Leïla Ghannam

A versatile route to functional biomimetic coatings: ionomers for honeycomb-like structures

Highly ordered films were prepared by spreading out carbon disulfide (CS) solutions of ionomers over inorganic surfaces and for the first time over an organic surface. These ionomers, hydrophobic homopolymers or copolymers end-capped by a cationic group, were easily synthesized in a one-step reaction by a control radical process called nitroxide-mediated polymerization. Optical and electronic microscopy observations of the films lead to the definition of new criteria for the formation of such structures. Firstly, the effect of a solid support on the honeycomb structure regularity was studied. By comparing two polar substrates, it was found that a more regular organization is obtained over mica than over glass. This phenomenon may be due to the electrostatic interactions between cationic ionomer ends and oxanions of the mica surface. Moreover, for the first time, highly ordered hexagonal patterns were also created on a flexible and soft polymeric surface, a poly(vinyl chloride) sheet. Secondly, it was found that the characteristics of the polymeric chain of the ionomer and mainly its glass transition temperature play an important role in the process of formation of ordered structures. The iridescent aspect of the films, due to light diffraction and optical interferences, was studied and quantified by spectrogoniometry. Finally, results of measurements of superficial tension are discussed; the presence of a honeycomb film at the surface of a material very significantly enhances its hydrophobicity. All these criteria of highly ordered structures correlated to a water repellency and iridescent behaviours lead to a functional biomimetic material.

Functionalization of SBA-15 materials for the adsorption of phenols from aqueous solution

Water pollution by toxic organic compounds is a problem and demand for efficient adsorbents for the removal of toxic compounds is increasing. In the present work, we studied the functionalization of SBA-15 materials via the co-condensation between an alkoxysilane and an organoalkoxysilane in the presence of P123 as structuring agent. Several types of ligands were used: 3-mercaptopropylmethyldimethoxysilane, N-[3-(trimethoxysilyl) propyl] aniline; aminopropyltrimethoxysilane; [aminoethylamino]-propyltrimethoxysilanes and [(2-aminoethylamino) ethylamino] propyltrimethoxysilanes. These materials exhibit BET surface area of 275–776 m2/g and total pore volume of 0.29–1 cm3/g, depending on the ligand types and contents. Elementary analysis results confirm the incorporation of both thiol and amine group in the materials. Batch adsorption studies shows that the adsorption capacity of phenol drifts on the amine and thiol functionalized SBA-15 is greater than that on pure SBA-15. A linear relationship was observed between the adsorption capacity and N/SiO2 ratio. It was shown that the presence of amine promotes interactions with water molecules, on the other hand, these results can also be explained by the basic behavior of N-functionalized materials.

Diglycolamide-functionalized resorcinarene for rare earths extraction

A C-methylcalix(4)methylresorcinarene–DODGA ligand, derived from calix[4]methylresorcinarene functionalized with four diglycolamide (DGA) binding units, was synthesized and characterized by NMR and MS. The ligand was investigated with respect to the extraction of rare earth elements (REEs) from nitric acid solution. High sensitivity was observed, particularly toward heavy rare earth elements. The acidity effects, as well as the concentration of the extractant, were evaluated with regard to the extraction and separation efficiencies. The results showed that the distribution coefficient values increase with an increase in nitric acid concentration in the range from 0.1 to 5 mol L−1. A slope analysis method and spectrophotometric titrations showed clear complexation of the REEs with the ligand. An extraction mechanism is proposed from the estimation of the thermodynamic parameters (ΔH, ΔS, and ΔG). The extraction and stripping of REEs from a simulated leaching solution of a Nd/Fe/B/Dy magnet have been studied.

Structure and permanent electric dipole of para-fluoroaniline in gaseous phase

By coupling a matrix assisted laser desorption source to an electric beam deflection setup, we have measured the permanent electric dipole moment of the isolated para-fluroaniline PFAN (FC6H4NH2) molecule in the ground state. This measurement of the electric dipole of an isolated push-pull molecule is unique. The experimental value is compared to two different calculations and the structure of the system is discussed.Graphical abstract