Axis III

Development of hierarchically structured materials, with fine control at different scales

This research axis focusses on the development of original methodologies to design new hierarchical three-dimensional materials and/or objects. These 3D hierarchically structured materials will be built from either pre-existing building blocks, or emergent ones obtained from our collegues researchers working in axis I. New properties (optical, electronic, mechanical…) will emerge from both the inherent functionalities of the building blocks and cooperative effects resulting from their assembly. For example, monomers with particular optical, biological or electronic functions can be designed and assembled by thermal or photochemical techniques into complex 3D structures, while metal, metal oxide, ceramic, polymeric nano- or microparticles with controlled shape, composition and surface chemistry can be used to give rise to supercrystals by spontaneous self-assembly. From such approaches, complex materials based on lipids, sugars, proteins, polymers, metals or composites could emerge as nano- or micromaterials useful for drug delivery systems, theranostics, photodynamic therapy, organic electronic devices or targeting, as well as larger materials for applications such as prosthesis, implants or catheters. In all these examples, the challenge is to control the morphology of the final object (outer dimensions, shape, texture), its inner structure (composition, homogeneity, gradients, spatial distribution of charges….) and to integrate the materials into functional devices.

Subtheme 1 : Innovative fabrication methods

Multiple research groups have developed innovative fabrication methods, such as self-assembly methodologies, layer-by layer assembly, photopolymerization, high temperature brushing and templating. A synergy has been created between these groups to favor the emergence of new fabrication strategies for the design of functional materials and/or objects. One important strategy consists in combining various methods via both top-down and bottom-up approaches to address the control of fabrication at different scales. In this respect, we will explore approaches such as templating methods (surfactant templating, casting, microporous polymer templating, colloidal crystal templating and bioinspired process, i.e. biotemplating), conventional techniques (supercritical fluids, emulsion, freeze-drying, breath figures, selective leaching, phase separation, zeolitization process, and replication) and basic methods (sol–gel controlling and post-treatment), since they also control the surface and interface properties.

Subtheme 2 : Novel characterization techniques

The increased complexity of multicomponent, hierarchically structured and functional materials requires the development of new characterization techniques to explore the structure and the properties of the material at different length scales. To this end, advanced characterization techniques will be used, including 3D tools (3D tomographic analyses), in situ X-ray nanotomography, mechanical tests or 3D tomography by transmission electron microscopy under environmental conditions. When necessary, these techniques will be improved on or new techniques will be developed. Particular attention is paid to the fate of the elementary building blocks in the edifice and the relationship between the properties of single building blocks and the macroscopic behavior of the final material. In addition to experimental techniques, theoretical approaches, combining all-atom modeling and (soft) condensed matter theories, will be used and further developed to elucidate the correlation between molecular driving forces and the hierarchical assembly of functional materials. Along the same line, molecular simulations will be employed to give microscopic insight into the properties of complex assemblies, such as adsorption processes or viscoelastic behavior. To account for the hierarchical character of the materials multiscale approaches are being developed.