| Zugriffsnummer | 24064 |
| Dokumenttyp | Zeitschriftenartikel |
| Sprache | Englisch |
| Titel | Ultrasonic spectrometry of aqueous solutions of alkyl maltosides: kinetics of micelle formation and head-group isomerization |
| Autor(in); Institution |
Haller, Julian; 1.6, Schall, PTB-Braunschweig; Georg-August-Universität Göttingen, Drittes Physikalisches Institut, Göttingen, GERMANY
Kaatze, Udo; Georg-August-Universität Göttingen, Drittes Physikalisches Institut, Göttingen, GERMANY
|
| Quelle/Jahr | ChemPhysChem: 10 (2009), 15, 2703 - 2710 |
| ISSN | 1439-4235 (PRINT) ; 1439-7641 (ONLINE) |
| DOI | |
| Verlag | Weinheim: Wiley-VCH |
| Klassifikationscode | PACS: 43.35.Bf ; PACS: 43.45.Fj ; PACS: 61.25.Em ; PACS: 62.80.+f ; PACS: 43.35.+d |
| Freie Schlagworte | glycosides ; kinetics ; micelles ; surfactants ; ultrasonic spectrometry |
| Zusammenfassung | At frequencies between 100 kHz and 400 MHz, ultrasonic attenuation spectra are measured at 25 °C for aqueous solutions of hexyl-, heptyl-, octyl-, nonyl-, and decyl-β-D-maltopyranoside as well as of decyl-α-D-maltopyranoside. The spectra with surfactant concentration c above the relevant critical micelle concentration (cmc) display three relaxation terms with discrete relaxation times. That with a relaxation time between 0.1 and 1.2 μs is due to exchange of monomers between micelles and the suspending phase. It is discussed in the light of the Teubner-Kahlweit-Aniansson-Wall model of the formation/decay kinetics of systems with Gaussian size distribution of micelles. The relaxation parameters are compared to those for solutions of other non-ionic surfactants, such as alkyl monoglycosides and poly(ethylene glycol) monoalkyl ethers. At c(cmc this low-frequency relaxation term is missing and at c≈cmc it is broadened, as is characteristic of solutions of oligomeric molecular structures rather than proper micelles. The relaxation terms with relaxation times between 6 and 15 ns and 0.7 and 2.3 ns reveal head-group rotations around glycosidic angles and isomerization of the exocyclic hydroxymethyl group, respectively. These unimolecular reactions are also examined with a view to solutions of alkyl monoglycosides as well as of glucose and maltose. |
