Simplified silica (Zeosil 1165 MP) and SBR (140k carrying silanol end-groups) nanocomposites have been formulated by mixing of a reduced number of ingredients with respect to industrial applications. The thermo-mechanical history of the samples during the mixing process was monitored and adjusted to identical final temperatures. The filler structure on large scales up to micrometers was studied by transmission electron microscopy (TEM) and very small-angle X-ray scattering (SAXS). A complete quantitative model extending from the primary silica nanoparticle (of radius ≈10 nm), to nanoparticles aggregates, up to micrometer-sized branches with typical lateral dimension of 150 nm is proposed. Image analysis of the TEM-pictures yields the fraction of zones of pure polymer, which extend between the branches of a large-scale filler network. This network is compatible with a fractal of average dimension 2.4 as measured by scattering. On smaller length scales, inside the branches, small silica aggregates are present. Their average radius has been deduced from a Kratky analysis, and it ranges between 35 and 40 nm for all silica fractions investigated here (Φsi = 8−21% vol.). A central piece of our analysis is the description of the interaggregate interaction by a simulated structure factor for polydisperse spheres representing aggregates. A polydispersity of 30% in aggregate size is assumed, and interactions between these aggregates are described with a hard core repulsive potential. The same distribution in size is used to evaluate the polydisperse form factor. Comparison with the experimental intensity leads to the determination of the average aggregate compacity (assumed identical for all aggregates in the distribution, between 31% and 38% depending on Φsi), and thus aggregation number (ca. 45, with a large spread). Because of the effect of aggregate compacity and of pure polymer zones, the volume fraction of aggregates is higher in the branches than Φsi. The repulsion between aggregates has a strong effect on the apparent isothermal compressibility: it leads to a characteristic low-q depression, which cannot be interpreted as aggregate mass decrease in our data. In addition, the reinforcement effect of these silica structures in the SBR-matrix is characterized with oscillatory shear and described with a model based on the same aggregate compacity. Finally, our results show that it is possible to analyze the complex structure of interacting aggregates in nanocomposites of industrial origin in a self-consistent and quantitative manner.

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.

Very long and thin monocrystalline Pd nanowires were synthesized by decomposition using hydrazine vapour treatment of Pd2(DBA)3 confined in the oil phase of a hexagonal mesophase. The mesophase is composed of toluene-swollen tubes, doped with the Pd precursor, stabilized by a monolayer of surfactant and cosurfactant molecules, and arranged on a triangular lattice in water. Our synthesis is selective and the experiments show that both the confinement and the nature of the surfactant are essential to obtain these Pd nanowires.

We report a demonstration of phase-resolved vibrometry, in which out-of-plane sinusoidal motion is assessed by heterodyne holography. In heterodyne holography, the beam in the reference channel is an optical local oscillator (LO). It is frequency-shifted with respect to the illumination beam to enable frequency conversion within the sensor bandwidth. The proposed scheme introduces a strobe LO, where the reference beam is frequency-shifted and modulated in amplitude, to alleviate the issue of phase retrieval. The strobe LO is both tuned around the first optical modulation side band at the vibration frequency, and modulated in amplitude to freeze selected mechanical vibration states sequentially. The phase map of the vibration can then be derived from the demodulation of successive vibration states.

An analytical and numerical study of the linear Saffman-Taylor instability for a Maxwell viscoelastic fluid is presented. Results obtained in a rectangular Hele-Shaw cell are complemented by experiments in a circular cell corroborating the universality of our main result: The base flow becomes unstable and the propagating disturbances develop into crack-like features. The full hydrodynamics equations in a regime where viscoelasticity dominates show that perturbations to the pressure remain Laplacian. Darcy's law is expressed as an infinite series in the cell thickness. An unique dimensionless parameter Delta-bar, equivalent to a relaxation time, controls the growth rate of the perturbation. Delat-bar depends on the applied gradient of pressure, the surface tension, the cell thickness, and the elastic modulus of the fluid. For small values of Delta-bar, Newtonian behavior dominates whereas for higher values of Delta-bar viscoelastic effects appear. For the critical value Dalta-bar ~= 10 a blowup is predicted and fracture-like patterns are observed.

Designing synthetic microenvironments for cellular investigations is a very active area of research at the crossroads of cell biology and materials science. The present work describes the design and functionalization of a three-dimensional (3D) culture support dedicated to the study of neurite outgrowth from neural cells. It is based on a dense self-assembled collagen matrix stabilized by 100-nm-wide interconnected native fibrils without chemical crosslinking. The matrices were made suitable for cell manipulation and direct observation in confocal microscopy by anchoring them to traditional glass supports with a calibrated thickness of ∼50μm. The matrix composition can be readily adapted to specific neural cell types, notably by incorporating appropriate neurotrophic growth factors. Both PC-12 and SH-SY5Y lines respond to growth factors (nerve growth factor and brain-derived neurotrophic factor, respectively) impregnated and slowly released from the support. Significant neurite outgrowth is reported for a large proportion of cells, up to 66% for PC12 and 49% for SH-SY5Y. It is also shown that both growth factors can be chemically conjugated (EDC/NHS) throughout the matrix and yield similar proportions of cells with longer neurites (61% and 52%, respectively). Finally, neurite outgrowth was observed over several tens of microns within the 3D matrix, with both diffusing and immobilized growth factors.

Diblock copolymers of styrene and gelable acryloxy propyl triethoxysilane (APTES) were successfully prepared through Nitroxide-Mediated Polymerization (NMP). Their micellar behaviour in dioxane-methanol solutions was investigated by Small Angle X-ray Scattering (SAXS) and Neutron Scattering (SANS) measurements. The micelles were found to be spherical whatever the copolymer composition with a PS core size varying from 13.5 nm to 37.8 nm depending on the PS chain length and the swelling ratio. The thickness of the PAPTES corona increased from 6.0 nm to 10.8 nm when increasing the PAPTES polymerization degree from 91 to 336. Two micellar structural regimes were identified, depending on the chain length of the PAPTES soluble block. For PAPTES polymerization degrees higher than 100, the PS core radius in dried state RDC can be consistently described by a scaling relationship RDC α (NPS0.34NPAPTES−0.069) and the aggregation number Nagg obeys the relationship Nagg α (NPS0.021NPAPTES−0.21), consistent with previous studies. For polymerization degrees of the soluble block lower than 100, it was shown that RDC and Nagg do not follow the expected scaling relationships with higher values of Nagg, possibly due to complete chain incorporation in the micelle core. After the cross-linking process, a decrease of the hydrodynamic diameter of 1.6 to 4.7 nm was observed. This is mainly due to the corona shrinkage, the aggregation number and the core radius being directly dependent of the parent non-crosslinked micelles.