Direct measurement and calculation of the second refractivity virial coefficients of gases

Burns, Robert C.; Graham, C. D.; Weller, A.R.M.

doi:10.1080/00268978600101901

Cited by 90 publications

(35 citation statements)

References 48 publications

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“…Accordingly, when the dispersed particles are much smaller than the sizes of the pores, they might be only partially bonded to the pore walls. [38] and any effect from the stiff surroundings cannot take place. However, when the particle size is large enough, the silica matrix would exert a great effect on the enclosed particles, [39] the large A 132 at lower pressure of CO 2 explains this phenomenon well.…”

Section: Resultsmentioning

confidence: 98%

In situ Synthesis of Gold Nanoparticles inside the Pores of MCM‐48 in Supercritical Carbon Dioxide and its Catalytic Application

et al. 2006

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Gold nanoparticles are deposited into the channels of MCM-48 through a simple H 2 -assisted reduction of HAuCl 4 (aqueous solution) in supercritical carbon dioxide medium at 70 8C within 2-4 h. The nanoparticles were characterized by powder Xray diffraction (PXRD), N 2 adsorption-desorption, transmission electron microscopy (TEM), and UVVis spectroscopy. The particle size of the synthesized material is tunable with the pressure (density) of the supercritical carbon dioxide medium. At the fixed temperature (70 8C) and hydrogen pressure [P(H 2 ) = 2 MPa], the Au particle size varies from ca. 25 nm to ca. 2 nm with the change in CO 2 pressure from 7 MPa to 17 MPa. At the low solvent density conditions, larger particles of~25 nm were obtained. On the contrary, a high solvent density of CO 2 slows down particle aggregation, resulting in the small particle size within the range of 2-5 nm. This change in particle size with CO 2 pressure and the interaction of the particles with the silica support were correlated well with long-range van der Waals interactions and consequently the Hamaker constant for the gold nanoparticle-CO 2 (A 131 ) and silica-gold core-CO 2 (A 132 ), respectively. Supercritical carbon dioxide alone can provide a unique environment for stabilizing gold nanoparticles in the channels of the cubic mesoporous MCM-48 support and exquisite control of the particle size without perturbing the support structure. The synthesized material is highly stable, recyclable and no metal nanoparticle leaching was observed. The selective hydrogenation of crotonaldehyde with the synthesized material provides convincing evidence that the particles are inside the pores and available to the reactant molecules.

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Section: Resultsmentioning

confidence: 98%

In situ Synthesis of Gold Nanoparticles inside the Pores of MCM‐48 in Supercritical Carbon Dioxide and its Catalytic Application

et al. 2006

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“…The refractive 14,15 index was calculated from the virial equation for the molar refractivity of the carbon dioxide at 45°C…”

Section: Static Light Scatteringmentioning

confidence: 99%

Light-Scattering Study of Diblock Copolymers in Supercritical Carbon Dioxide: CO₂ Density-Induced Micellization Transition

et al. 1998

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The behavior of polymeric surfactant polyvinyl acetate (PVAC)-b-poly(1,1,2,2-tetrahydroperfluorooctyl acrylate) (PTAN) in supercritical carbon dioxide (CO2) was investigated using static and dynamic light scattering. We observed three regions on the phase diagram of the copolymer in supercritical CO2: (i) two-phase region at low CO2 density; (ii) solutions of spherical micelles at intermediate CO2 densities; (iii) solutions of unimers (individual copolymer chains) at high CO2 densities. The aggregation number (the number of copolymer chains in a micelle) decreases with an increasing density of supercritical CO2 in region (ii). An increase of the CO2 density corresponds to the improvement of solvent quality for both blocks of the copolymer (PVAC and PTAN). The hydrodynamic radius of micelles and unimers was measured using dynamic light scattering in regions (ii) and (iii), respectively. This light-scattering study is the first one reporting a solvent density-induced transition between spherical micelles at lower supercritical CO 2 density and unimers at higher CO2 density. The light-scattering technique appears to be a very powerful tool for the analysis of the carbon dioxide density-induced micellization transition. This phenomenon is unique to supercritical fluids and demonstrates a convenient control over the polymer solubility.

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“…For the data analysis, the refractive index and viscosity values for CO 2 were taken from Burns et al 38 and Fenghour et al, 39 respectively. At 400 bar and 25°C, these are 1.245 and 0.13 cP.…”

Section: Methodsmentioning

confidence: 99%

Block Copolymer Vesicles in Liquid CO₂

2007

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Two polylactide-b-poly(perfluoropropylene oxide) (PLA-PFPO) diblock copolymers were synthesized via a coupling reaction of acid chloride end-functionalized poly(perfluoropropylene oxide) and hydroxyterminated polylactide. The solubility of these materials in CO 2 was measured using a variable-volume highpressure cell. At a concentration of 1 wt %, the PLA-PFPO copolymers were found to be soluble at modest pressures (<500 bar) over the temperature range of 30-65°C. The size of the resulting micelles in solution was characterized by high-pressure dynamic light scattering. These measurements indicated the formation of predominantly small, spherical micelles for the block copolymer with a PFPO volume fraction of 0.49 and large aggregates with hydrodynamic radii of 100 nm for PLA-PFPO with a PFPO volume fraction of 0.37. By kinetically trapping the aggregates in CO 2 through vitrification of the PLA cores, redispersing them in an analogous PFPO selective solvent, and imaging them using transmission electron microscopy, we confirmed the formation of block copolymer vesicles in liquid CO 2 .

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Direct measurement and calculation of the second refractivity virial coefficients of gases

Cited by 90 publications

References 48 publications

In situ Synthesis of Gold Nanoparticles inside the Pores of MCM‐48 in Supercritical Carbon Dioxide and its Catalytic Application

In situ Synthesis of Gold Nanoparticles inside the Pores of MCM‐48 in Supercritical Carbon Dioxide and its Catalytic Application

Light-Scattering Study of Diblock Copolymers in Supercritical Carbon Dioxide: CO₂ Density-Induced Micellization Transition

Block Copolymer Vesicles in Liquid CO₂

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Direct measurement and calculation of the second refractivity virial coefficients of gases

Cited by 90 publications

References 48 publications

In situ Synthesis of Gold Nanoparticles inside the Pores of MCM‐48 in Supercritical Carbon Dioxide and its Catalytic Application

In situ Synthesis of Gold Nanoparticles inside the Pores of MCM‐48 in Supercritical Carbon Dioxide and its Catalytic Application

Light-Scattering Study of Diblock Copolymers in Supercritical Carbon Dioxide: CO2 Density-Induced Micellization Transition

Block Copolymer Vesicles in Liquid CO2

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Product

Resources

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Light-Scattering Study of Diblock Copolymers in Supercritical Carbon Dioxide: CO₂ Density-Induced Micellization Transition

Block Copolymer Vesicles in Liquid CO₂