Supramolecular Assemblies Obtained by Mixing Different Cyclodextrins and AOT or BHDC Reverse Micelles

OSCAR FERNANDO SILVA; N. MARIANO CORREA; JUANA J. SILBER; RITA H. DE ROSSI; MARIANA A. FERNÁNDEZ

LANGMUIR

AMER CHEMICAL SOC

Lugar: Washington; Año: 2014 vol. 30 p. 3354 - 3362

0743-7463

In this contribution we show the effect of the surfactant polar head and the external solvent on the incorporation of different cyclodextrins (CDs): α-CD, β-CD, -CD, decenylsuccinyl-b-CD (Mod-b-CD) and hydroxypropyl-b-CD (hp-b-CD) in different RMs: benzene/sodium 1,4-bis (2-ethylhexyl) sulfosuccinate(AOT)/water, benzene/ benzyl-n-hexadecyldimethylammonium chloride (BHDC)/water and compare them with previous results obtained in n-heptane/AOT/water RMs. In order to investigate the different systems we have used UV?Vis and induced circular dichroism spectroscopy (ICD) and the achiral molecular probe methyl orange (MO). The results show dramatic differences changing the external solvent and the surfactant which are explained considering the differences in the RMs interfaces composition, the water-surfactant interaction and the CDs location in the different media investigated. None of the CDs were incorporated in the benzene/AOT/water RMs at any W0 value studied while it was previously shown that Mod-b-CD and hp-b-CD could be included in n-heptane/AOT/water RMs. On the other hand, all the CDs are incorporated in benzene/BHDC/water RMs at W0> 10 and hp-b-CD is dissolved even at W0 = 0. Different to what it was found in n-heptane/AOT RMs, in BHDC RMs MO showed ICD signals with two different CDs: Mod-b-CD and hp-b-CD. The results are explained considering the known difference in the interfacial water structure for AOT and BHDC RMs and, the electron rich region on the secondary hydroxyl (wider side of the CDs) which helps to solubilize all CD in BHDC. This study shows that the chiral cyclodextrin could be available for a guest in an organic medium such as the RMs. Therefore we have created a potentially powerful nanoreactor with two different confined regions in the same aggregate: the polar core of the RMs and the chiral hydrophobic cavity of cyclodextrin.