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Clemente M.J.,University of Zaragoza | Romero P.,University of Zaragoza | Serrano J.L.,University of Zaragoza | Fitremann J.,CNRS Laboratory for Molecular and Photochemical Reactions | Oriol L.,University of Zaragoza
Chemistry of Materials | Year: 2012

Supramolecular hydrogelators based on amphiphilic glycolipids have been prepared by clicking different sugar polar heads to a hydrophobic linear chain by copper(I)-catalyzed azide-alkyne [3 + 2] cycloaddition. The influence of the sugar polar head on the gelation properties in water has been studied, and the liquid crystalline properties of the amphiphilic materials have also been characterized. Stable hydrogels at room temperature have been obtained and the fibrillar supramolecular structures formed by the self-assembly have been studied by different microscopic techniques on the dried gel (xerogel) and hydrated conditions in order to characterize the micro- and nanostructures. Self-assembly gives rise to supramolecular ribbons with a torsion that is related to a chiral supramolecular arrangement of amphiphiles. The formation of an opposite helical arrangement of the ribbons has been found to depend on the sugar polar head. This fact was confirmed by circular dichroism (CD). © 2012 American Chemical Society. Source

Delbaere S.,University of Lille Nord de France | Vermeersch G.,University of Lille Nord de France | Micheau J.-C.,CNRS Laboratory for Molecular and Photochemical Reactions
Journal of Photochemistry and Photobiology C: Photochemistry Reviews | Year: 2011

The good understanding of a photochromic reaction mechanism requires the establishment of the list of all the transient species and the definition of their connecting processes. The purpose of kinetic studies is the determination of the main photochromic parameters, such as the quantum yields of photoisomerization, rate constants of thermal relaxation and spectra of transient species. These data allow the establishment of structure properties relationships in order to select the best substituents to improve photochromic performances within a given series. In this review, we describe the dynamic behaviour of various photochromic systems during thermal relaxation after irradiation, from the simplest mono-exponential decay to the more complicated multi-exponential dynamics. Then, we analyse the evolution of the long-lived isomers under continuous irradiation. Several pedagogical examples and tricks to perform easy kinetic analysis are given in the appendices. © 2011 Elsevier B.V. Source

Pimienta V.,CNRS Laboratory for Molecular and Photochemical Reactions | Antoine C.,University Pierre and Marie Curie
Current Opinion in Colloid and Interface Science | Year: 2014

Surface tension gradients are at the origin of the self-motion and deformation of millimeter-sized floating objects. For (quasi-)non-deformable systems, like solids and gels, the motion-mode is mainly controlled by the shape of the object and by the way the surface active propellant is released on the surrounding surface. Two situations are reviewed. In the first one, the propellant container is the propelled object itself, while in the second case the propellant is placed in a reservoir embarked on a manufactured float. The properties and efficiency of these solid systems are examined and compared for different geometries. They are also compared with the intriguing properties of self-motile liquid lenses/drops which present several additional abilities (spontaneous deformation to adapt their shape to the selected motion-mode, presence of complex fluid flows outside and inside the drops, partial break-ups. . .). Three mechanisms leading to spontaneous motility have been identified in the literature. Among them two are more largely exemplified in the following as they involve a contribution of the "Marangoni driven spreading" effect, leading to velocities on the cm/s scale. The main theoretical tools usually used for describing the motion and deformation of such self-propelled systems are also reviewed. © 2014 Elsevier Ltd. Source

Harrisson S.,CNRS Laboratory for Molecular and Photochemical Reactions | Nicolas J.,CNRS Galen Institute
ACS Macro Letters | Year: 2014

The rate constants of activation and termination were determined for SET-LRP/SARA-ATRP polymerizations of methyl acrylate. Measurement of the rate of generation of CuBr2 throughout the reaction (using data from Levere et al., Macromolecules 2012, 45, 8267-8274) allowed evaluation of the chain length dependence of the two rate constants, which were found to be 1.25(9) × 10-4DPn -0.51(3) cm·s -1 (activation) and 3.1(1) × 109DPn -0.49(2) L·mol-1·s-1 (termination). Addition of the CuBr2 deactivator at the beginning of the reaction is found to result in a higher proportion of dead chains due to rapid termination of short chains. © 2014 American Chemical Society. Source

Palleau E.,INSA Toulouse | Sangeetha N.M.,INSA Toulouse | Viau G.,INSA Toulouse | Marty J.-D.,CNRS Laboratory for Molecular and Photochemical Reactions | Ressier L.,INSA Toulouse
ACS Nano | Year: 2011

We present a simple protocol to obtain versatile assemblies of nanoparticles from aqueous dispersions onto charge patterns written by atomic force microscopy, on a 100 nm thin film of polymethylmethacrylate spin-coated on silicon wafers. This protocol of nanoxerography uses a two-stage development involving incubation of the desired aqueous colloidal dispersion on charge patterns and subsequent immersion in an adequate water-soluble alcohol. The whole process takes only a few minutes. Numerical simulations of the evolution of the electric field generated by charge patterns in various solvents are done to resolve the mechanism by which nanoparticle assembly occurs. The generic nature of this protocol is demonstrated by constructing various assemblies of charged organic/inorganic/metallic (latex, silica, gold) nanoparticles of different sizes (3 to 100 nm) and surface functionalities from aqueous dispersions onto charge patterns of complex geometries. We also demonstrate that it is possible to construct a binary assembly of nanoparticles on a pattern made of positive and negative charges generated in a single charge writing step, by sequential developments in two aqueous dispersions of oppositely charged particles. This protocol literally extends the spectra of eligible colloids that can be assembled by nanoxerography and paves the way for building complex assemblies of nanoparticles on predefined areas of surfaces, which could be useful for the elaboration of nanoparticle-based functional devices. © 2011 American Chemical Society. Source

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