title: Chiroptical phenomena in reverse micelles: the case of (1R,2S)-dodecyl (2-hydroxy-1-methyl-2-phenylethyl)dimethylammonium bromide (DMEB).
abstract: (1R,2S)-Dodecyl(2-hydroxy-1-methyl-2-phenylethyl)dimethylammonium bromide (DMEB) aggregates dispersed in carbon tetrachloride have been investigated by Fourier transform infrared (FT-IR), vibrational circular dichroism (VCD) and (1)H nuclear magnetic resonance (NMR) spectroscopy at various surfactant concentration and water-to-surfactant molar ratio. Experimental data indicate that, even at the lowest investigated concentration and in absence of added water, DMEB molecules associate in supramolecular assemblies. At higher DMEB concentration the aggregates can confine water molecules, making it plausible to think that DMEB form reverse micelles and that water molecules are quite uniformly distributed among them and mainly located in the proximity of surfactant head groups. Moreover, the water state in DMEB reverse micelles has been found to be different from that in pure water, due to system-specific water/surfactant head group interactions. (1)H NMR diffusion measurements of both water and DMEB emphasize their joined translational motion characterized by a diffusion rate one order of magnitude lower than that of free molecules. Finally, VCD allowed us to show some characteristics of the association of optically active DMEB molecules as reverse micelles and water confinement inside; namely, we monitored the vibrational optical activity of deuterated hydroxyl bonds of the self-assembled DMEB molecules and their interaction with D(2)O molecules.
authors.affiliation: Dipartimento di Medicina Molecolare e Traslazionale, Università di Brescia, Brescia, Italy; Consorzio Interuniversitario Scienze Fisiche della Materia, Roma, Italy.
authors.forename: Sergio
authors.initials: S
authors.lastname: Abbate
authors.forename: Marco
authors.initials: M
authors.lastname: Passarello
authors.forename: France
authors.initials: F
authors.lastname: Lebon
authors.forename: Giovanna
authors.initials: G
authors.lastname: Longhi
authors.forename: Angela
authors.initials: A
authors.lastname: Ruggirello
authors.forename: Vincenzo
authors.initials: V
authors.lastname: Turco Liveri
authors.forename: Fiorenza
authors.initials: F
authors.lastname: Viani
authors.forename: Franca
authors.initials: F
authors.lastname: Castiglione
authors.forename: Daniele
authors.initials: D
authors.lastname: Mendola
authors.forename: Andrea
authors.initials: A
authors.lastname: Mele
keywords: (1R,2S)-dodecyl(2-hydroxy-1-methyl-2-phenylethyl)dimethylammonium bromide (DMEB); PGSE-NMR; confinement effects; hydrogen bonding; reverse micelles; vibrational circular dichroism (VCD)