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Compressed CO2 (compressed + co2)

Distribution by Scientific Domains

Polymers and Materials Science	60%

Selected Abstracts

Enhanced Stabilization of Reverse Micelles by Compressed CO2

CHEMISTRY - A EUROPEAN JOURNAL, Issue 4 2005
Dong Shen Dr.
Abstract The effect of compressed CO2 on the solubilization capacity of water in reverse micelles of sodium bis(2-ethylhexyl) sulfosuccinate (AOT) in longer chain n -alkanes was studied at different temperatures and pressures. It was found that the amount of solubilized water is increased considerably by CO2 in a suitable pressure range. The suitable CO2 pressure range in which the solubilization capacity of water could be enhanced decreased with increasing W0 (water-to-AOT molar ratio). The microenvironments in the CO2 -stabilized reverse micelles were investigated by UV/Vis adsorption spectroscopy with methyl orange (MO) as probe. The mechanism by which the reverse micelles are stabilized by CO2 is discussed in detail. The main reason is likely to be that CO2 has a much smaller molecular volume than the n -alkane solvents studied in this work. Therefore, it can penetrate the interfacial film of the reverse micelles and stabilize them by increasing the rigidity of the micellar interface and thus reducing the attractive interaction between the droplets. However, if the CO2 pressure is too high, the solvent strength of the solvents is reduced markedly, and this induces phase separation in the micellar solution. [source]

Continuous, Atmospheric Process to Create Organic Clusters and Nanostructured, Functional Films,

ADVANCED FUNCTIONAL MATERIALS, Issue 5 2006
R. Jagannathan
Abstract An atmospheric process based on compressed CO2 is used to create stable clusters of small organic molecules. These clusters, 1,10,nm in size, are used as building blocks to assemble thin films on various substrates. Cluster assembly of these films is verified by using low-angle X-ray diffraction. The surface quality of these cluster-assembled films is similar to that of films usually prepared via the vacuum process. Several functional organic light-emitting diode devices have been prepared, in which only the doped emissive layer has been deposited by our process. The radiometric features and efficiencies of these devices match those of vacuum-built devices. Atomic force microscopy of these molecular clusters reveals that they are liquid-like at standard atmospheric conditions. Coatings of these clusters on cloth and stainless steel have been found to be superhydrophobic in nature. [source]

Synthesis of gradient copolymers with complexing groups by RAFT polymerization and their solubility in supercritical CO2

JOURNAL OF POLYMER SCIENCE (IN TWO SECTIONS), Issue 20 2009
Tiphaine Ribaut
Abstract We report the synthesis of new gradient fluorinated copolymers with complexing groups and soluble in supercritical carbon dioxide (scCO2). Poly(1,1,2,2-tetrahydroperfluorodecyl acrylate- co -acetoacetoxyethyl methacrylate) (poly(FDA- co -AAEM)) and poly(1,1,2,2-tetrahydroperfluorodecyl acrylate- co -vinylbenzylphosphonic acid diethylester) (poly(FDA- co -VBPDE)) gradient copolymers were synthesized by reversible addition fragmentation chain transfer polymerization in ,,,,,-trifluorotoluene. Poly(1,1,2,2-tetrahydroperfluorodecyl acrylate- co -vinylbenzylphosphonic diacid) (poly(FDA- co -VBPDA)) gradient copolymer was efficiently obtained by cleavage of the phosphonic ester groups of poly(FDA- co -VBPDE). The cloud points of these gradient copolymers in dense CO2 were measured in a variable volume view cell at temperatures between 25 and 65 °C. The gradient copolymers show very good solubility in compressed CO2 with the decreasing order: poly(FDA- co -AAEM) , poly(FDA- co -VBPDE) > poly(FDA- co -VBPDA). Following a green chemistry strategy, poly(FDA- co -AAEM) gradient copolymer was successfully synthesized in scCO2 with a good control over number-average molecular weight and composition. © 2009 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 47: 5448,5460, 2009 [source]

Thermal behaviors of polystyrene plasticized with compressed carbon dioxide in a sealed system

POLYMER ENGINEERING & SCIENCE, Issue 9 2009
Long Yu
The thermal behavior of polystyrene (PS) plasticized with compressed carbon dioxide (CO2) was studied using differential scanning calorimetry with a high-pressure stainless steel pan in a sealed system. The technique proved to be a simple and convenient way to study the thermal behavior of a polymer plasticized with compressed CO2 at pressures up to 100 atm, which covers both the gas and supercritical states. A sharp fall in the decrease rate of the glass transition temperature (Tg) under conditions near the critical point of compressed CO2 was firstly observed, which corresponded with the solubility of CO2 in PS. Since the system is scaled, which results in a stable pressure at a certain temperature, it is more suitable to study the effect of annealing. An endotherm was detected after the PS was annealed at a temperature below its Tg under compressed CO2. The enthalpy of this endotherm increased linearly with increasing logarithm of annealing time under a certain pressure. The endotherm was affected by two thermodynamic equilibrations at a temperature below its Tg: (i) enthalpy relaxation of the PS; and (ii) the absorption/desorption of CO2. POLYM. ENG. SCI., 2009. © 2009 Society of Plastics Engineers [source]