Salima Saidi-Besbes

Structure–property study of new [1,2,3]-triazole liquid crystalline derivatives

The synthesis of a new type of liquid crystalline compound derived from 1,2,3-triazole was achieved using Wittig reaction. Polarised microscopy studies, X-ray scattering and differential scanning calorimetry analysis revealed that the target compounds exhibit enantiotropic liquid crystalline properties. Their mesomorphic behaviour is closely related to the nature of substituents in position N1 of the heterocycle, the length of the mesogenic core as well as the isomerisation nature (E/Z) of the double bond.

Copolymerization of novel reactive fluorinated acrylic monomers with styrene: reactivity ratio determination

The radical copolymerization of three polymerizable surfactants with styrene was investigated by NMR spectroscopy to assess their compositions. The reactivity ratios of these monomers were calculated according to the methods of Fineman–Ross and Kelen–Tüdos. Consequently, Q and e values were deduced by the Alfrey and Price method. The results indicated the positive effect of the fluorine chain on the reactivity of monomers bearing a long spacer between the ammonium head and the acrylic function. These monomers exhibit high e values which are in favor of an intramolecular conformation of the surfactant where the ester carbonyl function of the polymerizable group interacts with the onium nitrogen atom via a compact six-sided structure.

Investigation of structure–surface properties relationship of semi-fluorinated polymerizable cationic surfactants

Novel hybrid hydrocarbon/fluorocarbon ammonium type surfactant monomers (surfmers) of the general formula RF (CH2)l N(CH3)2(CH2)mOCOCH=CH2 with (RF=C4F9, C6F13, C8F17, l=4, 6, 11, and m=2-11) were synthesized and characterized. They exhibit very low surface tension as well as low critical micellar concentrations down to 1.39×10(-5)mol/L. Special attention was focused on theeffect of the polymerizable moiety, the length of the hydrocarbon spacers, and the fluorinated chains on surface activities of the reactive surfactants as compared to hydrocarbon surfmer analogs. Results indicate that the acrylic function has a pronounced effect on increasing the hydrophobic micelle character. This was confirmed by surface tensions and average surfaces occupied by these molecules at the water-gas interface. The micellar sizes were investigated by dynamic light scattering.

Synthesis and mesomorphic behaviour of unsymmetrical tetracatenar [1,2,3]-triazole derivatives

ABSTRACT New nonsymmetric four-chained and three-chained [1,2,3]-triazole derivatives were synthesised. Their phase behaviours were investigated by differential scanning calorimetry, polarised optical microscopy and X-ray diffraction analyses. The tetracatenar derivatives show a columnar mesophase and a lamellar crystalline phase. The effects of the length of the terminal alkoxy chain and the nature of the terminal group attached to the side phenyltriazole unit of the mesogenic core are discussed. GRAPHICAL ABSTRACT

[1,2,3]-triazole derivatives: Mesomorphic property dependence on the molecular shape

ABSTRACT Nowadays, heterocyclic units have been extensively studied for the preparation of thermotropic liquid crystals due to their ability to impart lateral and/or longitudinal dipoles and induce changes in molecular shape. Key parameters to accede to stable mesophases are the position of the heterocycle and the nature of terminal and linking functions. We present in this paper, an overview of several series of 1,2,3-triazole liquid crystalline derivatives that we designed and characterized. We highlight the effect of different connecting functions and the geometry of mesogenic core on the mesomorphic behavior of these derivatives.

Preparation and Characterization of Poly(methyl methacrylate) Particles by Combined Dispersion and Emulsion Polymerization

Monodispersed poly(methyl methacrylate) (PMMA) nanoparticles were synthesized by combined dispersion and emulsion polymerization, using aqueous alcohol (methanol/water) as the dispersion medium. The influence of the dispersion medium ratio, stabilizer concentration, and initiator type and concentration on the colloidal stability, particle size, size distribution, and %conversion, was investigated. Submicron PMMA particles with a size of approximately 760 nm with a narrow size distribution, high conversion (91%) and good stability throughout the polymerization were obtained using a 50/50 methanol/water ratio, 1 wt% 2,2’-azobisisobutyronitrile (based on monomer), and 1 wt% polyvinylpyrrolidone (based on medium). With increasing the polarity of the dispersion medium (30/70 methanol/water ratio), the size and conversion of PMMA particles decreased to 345 nm and 72%, respectively.