DOI: 10.1021/cm301083r
WoS: 000307988800005
61 Citations
Résumé:

Sol-gel syntheses involving either neutral water or formic acid as a reactant have been investigated (1) to determine the best conditions to confine a maximum of ionic liquid (IL) inside silica-based matrixes and (2) to reach the highest porosity after removing the IL from the ion gels (washed gels). Several sets of ionogels were prepared from various 1-butyl-3-methylimidazolium ILs and various silica or organosilica sources. The study evidenced a critical effect of the anion on the morphology (monolith, powder) and texture of the resulting washed gels. Particularly, tetrafluoroborate anion led to monolith ionogels by a simple hydrolytic method, affording highly condensed mesoporous silicas with some fluorinated surface sites. Such sites have never been reported before and were evidenced by 19F NMR. On the other hand, formic acid solvolysis turned out to be the only method to get non-exuding, crack-free, and transparent monoliths from ILs containing bis(trifluoromethylsulfonyl)imide [NTf2] anion, with promising applications in photochemistry or photosensing. With bulky imidazolium and pyridinium cations, removal of the IL led to highly porous silicas with pore diameters and pore volumes as high as 10–15 nm and 3 cm3 g–1, respectively. These silicas could find applications as supports for immobilizing bulky molecules.

Ref HAL: hal-00762379_v1
Ref Arxiv: 1212.1064
DOI: 10.1002/adfm.201200666
WoS: 000312300600006
Ref. & Cit.: NASA ADS
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32 Citations
Résumé:

We use hexagonal mesophases made of oil-swollen surfactant-stabilized tubes arranged on a triangular lattice in water and doped with metallic salts as templates for the radiolytic synthesis of nanostructures. The nanostructures formed in this type of soft matrix are bimetallic palladium-platinum porous nanoballs composed of 3D-connected nanowires, of typical thickness 2.5 nm, forming hexagonal cells. We demonstrate using electron microscopy and small-angle X-ray scattering that the pore size of the nanoballs is directly determined by the diameter of the oil tube of the doped mesophases, which we have varied in a controlled fashion from 10 to 55 nm. Bimetallic nanostructures comprising various proportions of palladium and platinum can be synthesized. Their alloy structure was evidenced by X-ray photoelectron spectroscopy, energy-dispersive X-ray spectroscopy, and high-angular dark field scanning transmission electron microscopy experiments. Our templating approach allows therefore the synthesis of bimetallic nanoballs of tunable porosity and composition.

Commentaires: Journal: Advanced Functional Materials 22, 4900 (2012)

Ref HAL: hal-00683723_v1
PMID 22422291
DOI: 10.1039/c2cp40250e
WoS: 000302062200038
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18 Citations
Résumé:

The crystalline structure of ureidopyrimidinone-based silane (UPY) has been determined. The local and long range order structuring of the bridged silsesquioxane (MUPY) resulting from the sol-gel hydrolysis-condensation of the former precursor has been investigated by MFTIR (Mid Fourier Transform InfraRed) combined with DFT (Density Functional Theory) and XRD (X-ray diffraction) studies. These studies showed that a long range structuring exists within the organic fragments with the transcription of the DDAA (Donor-Donor-Acceptor-Acceptor) H-bonding array from UPY to MUPY whereas a disordered siloxane network was revealed in the hybrid material.

Ref HAL: hal-00628223_v1
DOI: 10.1103/PhysRevLett.107.148302
WoS: 000296285800029
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13 Citations
Résumé:

We study the nonlinear rheology of a novel class of transient networks, made of surfactant micelles of tunable morphology reversibly linked by block copolymers. We couple rheology and time-resolved structural measurements, using synchrotron radiation, to characterize the highly nonlinear viscoelastic regime. We propose the fluctuations of the degree of alignment of the micelles under shear as a probe to identify a fracture process. We show a clear signature of a brittle-to-ductile transition in transient gels, as the morphology of the micelles varies, and provide a parallel between the fracture of solids and the fracture under shear of viscoelastic fluids.

Résumé:

We report on a new class of self−assembled transient networks made of surfactant micelles of tunable morphology (from spheres, to rodlike to wormlike) reversibly linked by telechelic polymers. Linear rheological measurements show that three distinct domains can be defined depending on the morphologies of the micelles: a domain where the micelles are isolated and not entangled, an intermediate domain where the micelles are partially entangled and a domain where the micelles are fully entangled. Flow curves of the transient networks of tunable morphology associated with structural informationjs obtained from Rheo−SAXS suggest that one can associate to the three domains distinct failures modes: a brittle mode, an intermediate mode and finally a ductile/shear banding mode, as the micelles grow. The ultimate goal is to elucidate the parameters that drive the transition

Ref HAL: hal-00572408_v1
PMID 21300368
DOI: 10.1016/j.jcis.2011.01.055
WoS: 000288527800034
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15 Citations
Résumé:

We report the synthesis of novel chiral catanionic liquid crystals bearing camphorsulfonamide substructures. The phase behaviour of these long-chain substituted imidazolium sulphates and sulfonates was investigated using X-ray diffraction (XRD), polarizing optical microscopy (POM) and differential scanning calorimetry (DSC). We observed that the phase behaviour clearly depends on the substitution of both cation and anion. The chiral camphorsulfonamide substructures have an unfavourable influence on the formation of liquid crystalline (LC-) phases. Contrary to N,N0-di-alkyl-imidazolium salts, the formation of LC phases was only observed when both cation and anion are substituted with long alkyl chains (C12 or C16). Furthermore, the phase transition temperatures depend on the chain length of the alkyl groups, as higher phase transition temperatures were observed for compounds bearing longer alkyl chains. However, no macroscopic evidence for the formation of chiral mesophases was obtained.

Ref HAL: hal-01224601_v1
DOI: 10.1039/C0DT00583E
WoS: 000283740500003
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21 Citations
Résumé:

A series of gold- and silver-containing ionic liquids, [CnMIM][M(CN)2] (M = Au, Ag; n = 12, 14, 18), prepared by metathesis reactions, present luminescence depending on their physical state i.e. crystalline or smectic A phases. The photoluminescent measurements as well as DFT calculations suggest that the modulation of aurophilic intermolecular interactions are responsible for this phosphorescent behaviour.