Dynamic surface packing in monolayers of mono-acylated b-cyclodextrin at the air-aqueous interface evidenced trough a PM-IRRAS study.
Raquel V. Vicoa, Rita H. de Rossib and Bruno Maggioa
Centro de Investigaciones en Química Biológica de Córdoba (CIQUIBIC-UNC-CONICET), Departamento de Química Biológica.a Instituto de Investigaciones en Fisicoquímica de Córdoba (INFIQC-UNC-CONICET), Departamento de Química Orgánica.b Facultad de Ciencias Químicas, Universidad Nacional de Córdoba. Haya de la Torre y Medina Allende, Ciudad Universitaria, X5000HUA, Córdoba. Argentina.
Cyclodextrins (CDs) are a group of well-known cyclic oligosaccharides with a hydrophobic internal nanocavity that enables complexation with different ligands. The presence of a single hydrocarbon chain linked to the cyclodextrin originates derivatives providing conformational flexibility to the nanocavity in monolayers at the air water/interface.1
Objectives
Determine the structural organization of a monoacylated-b-cyclodextrin (C16-bCD) film at the air/water interface through the analysis of IR bands obtained from PM-IRRAS spectra of monolayers under lateral compression.
Methods
Langmuir films of C16-bCD at defined surface pressures were analyzed through PM-IRRAS spectroscopy.
Results
The structural orientation of C16-bCD films as a function of surface pressure was accessed by the analysis of the variation of IR band relationship corresponding to specific vibrations of the cyclodextrin. Through PM-IRRAS analysis, it was possible to know the orientation adopted by de CD-rim relative to the interface, and to evidence the establishment of an intermolecular hydrogen-bond network that is important for the structural organization under close packing. As the surface pressure is increased, the nanocavity orientation becomes less accessible to ligands in the subphase while the hydrogen-bond network appears to determinate the surface properties of the film.
Conclusions
The surface properties displayed by the monoacylated-b-cyclodextrin films are of considerable interest in nanoscience and nanotechnology aimed at development of functional materials for diverse applications. The distinctive features showed by the film, such as the capability of storing chemical intermolecular information under defined structural control, could be used to regulate non covalent interactions between the CD nanocontainers at the interface with specific guests in the subphase, depending on the surface pressure at which the film is constrained.
1Langmuir 24:7867-7874, 2008.
