Design of Nonionic Surfactants for Supercritical Carbon Dioxide

McClain, J. B.; Betts, Douglas E.; Canelas, Dorian A.; Samulski, Edward T.; DeSimone, Joseph M.; Londono, J. D.; Cochran, H. D.; Wígnall, G. D.; Martino, Delia Chillura; Triolo, R.

doi:10.1126/science.274.5295.2049

Cited by 270 publications

(233 citation statements)

References 23 publications

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“…3c-e,f,g, 8 We may estimate the ratio of (Q ) 0) cross sections shown in Figure 3 (from eq 1) 11 as 5.2 ( 0.7, assuming that the surfactant layer is "invisible" (F 2 ≈ F s ), and the scattering arises mainly from the D 2 O core. While the calculated (5.2) and experimental (1.58/0.43 ) 3.7) ratios are similar, we believe that the difference is outside the experimental error and that this arises from the neglect of interparticle interactions 12,13 and also the smaller, but finite, scattering from the surfactant. We are currently undertaking a more detailed analysis of the existing data to account for these factors, and these simulations will be reported at a later date, along with additional data from experiments that are currently in progress.…”

mentioning

confidence: 53%

New Phosphate Fluorosurfactants for Carbon Dioxide

Keiper¹,

Simhan²,

DeSimone³

et al. 2002

J. Am. Chem. Soc.

113

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The vast potential of carbon dioxide (CO 2 ) as an environmentally clean, abundant, and tunable solvent is now being realized on a variety of fronts, including cleaning protocols in microelectronics and garment care industries, coatings, and polymer production and processing. 1 To take advantage of CO 2 's benefits, however, it is often necessary to confront an important limitation, namely its low capacity for solubilizing many materials, including water. 2 One way this issue has been addressed is through the use of small-molecule fluorosurfactants to aid the dispersion of water-in-CO 2 (W/C). 3 Unfortunately, only a handful of surfactants have proven capable of water uptake in neat CO 2 . Here, we report initial findings on chemically homogeneous anionic phosphate fluorosurfactants that enable significant water uptake within a continuous CO 2 phase, through the formation of W/C microemulsions without the aid of a cosurfactant. 4 The double-tailed surfactants are of two general structural types: a form containing two fluorinated chains (1) and a "hybrid" form 3a containing one fully hydrocarbon chain and one fluorinated chain (2). Two such surfactants, which can be prepared in a straightforward manner in high purity, 5 are shown below.Ionic solutes generally possess low solubility in compressed CO 2 . 2 This was indeed the case for surfactant 1, which was insoluble at 1 wt % at temperatures from 25 to 65°C and pressures up to 380 bar. 6 Surfactant 2 proved soluble at 1 wt % under rather mild pressures (for example, cloud points at 60 and 27°C occurred at 225 and 119 bar, respectively). It is not clear why the hybrid surfactant 2 has such appreciable "dry" solubility in CO 2 , although self-assembly into reverse micelles, perhaps with internal cores incorporating the hydrocarbon chain, is one possibility. Addition of water to either surfactant in CO 2 allowed for the formation of clear, single-phase solutions. Cloud point profiles of 2.5 wt % surfactant solutions in CO 2 with varied water/surfactant molar ratios (W o ) 7 are shown in Figure 1, where homogeneous solutions existed at pressures above the curves and heterogeneous, phase-separated solutions existed below the curves. For surfactant 1, the cloudpoint behavior followed essentially linear trends for water loadings spanning from W o ) 11 up to at least 45 (for W o ) 45 there were equivalent weights of water and surfactant). The cloud-point pressure ranges observed here were comparable to those determined for W/C microemulsion-forming fluorosurfactants at similar temperatures and concentrations (Figure 1a). 3 The phase behavior for surfactant 2 was not straightforward. At W o ) 11, cloud-point pressures curved upward as temperatures decreased, while for W o ) 17 and 34, cloud-point pressures decreased rather linearly ( Figure 1b). Opposite trends were recently reported for a cationic perfluoropolyether surfactant in CO 2 . 8 Considering the high analytical purity of the surfactant and the reproducibility of the cloud-point measurements ((0.5 bar), we sp...

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mentioning

confidence: 53%

New Phosphate Fluorosurfactants for Carbon Dioxide

Keiper¹,

Simhan²,

DeSimone³

et al. 2002

J. Am. Chem. Soc.

113

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“…The graft copolymer with a PFOA backbone and poly(ethylene oxide) (PEO) grafts formed micelles which stabilized water in CO 2 , while the PTFE-b-PEO copolymer formed reverse micelles, and F(CF 2 ) 10 (CH 2 ) 10 H formed small aggregates of at most four chains. The block copolymer PS-b-PFOA forms micelles in CO 2 with a PS core and a PFOA shell and the data fits a polydisperse spherical core-shell model [45,46]. With an increase in CO 2 density, the change in polydispersity suggests the existence of a critical micelle density, or a density of CO 2 above which the micelles are broken up into soluble unimers.…”

Section: Characterizationmentioning

confidence: 73%

“…Depressurization of the CO 2 or changing the CO 2 density will cause the contaminant to be released from the surfactant. For example, a block copolymer was used to extract deuterated oligomers into CO 2 [45], and a dendrimer was used to extract a water soluble, CO 2 -insoluble dye from the water phase into the CO 2 phase [52]. Detergents for CO 2 can be used for cleaning applications, such as "dry cleaning" using liquid CO 2 as the solvent instead of the common perchloroethylene, a probable human carcinogen [53].…”

Section: Applications and Outlookmentioning

confidence: 99%

Frontiers in green chemistry utilizing carbon dioxide for polymer synthesis and applications

Young

DeSimone

2000

Pure and Applied Chemistry

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“…Eventually, with the discovery that fluoropolymers and polysiloxanes were indeed soluble in CO 2 , steric stabilizers were envisioned to stabilize emulsion and dispersion polymerizations in a CO 2 continuous phase. These surfactants consist mostly of amphiphilic block copolymers that have "CO 2 -philic" and "CO 2 -phobic" components, comprised of a polysiloxane or fluoropolymer block and a hydrophilic or lipophilic polymer block, respectively [13][14][15]. Self-assembly leads to the formation of micelles having a core of the CO 2 -phobic blocks adsorbed to the polymer and an outer corona of the CO 2 -philic blocks dispersed in CO 2 .…”

Section: Surfactantsmentioning

confidence: 99%

Developments in CO2 research

Behles

DeSimone

2001

Pure and Applied Chemistry

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CO 2 can be a good solvent for many compounds when used in its compressed liquid or supercritical fluid state. Above its critical temperature and critical pressure (T c = 31 °C, P c = 73.8 bar), CO 2 has liquid-like densities and gas-like viscosities, which allows for safe commercial and laboratory operating conditions. Many small molecules are readily soluble in CO 2 , whereas most macromolecules are not. This has prompted development of several classes of small molecule and polymeric surfactants that enable emulsion and dispersion polymerizations as well as other technological processes.

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Design of Nonionic Surfactants for Supercritical Carbon Dioxide

Cited by 270 publications

References 23 publications

New Phosphate Fluorosurfactants for Carbon Dioxide

New Phosphate Fluorosurfactants for Carbon Dioxide

Frontiers in green chemistry utilizing carbon dioxide for polymer synthesis and applications

Developments in CO2 research

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