CE06 - Polymères, composites, physique et chimie de la matière molle

Beads Of colloidal Gel Under Stress – BOGUS

Submission summary

Understanding the response of gels under stress is of paramount importance, both fundamentally and in applications. In this general framework, in BOGUS, we will produce unique spherical beads of gel of millimetric size. The gels are based on colloidal particles. They consist in a homogeneous porous stress-bearing network structure, and we will vary in a controlled manner their mechanical properties. Our objective is to rationalize the fate of these beads under stress and to elucidate the complex interplay between the flow of liquid through the pores (the poroelasticity), the plasticity of the network-forming structure and the fracture of the network. We will adopt a multiscale approach that combines mechanical creep under indentation, image analysis, and time- and space-resolved light scattering. Our project is fundamental, but we will mainly investigate two configurations of uttermost relevance in applications, in particular spray drying: the drying/swelling of the beads and their response to an extreme mechanical deformation produced by impact on a solid surface.
To reach a global understanding of the behaviour of beads of gels under stress, the project will be divided into five scientific Tasks. Task1 is devoted to the design and preparation of novel classes of beads of colloidal gel with tuneable properties. We propose several strategies based on the variation of the interactions between the particles, or the softness of the particles or on mixing polymer and colloidal gels, to tune the toughness and the brittleness of the gels. The mechanical behaviour of the different classes of gels in the linear and up to the non-linear regime will be investigated using indentation techniques (Task2). Tasks 3 and 4 are devoted to the characterization of the behaviour of the different types of beads when they are submitted to moderate (Task3) or extreme (Task4) stresses. In Task3, drying, swelling, and eventually several cycles of drying and swelling, will be investigated in a multiscale approach, gathering macroscopic structural information on the instabilities developed by the bead and microscopic dynamic information on the rearrangements of the colloid forming the stress-bearing network structure. In Task4, we will investigate how the beads of gel behave upon impact on a repellent surface Macroscopic information on the fragmentation process undergone by the beads will be acquired here, but on a drastically different regime as the one explored in the drying/swelling protocol, as poroelasticity does not play any role due to the very short time scale of the experiment. Finally, Task5 aims at providing a rationalization of the behaviour of beads of gel under stress as a function of the linear and non-linear mechanical properties of the gels. In addition, one also includes a coordination Task (Task0) to ensure the smooth and efficient progress of the project.
The consortium gathers two experimental teams with complementary expertise in the design and mechanics of soft matter systems, and in mechanical instabilities and physics of drying

Project coordination

Laurence Ramos (Laboratoire Charles Coulomb)

The author of this summary is the project coordinator, who is responsible for the content of this summary. The ANR declines any responsibility as for its contents.

Partner

L2C Laboratoire Charles Coulomb
FAST Fluides, Automatique et Systèmes Thermiques

Help of the ANR 381,889 euros
Beginning and duration of the scientific project: December 2019 - 48 Months

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