Surfactants fluorocarbon hybride

A fVo of 32 was attained using a two-tailed hydrocarbon-fluorocarbon hybrid surfactant C7Fi5CH(OS03 Na )C7Hi5 (designated F7H7) [53]. This high value of Wo was for a one-phase system at 25°C and 231 bar, far in excess of any other surfactant... 

Flarrison K, Goveas J, Johnston KP, O Rear EA. Water-in-carbon dioxide microemulsions with a fluorocarbon-hydrocarbon hybrid surfactant. Langmuir... 

Dupont, A., Eastoe, J., Martin, L., Steytler, D.C., Heenan, R.K., Guittard, F. and Taffin de Givenchy, E. (2004) Hybrid fluorocarbon-hydrocarbon C02-philic surfactants. 2. Formation and properties of water-in-C02 microemulsions. Langmuir, 20, 9960. 

Harrison et al. reported the first w/c microemulsion in 1994 (20). A hybrid surfactant, namely F7H7, made of respectively one hydrocarbon and one fluorocarbon chain attached onto the same sulfate head group, was able to stabilize a w/c microemulsion at 35 and 262 bar. For a surfactant concentration of 1.9 wt %, water up to a w = 32 value ([water]/surfactant]) could be dispersed. A spherical micellar structure was confirmed by small-angle neutron scattering (SANS) experiments (21). This surfactant was later the subject of dynamic molecular simulations (22, 23). The calculations were consistent with the SANS data and high diffusivity was predicted, highlighting this important feature of low-density and low-viscosity supercritical fluids (SCF). 

Huang Y, Read RW, Wang X (2010) Efficient alkylation methods for the synthesis of hybrid fluorocarbon-hydrocarbon tetrazoles as potential fluorinated surfactants. Aust J Chem... 

There is one major drawback to supercritical CO2 as a solvent. CO2 has an extremely low polarizability/volume ratio and hence is a somewhat feeble solvent. Many lipophilic and hydrophilic compounds are not soluble in CO2. In order to render CO2 a better solvent for these compounds, surfactants are necessary yet an extensive study by Consani and Smith showed that commercially available surfactants exhibit low solubility in CO2 (5). However, Consani did And that some fluorinated surfactants would appreciably dissolve in CO2. Indeed, hybrid fluorocarbon/hydrocarbon surfactants were shown to form water-in-C02 microemulsions (6,7). This chapter will focus on new developments in the de-... 

Hybrid anionic surfactants contain a fluorocarbon chain, a hydrocarbon chain, and a hydrophilic head group in the same molecule. Guo et al, [149] synthesized hybrid surfactants by the reaction scheme shown in Fig. 2.8. The hydrophilic group... 

In aqueous solutions, the surface tensions of these hybrid surfactants are about equal or slightly lower than that of the corresponding surfactant with a single hydrophobe. The cmc values are relatively low and are governed by the Kleven equation. The increase of the hydrocarbon-chain-length by a CH2 group decreases the cmc by about 35%. The increase of the fluorocarbon chain by each -CF2- group decreases the cmc by about 75%. Quantitative analysis of the F-NMR spectra has revealed that the residence time of the fluorocarbon chain in... 

The Krafft point, the area occupied by a surfactant molecule at the air-water and octane-water interfaces, and the aggregation number of micelles increase with an increase in fluorocarbon and/or hydrocarbon chain length of these hybrid surfactants [209]. The cmc, surface tension, and octane-water interfacial tension at the cmc decrease with an increase in fluorocarbon and/or hydrocarbon chain length. The surfactants lower the surface tension, as well as the hydrocarbon oil-water and the water-fluorocarbon oil interfacial tension. Their solutions in water can float on hydrocarbon liquids, such as benzene, cyclohexane, and decane. The 10% solution of the surfactant with m = 6 and n = 4 chains exhibit rubberlike viscoelasticity [210]. 

Ito et al. [73] examined the micellization of fluorocarbon-hydrocarbon hybrid surfactants by Raman spectroscopy. The spectrometer was equipped with a multireflection cell and an optical-fiber light-collecting device [74]. The Raman spectra were obtained at high surfactant concentrations above the cmc, because the Raman intensity below cmc was too weak to be measured. 

The first water-in-C02 microeniulsion was reported in 1994 by Harrison et al. [7], who used a dichain anionic surfactant consisting of one hydrocarbon and one fluorocarbon chain attached to the same sulfonate head group [C7Fi5CH(OSOJNa" )C7Hi5]. When mixed with water and CO2, this hybrid... 

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