Micellar Properties of a New Series of Stereochemical Sodium Carboxylates Bearing Double Bonds near Their Ionic Heads in Aqueous Media
✍ Scribed by Christine Damas; Ludovic Vannier; Mohamed Abarbri; Alain Duchene; Robert Coudert
- Book ID
- 102579579
- Publisher
- Elsevier Science
- Year
- 1998
- Tongue
- English
- Weight
- 194 KB
- Volume
- 198
- Category
- Article
- ISSN
- 0021-9797
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✦ Synopsis
the CMC of unsaturated compounds is higher than that of The critical micelle concentrations (CMCs) of sodium carboxyltheir homologous saturated derivatives as shown by the studates bearing one or two double bonds near the polar head are ies of Durairaj et al. (8), Sprague et al. (9), and Larabee determined at various temperatures using cryoscopy, conductimeet al. (10) on sodium carboxylates. Furthermore Yokoyama try, and vapor pressure osmometry techniques. CMC increases et al. (11) observed a similar effect with eicosapolyenoic with temperature in the range 25 to 40ЊC. The enthalpy for micelliacids bearing more than one double bond (2 to 5) located zation of monoenic and dienic compounds is determined above in the central part of the hydrophobic tail.
25ЊC and found to be negative. The exothermic micellization pro-The CMC increase indicates a decreased hydrophobicity cess is attributed to the rigidity of the polar head group which in the unsaturated chain in comparison with the homologous inhibits molecular interactions in the micellar state. CMC increases with increasing number of double bonds. The free energy saturated chain. Thus a double bond appears to be less hyof micellization per unsaturated CH group ( DG m (CH)) is then drophobic than a single bond. To the best of our knowledge, determined. The values obtained, which are 01.83, 01.56, 01.27, we are not aware of any study in the literature involving and 01.18 kJrmol 01 at 0, 25, 33, and 40ЊC, respectively, are higher systems with a stereochemical double bond located near the than those of CH 2 group, i.e., 02.53 { 0.15 kJrmol 01 in the same polar head of a surfactant series. Therefore this paper examtemperature range. The unsaturated CH group has thus a less ines some original thermodynamical properties of alkyl sohydrophobic character. Moreover the DG m (CH) value of the comdium carboxylates bearing double bonds in a (2E) or a, d pounds studied here is found to be lower than the DG m (CH) value (2E, 4E) position, in order to correlate their chemical strucof end-tail double-bond surfactants. Based on these results, it is ture and micellar properties. For this purpose the followconcluded that the closer the double bond to the polar head, the ing sodium carboxylates have been synthesized: CH 3 { higher the hydrophobic character. ᭧ 1998 Academic Press ({CH 2 {) x04 {CH|CH{COO 0 Na / , with x Å 10, 12,