| Attributs | Valeurs |
|---|
| type
| |
| Is Part Of
| |
| Subject
| |
| Title
| - Calorimetric Study on the Temperature Dependence of theFormation of Mixed Ionic/Nonionic Micelles
|
| has manifestation of work
| |
| related by
| |
| Author
| |
| Abstract
| - The differential excess enthalpy of mixed micelle formation was measured at different temperaturesby mixing nonionic hexa(ethylene glycol) mono n-dodecyl ether with anionic sodium dodecyl sulfate orcationic dodecylpyridinium chloride. The experimental data were obtained calorimetrically by titratinga concentrated surfactant solution into a micellar solution of nonionic surfactant. The composition andthe size of the mixed nonionic/ionic micelles at different surfactant concentrations were also determined.Pronounced differences in both composition and excess enthalpy were found between the anionic and thecationic mixed system. For both systems, the excess enthalpies become more exothermic with increasingtemperature, but for the anionic mixed system an additional exothermic contribution was found whichwas much less temperature dependent. Temperature dependence of the excess enthalpy was attributedto the effect of the ionic headgroup on the hydration of the ethylene oxide (EO) groups in the mixed corona.Ionic headgroups located in the ethylene oxide layer cause the dehydration of the EO chains resulting inan additional hydrophobic contribution to the enthalpy of mixing. A high affinity of sodium dodecyl sulfatefor nonionic micelles and an extra exothermic and less temperature dependent contribution to the excessenthalpy found for the SDS−C12E6 system might be attributed to specific interactions (hydrogen bonds)between the sulfate headgroup and the partly dehydrated EO chain.
|
| article type
| |
| is part of this journal
| |
