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-00569378_v1
Ref Arxiv: 1102.5172
DOI: 10.1103/PhysRevLett.106.118302
WoS: 000288326700015
Ref. & Cit.: NASA ADS
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45 Citations
Résumé:

We use a combination of original light scattering techniques and particles with unique optical properties to investigate the behavior of suspensions of attractive colloids under gravitational stress, following over time the concentration profile, the velocity profile, and the microscopic dynamics. During the compression regime, the sedimentation velocity grows nearly linearly with height, implying that the gel settling may be fully described by a (time-dependent) strain rate. We find that the microscopic dynamics exhibit remarkable scaling properties when time is normalized by strain rate, showing that the gel microscopic restructuring is dominated by its macroscopic deformation.

Ref HAL: hal-00565584_v1
DOI: 10.1039/c0sm00863j
WoS: 000287091600027
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54 Citations
Résumé:

We examine the behavior of spherical silica particles trapped at an air-nematic liquid crystal interface. When a strong normal anchoring is imposed, the beads spontaneously form various structures depending on their area density and the nematic thickness. Using optical tweezers, we determine the pair potential and explain the formation of these patterns. The energy profile is discussed in terms of capillary and elastic interactions. Finally, we detail the mechanisms that control the formation of a hexagonal lattice and analyze the role of gravity for curved interfaces.

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.

Ref HAL: hal-00656002_v1
DOI: 10.1038/NMAT2939
WoS: 000287517400025
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115 Citations
Résumé:

Crosslinked and bundled actin filaments form networks that are essential for the mechanical properties of living cells. Reconstituted actin networks have been extensively studied not only as a model system for the cytoskeleton, but also to understand the interplay between microscopic structure and macroscopic viscoelastic properties of network-forming soft materials. These constitute a broad class of materials with countless applications in science and industry. So far, it has been widely assumed that reconstituted actin networks represent equilibrium structures. Here, we show that fully polymerized actin/fascin bundle networks exhibit surprising age-dependent changes in their viscoelastic properties and spontaneous dynamics, a feature strongly reminiscent of out-of-equilibrium, or glassy, soft materials. Using a combination of rheology, confocal microscopy and space-resolved dynamic light scattering, we demonstrate that actin networks build up stress during their formation and then slowly relax towards equilibrium owing to the unbinding dynamics of the crosslinking molecules.

Ref HAL: hal-00549685_v1
Ref Arxiv: 1010.3549
DOI: 10.1103/PhysRevLett.105.199605
WoS: 000283849300024
Ref. & Cit.: NASA ADS
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9 Citations
Résumé:

G. Brambilla et al. Reply to a Comment by J. Reinhardt et al. questioning the existence of equilibrium dynamics above the critical volume fraction of colloidal hard spheres predicted by mode coupling theory.

Commentaires: Reply to a Comment by J. Reinhardt et al. (see arXiv:1010.2891), which questions the existence of equilibrium dynamics above the critical volume fraction of glassy colloidal hard spheres predicted by mode coupling theory

PMID 21231307
DOI: 10.1103/PhysRevLett.105.214301
WoS: 000284308500011
170 Citations
Résumé:

We report observation of Plateau instability in a thin filament of solid gel wit h a very small elastic modulus. A longitudinal undulation of the surface of the cylinder reduces its area thereby triggering capillary instability, but is count erbalanced by elastic forces following the deformation. This competition leads t o a nontrivial instability threshold for a solid cylinder. The ratio of surface tension to elastic modulus defines a characteristic length scale. The onset of l inear instability is when the radius of the cylinder is one sixth of this length scale, in agreement with theory presented here.