Crosslinked Elastomers: Structure-Property Relationships and Stress-Optical Law.

We present a combination of independent techniques in order to characterize crosslinked elastomers. We combine well-established macroscopic methods, such as rheological and mechanical experiments and equilibrium swelling measurements, a more advanced technique such as proton multiple-quantum NMR, and a new method to measure stress-induced segmental orientation by in situ tensile X-ray scattering. All of these techniques give access to the response of the elastomer network in relation to the crosslinking of the systems.

Efficient polynomial analysis of magic-angle spinning sidebands and application to order parameter determination in anisotropic samples.

Chemical shift tensors in C solid-state NMR provide valuable localized information on the chemical bonding environment in organic matter, and deviations from isotropic static-limit powder line shapes sensitively encode dynamic-averaging or orientation effects. Studies in C natural abundance require magic-angle spinning (MAS), where the analysis must thus focus on spinning sidebands. We propose an alternative fitting procedure for spinning sidebands based upon a polynomial expansion that is more efficient than the common numerical solution of the powder average.

Competitive Adsorption between a Polymer and Solvents onto Silica.

In polymer nanocomposites, particle-polymer interactions play a key role both in the processing and in the final properties of the obtained materials. Specifically, for silica, because of the surface polarity, surface modification is commonly used to improve the compatibility with apolar polymer matrices in order to prevent agglomeration. In this work, a new way to investigate the polymer-silica affinity and determine dispersibility parameters (HDP) of silica particles in the 3D Hansen space using a solvent approach is proposed.

Dielectric relaxation of thin films of polyamide random copolymers.

We investigate the relaxation behavior of thin films of a polyamide random copolymer, PA66/6I, with various film thicknesses using dielectric relaxation spectroscopy. Two dielectric signals are observed at high temperatures, the α process and the relaxation process due to electrode polarization (the EP process). The relaxation time of the EP process has a Vogel-Fulcher-Tammann type of temperature dependence, and the glass transition temperature, T(g), evaluated from the EP process agrees very well with the T(g) determined from the thermal measurements.

Nucleation and Growth of Ordered Copolymer Structures at Reactive Interfaces between PA6 and MA--HDPE.

We have studied the effect of the interfacial chemical reaction between PA6 and MA--HDPE in static conditions at a macroscopically flat interface. Interface destabilization and the growth of instabilities, somehow similar to myelin figures observed in surfactants put in the presence of water, are observed. For the first time in this system, it is shown that ordered microphase-separated copolymer domains, whose morphologies depend on the architecture of the copolymer, namely, essentially on the relative length of the blocks on each side of the interface, may nucleate and grow at a static interface between reactive polymers.

Constrained dynamics in interphases of model filled elastomers: role of interface chemistry on crosslinking, local stress distribution and mechanics.

The Franco-German consortium "DINaFil" (Dynamics at the Interface of Nanoscopic Fillers), located at Paris, Lyon and Halle, and co-funded by the ANR and the DFG, is a multidisciplinary endeavour concerned with a quantitative understanding of the complex behaviour of filled elastomers, a class of daily-life materials with as many uses as fundamentally open questions.