Eur. Phys. J. E (2015) 38: 88
https://doi.org/10.1140/epje/i2015-15088-1

Regular Article

Structural and multi-scale rheophysical investigation of diphasic magneto-sensitive materials based on biopolymers

¹ UPMC Univ Paris 06, CNRS, Lab. PHENIX, Case 51, Sorbonne Universités, 4 place Jussieu, F-75005, Paris, France
² Matière et Systèmes Complexes (MSC) UMR 7057 CNRS & Université Paris Diderot-Paris 7, Bâtiment Condorcet Case 7056, 75205, Paris Cedex 13, France

^* e-mail: alain.ponton@univ-paris-diderot.fr

Received: 25 March 2015
Revised: 2 July 2015
Accepted: 10 July 2015
Published online: 14 August 2015

Abstract

We present a structural and a multi-scale rheophysical investigation of magneto-sensitive materials based on biopolymers, namely aqueous solutions of sodium alginate incorporating magnetic maghemite nanoparticles, functionalized with adsorbed negative citrate ions. The large alginate ionic strength impacts the structure and the rheology of these nanocomposites in zero magnetic field. In given physico-chemical conditions, the system is fluid and homogeneous on macroscopic scales while it is diphasic on microscopic ones, containing micro-droplets coming from the demixion of the system. These micro-droplets are liquid and deformable under magnetic field. Their under-field elongation and their zero-field relaxation are directly observed by optical microscopy to determine their interfacial tension, their magnetic susceptibility and their internal viscosity. A structural analysis of the solutions of alginate chains and of the phase-separated mixtures of alginate and nanoparticles by Small Angle Scattering completes the local description of the system.