Noureddine Amdouni

Grafting β-Cyclodextrins to Silicone, Formulation of Emulsions and Encapsulation of Antifungal Drug

Emulsions of silicone polymers having β-cyclodextrin units as lateral chains have been prepared and used for the encapsulation of the antifungal drug griseofulvin. Such technology enables the formulation of active substances that are not soluble in water as dosage forms for topical administration.

Interfacial properties and thermodynamic behavior of cationic amphiphilic β-cyclodextrins substituted with one or seven alkyl chains

New cationic amphiphilic β-cyclodextrins (β-CD) were investigated for their surface-active properties and self-association. β-Cyclodextrin was mono- or per-substituted at its narrow rim by short (butyl) or long (dodecyl) aliphatic chains. The mono-substituted β-CDs are classical surfactants having a single hydrophobic tail and a single hydrophilic head; the per-substituted β-CDs have seven hydrophobic tails and seven hydrophilic heads. A comparative study of their surface-active properties at air/water and oil/water interfaces and of the formation of aggregates was achieved. All cationic β-CD surfactants show surface activity and self-assemble above a well-defined concentration referred to as the cmc because of the interactions between their hydrophobic tails. The inclusion of the alkyl chain inside the hydrophobic cavity did not cause other types of self-association. Though the main features of the surface-activity look similar to classical surfactants, such amphiphilic β-CDs show several specificities. The short-chained butyl derivatives behave as classical long-chained surfactants do. The head–tail interaction between the long dodecyl chain and the β-CD cavity of mono-substituted β-CD causes the formation of an intramolecular inclusion complex that weakens its hydrophobic character. The seven dodecyl chains of per-substituted β-CD tightly pack together, lowering the contact area with water and weakening their hydrophobic character. Part of the counterions of multi-charged per-substituted β-CD is associated as ion pairs with the cationic groups of the amphiphilic β-CD. A close analogy with the behavior of gemini surfactants is worth noticing.

Insulated molecular wires of polyaniline pseudopolyrotaxane

High density threading of cyclodextrins to conducting poly(aniline) as its emeraldine salt was achieved. Such insulated molecular wires were obtained using a strongly complexing chemically modified β-cyclodextrin. Inclusion complexation of the aniline monomer, polymerization of the inclusion complex, physicochemical characterizations of the polyaniline pseudopolyrotaxane and the electrical properties of its thin films are reported.

Structural and electrochemical properties of LiCoO2 and LiAlyCo1−yO2 (y=0.1 and 0.2) oxides: A comparative study of electrodes prepared by the citrate precursor route

We present the characterization and electrode behavior of LiCoO2 and Al-doped LiAlyCo1−yO2 (y=0.1 and 0.2) oxides prepared by wet-chemical method from the citrate precursor route. We study the phase evolution as a function of the aluminum substitution and the modification on the intercalation and deintercalation of Li ions. Characterization methods include XRD, SEM, and FTIR. X-ray diffraction patterns show that samples belong to the LiCoO2-LiAlO2 solid solution and have the layered α-NaFeO2 structure. FT-infrared vibrational spectroscopy indicates the slight modification in the local structure related to the short-range environment of oxygen coordination around the cations in oxide lattices. The frequencies and relative intensities of the bands are sensitive to the covalency of the (Al, Co)O2 slabs. The overall electrochemical capacity of the LiAlyCo1−yO2 oxides have been reduced due to the sp metal substitution, however, a more stable charge-discharge cycling performances have been observed when electrodes are charged to 4.3 V as compared to the performances of the native oxide. Differences and similarities between LiCoO2 and Al-substituted oxides are discussed therefrom.

Influence of the substitution of β-cyclodextrins by pyridinium groups on the complexation of adamantane derivatives

A series of positively charged β-cyclodextrin derivatives have been synthesized by selective functionalization of β-cyclodextrin at the primary rim with pyridinium groups. Characterisation of the modified β-cyclodextrin was done by elementary analysis, FTIR, 1H and 13C NMR spectroscopy. The inclusion complexation of adamantane derivatives (Adamantan-1-ol: AdOH and Sodium adamantane-1-carboxylate: AdCOO−Na+) by the host β-cyclodextrin and its grafted pyridinium derivatives has been investigated using 1H NMR spectroscopy. The stoichiometry of the complexes was found to be in 1:1 (adamantane:β-cyclodextrin) ratio. 1H chemical shift changes of adamantane protons were used to calculate the apparent binding constants of the complexes. Two dimentional NOESY experiments were performed to allow the mode of binding. Mono- and per-charged β-cyclodextrin showed an enhancement of inclusion binding ability towards the sodium adamantane-1-carboxylate guest. The origin of the observed enhancement in the stability of the complexes was ascribed to electrostatic interaction between carboxylate ion and charged pyridinium groups. A simple thermodynamic model of the electrostatic contribution to the complexation is presented.

Structural and Electrochemical Studies of Li-Co-Cr-O Oxides Prepared by Wet Chemistry

Substituted lithium cobaltates LiCo1-yCryO2 have been synthesized using four different low-temperature methods. These involved the mixing of either acetates or nitrates of the metals, Co and Cr, with a chelating agent in aqueous solution, namely citric acid for solgel method, oxalic acid for co-precipitation method, succinic acid for pyrolysis method or complexing agent glycine for combustion method. The synthesized products were characterized by DTA-TG, XRD, and FTIR. The electrochemical behavior of LiCo0.7Cr0.3O2 oxide was evaluated in lithium cell.