Laboratoire Matière et Systèmes Complexes

MSC : A. Ponton, C. Galindo Gonzalez (1) , Y. Yip Cheung Sang (2), M.-A. Guedeau-Boudeville, J.-M. Di Meglio.

Collaborations : A. Bée, R. Perzynski (Laboratoire Physicochimie des Electrolytes, Colloïdes et Sciences Analytiques, UMR 7195 CNRS & Université Pierre et Marie Curie – Paris 6)

 (1)CDD 2 ans financé par la communauté européenne Bourse Marie Curie 7ème PCRD Actions IEF (oct 2009-oct 2011)
 (2)thèse de l’Université Paris Diderot-Paris 7 soutenue en juillet 2009
 financement labex SEAM (déc 2009-mai 2012)

Cellule magnétorhéologique @ MSC, PECSA

This research is concerned with the multiscale study of structural and mechanical properties of new nanocomposite materials based on magneto-stimulable biopolymers produced by introduction of magnetic nanoparticles of maghemite functionalized by adsorption of citrate ions in aqueous solutions of a polysaccharide extracted from marine brown algae (sodium alginate negatively charged in medium of neutral or alkaline pH. The study of flow properties of mixed solutions of sodium alginate / citrated ferrofluids had highlighted the formation of magnetic micronic droplets of demixion which were locally observed in the presence of a controlled and uniform magnetic field of the order of several mT. The interfacial tension and the magnetic susceptibility of the droplets were computed from the analysis of their elongation. The local viscosity was calculated from the relaxation dynamics of droplets after interruption of the magnetic field.

An original experimental set-up of magneto-rheology was built to perform temperature-controlled flow and oscillatory measurements under continuous magnetic field values of maximum 50 mT in the current configuration. We clearly demonstrated for the first time to our knowledge a magneto-viscoelastic effect in biopolymer networks that is manifested by an increase in viscosity at low shear rate and by an increase in linear viscoelastic moduli.

Variation de la viscosité en fonction de la vitesse de cisaillement pour différentes valeurs de champ magnétique d’une solution aqueuse d’alginate (Calg = 18 g.L-1) avec des nanoparticules magnétiques (phiNP = 0,5%). Des observations microscopiques de la solution sont présentées sans champ et avec un champ de 23.4 kA/m (barre: 100 microns).