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Deschenaux, Robert

Nom
Deschenaux, Robert
Affiliation principale
Fonction
Professeur ordinaire
Email
Robert.Deschenaux@unine.ch
Identifiants
https://libra.unine.ch/handle/123456789/384

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  • Publication
    Métadonnées seulement
    Liquid crystal nano-particles, LCNANOP - a SONS II collaborative research project
    (2008)
    Goodby, John W.
    ;
    Bates, Martin
    ;
    Saez, Isabel M.
    ;
    Gorecka, Ewa
    ;
    Kitzerow, Heinz- S.
    ;
    Guillon, Daniel
    ;
    Donnio, B.
    ;
    Serrano, Jose-Luis
    ;
    Deschenaux, Robert 
    A review. LC-NANOP is an ESF EUROCORES SONS Collaborative Research Project that is addressing an innovative approach to self-organized nanostructures by combination of a variety of org., inorg. and metal scaffolds with the unique self-organization properties of liq. crystals to obtain liq. crystal nano-particles. LC-NANOP is concerned with the synthesis, anal., characterization, modeling and physico-chem. properties of super- and supra-mol. systems which are formed from a nano-particle as a central scaffold, surrounded by a layer of liq. crystal. The self-organization properties of the liq. crystal coating is the driving force leading to the self-assembly of the nano-particles into secondary or tertiary hierarchical structures, with emphasis on the systematic variation of nano-particle size, chirality, shape and functionality. This bottom-up approach to nano-structuring is very powerful as it combines the extraordinary variety of morphologies that liq. crystals present with the combination of functional entities, relevant for chem., biol., optoelectronic, and photonic tasks, etc, to create ordered nano-structures that can be controlled by external stimuli. [on SciFinder(R)]
  • Publication
    Métadonnées seulement
    Liquid-Crystalline Janus-Type Fullerodendrimers Displaying Tunable Smectic-Columnar Mesomorphism
    (2007)
    Lenoble, Julie
    ;
    Campidelli, Stephane
    ;
    Maringa, Natacha
    ;
    Donnio, Bertrand
    ;
    Guillon, Daniel
    ;
    Yevlampieva, Natalia
    ;
    Deschenaux, Robert 
    Janus-type liq.-cryst. fullerodendrimers were synthesized via the 1,3-dipolar cycloaddtition of 2 mesomorphic dendrons and C60. By assembling poly(aryl ester) dendrons functionalized with cyanobiphenyl groups, displaying lamellar mesomorphism, with poly(benzyl ether) dendrons carrying alkyl chains, which display columnar mesomorphism, the authors could tailor by design the liq.-cryst. properties of the title compds. as a function of each dendron size. The liq.-cryst. properties were examd. by polarized optical microscopy, DSC, and x-ray diffraction. Depending on the dendrimer generations, smectic (SmC and/or SmA phases) or columnar (Colr-c2mm or Colr-p2gg phases) mesomorphism was obtained. The supramol. organization is governed by (1) the adequacy of the cross-sectional area of the dendrons, (2) the microsegregation of the dendrimer, (3) the deformation of the dendritic core, and (4) the dipolar interactions between the cyanobiphenyl groups. Comparison of the mesomorphic properties of 2 fullerodendrimers with those of model compds. (fullerene-free analogs) indicated that the C60 unit does not influence the type of mesophase that is formed. Mol. properties detd. in soln. (permanent dipole moment, specific dielec. polarization, molar Kerr const.) confirm that microsegregation persists in soln. and strengthen the models proposed for the structure of the mesophases. [on SciFinder(R)]
  • Publication
    Métadonnées seulement
    Ferrocene-containing optically active liquid-crystalline side-chain polysiloxanes with planar chirality
    (2006)
    Brettar, Julie
    ;
    Burgi, Thomas
    ;
    Donnio, Bertrand
    ;
    Guillon, Daniel
    ;
    Scharf, Toralf
    ;
    Deschenaux, Robert 
