Critical micelle concentration hydrocarbon-fluorocarbon

For an a-helical fraction fH = 0,5 30% methanol, 20% ethanol, 15% i-propanol or 10% trifluoroethanol are necessary. Trifluoroethanol like perfluorinated alcohols, e.g. hexafluoroisopropanol is characterised on the hand by a strong acidic proton at the OG-group due to the —1-effect of the fluor atoms. On the other hand fluorocarbons are more hydrophobic than the hydrocarbons which is mainly due to the larger surface of the F compared with H. For this reason the critical micelle concentration of perfluorinated detergents is much lower than that of the corresponding hydrocarbon compounds. It was found that C4F7-derivatives act as detergents... 

We have recently synthesized new types of water-soluble copolymers containing fluorocarbon moieties [10-13]. This type of copolymer would appear to have advantages over the corresponding hydrocarbon analogs. First, fluorocarbons appear to possess greater apparent hydrophobic character [14,15]. This is reflected in critical micelle concentrations of perfluorocarbon... 

In analogy to surfactants with a hydrocarbon chain, the critical micelle concentrations for fluorinated surfactants in an aqueous solution depend on the fluorocarbon chain length and the counterion (Table 6.9) [58,59,75,77,96,139, 146-154] and decrease with increasing hydrophobe chain length. 

The critical micelle concentrations of fluorinated surfactants are compared with those of hydrocarbon surfactants in Table 6.11 [59,157]. The cmc values for C7 and Cg fluorinated surfactants are approximately equal to those for Ci 1 and C12 hydrocarbon surfactants, respectively. The greater hydrophobicity of the fluorocarbon chain enhances the amphiphilic character of the surfactant and increases surface activity, reflected in surface tensions below 20 dyn/cm and lower cmc values [1,159]. Perfluorination reduces cmc values about four times per —CF2— group. The A value [or K value in Eq. (35)] does not change considerably with the type of the surfactant. Because the relation expressed by Eq. (34) is exponential, the cmc value of a fluorinated surfactant is approximately equal to that of a hydrocarbon surfactant with a hydrocarbon chain 1.5-1.7 times longer than the fluorocarbon chain [59,157,160]. 

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