Physico-chimie des Polymères et des Milieux Dispersés
Sciences et Ingénierie de la Matière Molle

Chimie supramoléculaire : un outil de choix pour l'élaboration d'assemblages macromoléculaires multi-stimulables.

Antoine CHATEAUMINOIS — 2010-09-30T12:50:00Z

jeudi 30 septembre 2010 - Amphi Joliot

Rinse and Repeat : Turning liquids into soft adhesives

Antoine CHATEAUMINOIS — 2010-09-28T10:30:00Z

This paper describes “rinsing flows” wherein a jet of one fluid ablates a layer of a second, miscible liquid that coats a solid substrate. This process is common to everyday experience and to many industrial processes, particularly cleaning operations. This flow arrangement is accompanied by a classic, “hydraulic jump” phenomenon but the stratification of two liquids, with differing rheologies, leads to qualitatively new results. Of particular interest to one of the applications of this process (the cleaning of colloidal particles from solid, planar substrates) is the case when the liquid coating the substrate (the one being rinsed off) possesses a large elongational viscosity. Data are offered that demonstrate that fluids with large, strain thickening extensional viscosities very effectively “pluck” adsorbed colloidal particles from planar surfaces.

Surfactant adsorption and formation of microemulsion nanocomposites.

Antoine CHATEAUMINOIS — 2010-09-16T13:42:00Z

Jeudi 23 septembre - 14h00 Amphi Joliot

- Séminaires à venir

Tracer diffusion of particles in gels

Antoine CHATEAUMINOIS — 2010-09-16T12:46:00Z

We have determined the mean square displacement of spherical particles in globular protein gels using confocal scanning light microscopy. The displacement of particles with different sizes was correlated to the structure of the protein gels. The latter depended strongly on the strength of the electrostatic interactions. In parallel we have studied the diffusion of hard spheres in model particle gels by numerical simulations. The relevance of these simulations to the diffusion of particles in globular protein gels will be discussed.

Rheo-optic and rheo-NMR studies of the flow behaviour of wormlike micelles solutions

Antoine CHATEAUMINOIS — 2010-09-09T10:03:00Z

In the appropriate conditions surfactant molecules in solution may self-assemble into long semi-flexible polymer-like rods called wormlike micelles. Wormlike micelles solutions can show pronounced viscoelasticity and are sometime observed to flow in a peculiar way that suggests that the viscosity of the fluid varies discontinuously. This discontinuous banding has generated considerable interest because of its general implications for the flow behaviour of complex fluids. Despite years of study the underlying mechanism for this flow instability is still not well understood. Here I report on our recent investigations into the flow behaviour of semi-dilute wormlike micelles solutions composed of the surfactant cetylpyridinium chloride (CPCl) and counterion sodium salicylate (NaSal) in brine ([CPCl]/[NaSal]=2, variable weight fraction, in [NaCl]=0.5 M brine) using rheo-optical technique based on homodyne photo-correlation spectroscopy (PCS), diffusing wave spectroscopy (DWS), ellipsometry and direct observation along with rheo-nuclear magnetic resonance (NMR) and conventional mechanical rheometry. Partitioning into stable high viscosity/low shear rate/high birefringence/low turbidity and low viscosity/high shear rate/low birefringence/high turbidity bands was observed in strongly shear-thinning samples in a cylindrical-Couette flow cell geometry using a combination of PCS and ellipsometry. Stable shear banding was also demonstrated in strongly shear thinning samples in the cylindrical-Couette geometry using DWS – DWS measurements suggested that unstable shear flow may be present in the parallel-plate flow geometry. Fluctuating turbid rings were observed directly in strongly shear thinning samples in the parallel-plate geometry – subsequent rheo-NMR measurements indicated that these rings were correlated with formation of a fluctuating high strain band (Fig. 1).

Fig 1. Sequence of transverse rheo-NMR velocity and shear rate images showing shear banding of a wormlike micelles solution in the parallel-plate geometry (r=10 mm, d=0.75 mm).

Applying Soft Materials to Real World Problems.

Antoine CHATEAUMINOIS — 2010-09-07T08:33:00Z

The Complex Assemblies of Soft Matter Lab (COMPASS UMI 3254) is a unique collaboration between the CNRS, Rhodia and the University of Pennsylvania. The COMPASS lab is a team of scientists with differentiating capabilities in the creation, manipulation and understanding of soft materials. The team is dedicated to finding sustainable innovative solutions to real world problems. The three main themes of the lab are water scarcity, energy storage and transfer, and sustainable formulations. In this talk, an overview of the activities will be presented. 1) Water Scarcity : The goal of this project is to increase the amount water available to roots of crops and reduce overall water consumption. Studies will be presented on flow in fragile porous media, clogging mechanisms and root growth in the presence of drainage and evaporation. 2) Energy Transfer and Storage : Studies will be presented on new formulations based on organic components that are good candidates for the replacement of Indium Tin Oxide. In addition, studies will be presented on catalytic inks for the reduction of platinum in fuel cell devices. 3) Sustainable Formulations : Studies will be presented based on a unique novel system, temperature sensitive microgels. These microgels are used to understand jamming and melting behavior in real time. This model system allows us to better understand space filling mechanisms in formulations with the goal of achieving equal performance with the minimum amount of raw materials.