    Optically active liq.-cryst. side-chain polysiloxanes have been prepd. by grafting planar chiral ferrocene-based vinyl monomers onto com. available polyhydrosiloxane. Two ferrocene monomers have been synthesized: a linear-type monomer, which displays a monotropic chiral smectic C (SC*) phase and enantiotropic smectic A (SA) and chiral N (N*) phases, and a laterally branched monomer, which shows an enantiotropic N* phase. X-ray diffraction anal. indicates a monomol. organization of the monomeric units within the smectic layers. The polymers retain the liq.-cryst. phases of their corresponding monomers. The UV-vis and CD (CD) spectra are in agreement with the structure of the monomers and polymers. The molar absorption coeff. (?) and molar circular dichroic absorption coeff. (??) values of the polymers are proportional to the no. of monomeric units grafted onto them. The abs. configuration of the ferrocene carboxylic acid intermediate, used to synthesize the monomers, has been detd. on the basis of CD spectra. The helical twisting power (HTP) of the nematogenic monomer and polymer have been detd. in E7, and indicate that such materials could be used as chiral dopants. Finally, this study demonstrates that the nature of chiral phases can be controlled by structural engineering of the org. groups only, with ferrocene acting as the source of chirality. [on SciFinder(R)]
  • Publication
    Métadonnées seulement
    Liquid-Crystalline Fullerodendrimers which Display Columnar Phases
    (2006)
    Lenoble, Julie
    ;
    Maringa, Natacha
    ;
    Campidelli, Stephane
    ;
    Donnio, Bertrand
    ;
    Guillon, Daniel
    ;
    Deschenaux, Robert 
    The title compds. were synthesized by applying the 1,3-dipolar cycloaddn. reaction of aldehyde-based poly(benzyl ether) dendrimers and sarcosine (N-methylglycine) to [60]fullerene (C60). The dendritic building blocks used to functionalize C60 displayed cubic and hexagonal columnar phases. The fullerene derivs. showed rectangular columnar phases of c 2. mm symmetry. [on SciFinder(R)]
  • Publication
    Métadonnées seulement
    Amphiphilic and mesomorphic fullerene-based dendrimers
    (2003)
    Guillon, Daniel
    ;
    Nierengarten, Jean-Francois
    ;
    Gallani, Jean-Louis
    ;
    Eckert, Jean-Francois
    ;
    Rio, Yannick
    ;
    del Pilar Carreon, Maria
    ;
    Dardel, Blaise
    ;
    Deschenaux, Robert 
    Growing attention is currently devoted to large dendritic structures for applications in nanotechnol. and materials science. In this respect, the incorporation of such compds. into thin ordered films appears to be an important issue. One of the most widely pursued approaches to structurally ordered dendrimer assemblies was the prepn. of Langmuir films at the air-water interface. We report on the case of a diblock globular fullerene-based dendrimer and show that peripheral substitution of the dendrimer with hydrophobic chains on one hemisphere and hydrophilic groups on the other provides the required hydrophobic/hydrophilic balance allowing the formation of stable Langmuir films. A second approach was to consider the case of fullerene contg. dendrimers terminated by mesogenic groups such as cyanobiphenyl subunits. Whatever the generation is, up to the fourth one, all these compds. exhibit a well-defined liq. cryst. smectic A phase. The mol. organization within the smectic layers is monolayered or bilayered depending on the generation. For the smallest dendrimers, the organization is mainly governed by the size of the fullerene moiety, whereas for the higher ones, it is governed by the interactions between the terminal mesogenic groups. These two approaches appear particularly interesting for functional groups such as fullerenes, which are not well adapted to be organized in nanoscale architectures. The present study shows that fullerenes can indeed be introduced into different types of ordered structure when they were chem. adequately modified. 3',3''-(Methanoxymethano[1,3]benzenomethanoxymethano)-3'H,3''H-dicyclop ropa[1,9:3,15][5,6]fullerene-C60-Ih-3',3''-dicarboxylic acid. [on SciFinder(R)]
  • Publication
    Métadonnées seulement
    Liquid-crystalline dendrimers
    (2003)
    Guillon, Daniel
    ;
    Deschenaux, Robert 
    A review. The supramol. organization of select liq.-cryst. dendrimers within lamellar, columnar, and nematic phases is discussed. Tuning of the mesomorphic structure can be achieved by an appropriate mol. design depending upon the chem. nature of the terminal mesogenic groups, dendritic core and dendrimer generation. High mol. wt. monodisperse dendrimers are promising candidates for the development of new liq.-cryst. materials contg. active mol. units for specific phys. properties. [on SciFinder(R)]
  • Publication
    Métadonnées seulement
    Aromatic Bent-Core Liquid Crystals: an Opportunity for Introducing Terdentate Binding Units into Mesophases
    (2002)
    Nozary, Homayoun
    ;
    Piguet, Claude
    ;
    Rivera, Jean-Pierre
    ;
    Tissot, Paul
    ;
    Morgantini, Pierre-Yves
    ;
    Weber, Jacques
    ;
    Bernardinelli, Gerald
    ;
    Buenzli, Jean-Claude G.
