J.-F. Berret

Fluorocarbon associative polymers

Fluorocarbon associative polymers modified along the backbone or at the extremities by hydrophobic groups are reviewed with respect to their association and rheological properties in aqueous solutions. Above a threshold concentration corresponding to the formation of a reversible network structure, the solutions behave as physical gels. In this review, it is shown that the viscoelasticity of fluorocarbon associative polymer gels is enhanced with respect to that of hydrocarbon analogues. For polymers substituted at the extremities (telechelics), significant progresses have been made in recent years concerning the microstructure, the phase behavior and the rheology of the gel state. Telechelics in solutions are forming multiconnected structures, which dynamical features are in good agreement with those of transient network models.

SHEAR-INDUCED ISOTROPIC-TO-NEMATIC PHASE TRANSITION IN EQUILIBRIUM POLYMERS

We report on a first-order isotropic-to-nematic phase transition induced by shear in concentrated solutions of elongated flexible wormlike micelles. As shear is applied to a disordered micellar solution, the transition shows up in steady-shear experiments as a kink in the shear stress behaviour. Using small-angle neutron scattering under shear, we show that beyond the transition rate, a nematic phase manifests itself by the growth of crescentlike scattering patterns in the direction perpendicular to the flow. A dynamical phase diagram is finally proposed for this system of equilibrium polymers.

How Universal are the Low Temperature Acoustic Properties of Glasses

AbstractWe evaluated already published data on ultrasound absorption and velocity changes below 1 K for a set of 18 different glasses. By uniformly analysing these data according to the tunnelling model we have calculated the standard spectral density

Time scales in shear banding of wormlike micelles

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Rheology and nuclear magnetic resonance measurements under shear of sodium dodecyl sulfate/decanol/water nematics

of two-level-systems (TLS) and their coupling energyγ1 andγ1 to longitudinal and transversal phonons. Contrary to literature, we have not observed any correlation between

Stabilization and controlled association of inorganic nanoparticles using block copolymers

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