC fluid is entropy driven. In contrast, the solubility enhancement by n-pentane in subcritical fluids is enthalpy driven. The intermolecular interaction in the SC solutions and subcritical solutions can be significantly different even if their densities are the same.

Carbon Dioxide↗

PubMed2004

Tautomeric equilibrium of ethyl acetoacetate in compressed CO2 + ethanol and CO2 + methanol mixtures.

Tautomerism equilibrium of ethyl acetoacetate (EAA) in compressed CO2 + methanol and CO2 + ethanol mixtures was studied by UV-Vis spectroscopy at 308.15 K and different pressures. The volume expansion coefficient (alpha) of the solvents at different pressures was also determined. The relative permittivity (epsilon) of CO2 + methanol and CO2 + ethanol mixtures at different conditions was calculated using the Kc and Onsager solvent parameter. The equilibrium constant (Kc) of EAA in the binary mixtures increases considerably with increasing pressure or volume expansion coefficient. The relative permittivity or the polarity of the binary mixtures decreases sharply with increasing volume expansion coefficient in the range of 0 < alpha < 1.5. However, as the volume expansion coefficient exceeds 1.5, the relative permittivity decreases slowly. In other words, the dissolution of CO2 in the polar solvents can reduce the polarity of the solvents significantly in the low volume expansion coefficient range, and the polarity of the solution is not sensitive to the volume expansion coefficient as its value is large enough. The difference in polarity of the two solvents reduces with increasing pressure and becomes negligible after volume expansion coefficient exceeds about 2.5.

Acetoacetates↗