De nouveaux étudiants au PPMD

Armand Hakopian — 2010-09-03T14:27:32Z

Comme chaque année à l'automne, de nouveaux étudiants rejoignent le PPMD. Nous accueillons ainsi, Étienne Ducrot, Lucie Besnard, Peiluo Shi, Solenn Moro et Basile Pottier qui commencent leur travail de thèse.

Analysis of 2D relaxation exchange NMR

Armand Hakopian — 2010-08-25T21:20:30Z

Two-dimensional (2D) relaxation exchange NMR is a form of 2D nuclear magnetic resonance (NMR) where molecular motion and transport are mapped by relaxation exchange...

- A la une

Analysis of 2D relaxation exchange NMR

VAN LANDEGHEM Maxime — 2010-08-25T15:20:58Z

Maxime Van Landeghem, Jean-Baptiste d'Espinose

Two-dimensional (2D) relaxation exchange NMR is a form of 2D nuclear magnetic resonance (NMR) where molecular motion and transport are mapped by relaxation exchange. This NMR technique is now gaining momentum in a wide variety of applications involving wetting and drying of liquids in porous media. This experiment is analogous to 2D frequency exchange NMR but appears more appropriate for the study of the exchange of liquids between pores because relaxivity is expected to depend on pore size, whereas the chemical shift is not.

Simulation was used to fully understand the behaviour of multi-site correlation maps and extract from the experiment the unbiased exchange parameters which are the meaningful parameters.

M. Van Landeghem, A. Haber, J-B. d'Espinose de Lacaillerie, B. Blümich, Concepts in Magnetic Resonance part A 2010, 36A(3), 153-169, “Analysis of Multisite Relaxation Exchange NMR”

Non linear rheology of model filled elastomers

PAPON Aurélie — 2010-08-25T15:17:59Z

Submitted to large sinusoidal strains, filled elastomers show not only a decrease in their storage modulus - the Payne effect, but also a non linear behavior - their response is not sinusoidal anymore and involves strain-stiffening. We show in this study that the two effects can be separated thanks to Large Amplitude Oscillatory Shear experiments.

The introduction of solid particles such as silica or carbon black in elastomer matrix is a very standard procedure in the tire industry. It greatly improves the mechanical properties of the rubber but also introduces a non linear behavior. One example of this complex behavior is the well-known Payne effect : whereas unfilled elastomers exhibit a constant elastic modulus for strain amplitudes up to 100% during cyclic strain experiments, filled rubbers show a significant decrease in their elastic modulus for strain amplitudes typically from a few percents. It is often assumed that in this strain domain, filled elastomers exhibit a quasi-harmonic behavior. It means that under sinusoidal solicitation, they have a quasi-sinusoidal response.

We show that for our model filled samples however the non linearity in the response is significant : a large sinusoidal strain gives rise to a non sinusoidal stress. We analyzed the stress signal in two steps : first the decomposition into elastic and viscous parts and then the extraction of a linear and a non-linear contribution in each part. The modulus given by the rheometer corresponds to the sum of the two components. The non linear contribution is not negligible from strain amplitudes of around 10% in our samples.

We show that the strain-stiffening is correlated with the Payne effect but also most probably has its origins in the finite extensibility of the polymer chains confined between solid particles, where the strain is larger. We also point out that the samples behave differently whether the grafting agent used creates a covalent bond between the silica and the polymer or not.

A. Papon, H. Montes, F. Lequeux and L. Guy. Non linear rheology of model filled elastomers, Journal of polymer science Part B : Polymer physics, in press.


Elastic stress as a function of strain: In the linear regime, the elastic stress plotted as a function of the strain inside one cycle of solicitation is a straight line with a slope G'. Here we can see a deviation from the straight line : there is an intra-cycle strain-hardening, similar to a finite extensibility phenomenon. Moreover, the slope at the origin is decreasing with the strain amplitude : this is the Payne effect.


Storage modulus decomposition into a linear and a non linear contribution: Fitting the elastic stress as function of strain with a polynomial function, we can extract a linear and a non-linear contribution in the storage modulus. From strain amplitudes of 10%, the two contributions are superimposed and the rheometer is only giving the sum of the two.

Physico-chimie des Polymères et des Milieux Dispersés Sciences et Ingénierie de la Matière Molle

Chimie supramoléculaire : un outil de choix pour l'élaboration d'assemblages macromoléculaires multi-stimulables.

Rinse and Repeat : Turning liquids into soft adhesives

Surfactant adsorption and formation of microemulsion nanocomposites.

Tracer diffusion of particles in gels

Rheo-optic and rheo-NMR studies of the flow behaviour of wormlike micelles solutions

Applying Soft Materials to Real World Problems.

De nouveaux étudiants au PPMD

Analysis of 2D relaxation exchange NMR

Analysis of 2D relaxation exchange NMR

Non linear rheology of model filled elastomers

Physico-chimie des Polymères et des Milieux Dispersés
Sciences et Ingénierie de la Matière Molle