    ;
    Deschenaux, Robert 
    ;
    Donnio, Bertrand
    ;
    Guillon, Daniel
    Lipophilic linear semirigid side arms contg. two or three successive Ph rings sepd. by carboxylate spacers were connected to the 5 or 6 positions of bent arom. terdentate 2,6-bis(benzimidazol-2-yl)pyridine binding units to give extended V-shaped (L11) and I-shaped receptors (L12, L12b, and L13). The carboxylate spacers limit the flexibility of the side arms and provide crossed arrangements of the successive arom. rings in the crystal structure of L12b (C63H61N5O10; triclinic, space group P?1, Z = 2) in agreement with semiempirical calcns. performed on optimized gas-phase geometries. also, the carboxylate spacers in L11-L13 prevent efficient electronic delocalization between the connected arom. rings and act as weak ? acceptors producing a slight increase of the energy of the 1??* and 3??* levels centered on the terdentate binding unit. Intermol. ?-stacking interactions obsd. in the crystal of L12b are invoked to rationalize (i) the peculiar excimer emission of L11 in the solid state and (ii) the rich and varied calamitic (I-shaped L12, L12b, and L13) and columnar (V-shaped L11) mesomorphism obsd. at high temp. The ColR mesophase detected for L11 demonstrates that V-shaped bent terdentate binding units are compatible with liq.-cryst. behavior. Complexation of L11 with lanthanide(III) produces I-shaped complexes [Ln(L11)(NO3)3] (Ln = La, Eu, Gd, Tb, and Lu) possessing a large axial anisometry as found in the crystal structure of [Lu(L11)(CF3CO2)3(H2O)] (LuC81H87N5O17F9; triclinic, space group P?1, Z = 2), which exists in the solid state as H-bonded dimers. No mesomorphism is detected for the complexes as a result of the large perpendicular expansion brought by the metallic coordination site, but the high energy of the ligand-centered 3??* prevents Eu(5D0) ? L11 back transfer in the Eu(III) complex, which thus exhibits sizable red luminescence at room temp., a crucial point for the design of luminescent materials. [on SciFinder(R)]
  • Publication
    Métadonnées seulement
    Liquid-crystalline fullerene-oligophenylenevinylene conjugates
    (2002)
    Campidelli, Stephane
    ;
    Deschenaux, Robert 
    ;
    Eckert, Jean-Francois
    ;
    Guillon, Daniel
    ;
    Nierengarten, Jean-Francois
    Functionalization of C60-oligophenylenevinylene derivs. with a cyanobiphenyl-terminated dendromesogen leads to new donor-acceptor systems with liq.-cryst. properties. [on SciFinder(R)]
  • Publication
    Métadonnées seulement
    A mixed fullerene-ferrocene thermotropic liquid crystal: synthesis, liquid-crystalline properties, supramolecular organization and photoinduced electron transfer
    (2001)
    Even, Michael
    ;
    Heinrich, Benoit
    ;
    Guillon, Daniel
    ;
    Guldi, Dirk M.
    ;
    Prato, Maurizio
    ;
    Deschenaux, Robert 
    Grafting of a ferrocene-contg. liq.-cryst. malonate deriv. to C60 led to the mixed fullerene - ferrocene material 1 which gave rise to a smectic A phase. Cholesterol was used as liq.-cryst. promoter. X-ray diffraction expts. and volumetric measurements indicated that 1 is organized in double layered structures. The corresponding supramol. organization within the mesomorphic lamellar phase was characterized by a microsegregation of the different units (ferrocene, fullerene, and cholesterol) in distinct sublayers. In such a smectic A phase, C60 imposes the arrangement of the other mol. moieties. Photophys. studies revealed that electron transfer occurs from the donor ferrocene to the electron accepting fullerene. The formation of a long-lived radical pair, with lifetimes of the order of several hundred nanoseconds, was confirmed by time-resolved spectrometry, esp. in the near IR region, in which the radical anion of the fullerene moiety displays its characteristic fingerprint absorption. [on SciFinder(R)]
  • Publication
    Métadonnées seulement
    Switchable liquid-crystalline polymers based on the ferrocene-ferrocenium redox system
    (2001)
    Turpin, Francois
    ;
    Guillon, Daniel
    ;
    Deschenaux, Robert 
    A ferrocene-contg. side-chain liq.-cryst. polymethacrylate was oxidized with iodine into the corresponding ferrocenium polymeric species. The reduced polymer showed enantiotropic smectic C and smectic A phases. The oxidized polymer exhibited an enantiotropic nematic phase. The results described in this report confirm that ferrocene is a valuable redox-active unit for the design of switchable liq.-cryst. polymers. [on SciFinder(R)]