suspensions of SOft CApsules – SOCA

Compartmentalization is an efficient way to protect, convey and deliver molecules of interest and to elaborate innovative multiphasic materials. A striking example is the microcapsule, µCP, a droplet bounded by a viscoelastic sheet playing the role of barrier. During fabrication and in many applications, µCPs are not isolated species and flow with many others. The behaviour of such suspensions is largely unknown today and its use is more a matter of know-how than a deep knowledge of the interfacial mechanisms involved.

By a multidisciplinary approach associating the polymer chemistry, the experimental physics of µCPs and the numerical simulations, SOCA will study the rheology of suspensions of soft µCPs and their structure under flow. The salient feature is the role of deformability which can be extreme, more than 100 %, without any plastic event contrary to solid particles and gel beads. SOCA aims at the fundamental and thorough study of the viscosity of suspensions in respect of the volume fraction of µCPs up to the jamming transition with tuned local interactions (friction and colloidal forces up to adhesion) and in a large range of viscous stress. To gain insight in the dynamics to reach the out-of-equilibrium structure, SOCA will study the density profile in suspensions flowing in ducts and the variations of shapes by tracking tailored fluorescently-tagged µCPs.
To do so, SOCA will develop a library of tailored µCPs with controlled structural parameters (diameter, dispersity, roughness of the µCPs and chemical structure, thickness of the shell) and relevant properties (Tg, cross-link density, entanglement, friction/adhesion and elastic properties of the shell). The constant feedback between experimental results and numerical simulations with various models of local forces will be a key point notably in the limits of large deformations and/or high capsule volume fraction to understand what effects prevail.