Two-component Functional organOGELs – FOGEL

As stated in the National Strategy for Research report (SNR, Action Plan 2016 , ANR Call), while presenting one of the five priorities of Challenge 3 "Industrial Renewal" (Priority 14 "Design of new materials"): " The products of the future will be more complex and mix several materials endowing final products with unique advantages (lightness, conductivity, ….). Combinations of basic components are becoming increasingly diverse. The forming and implementation processes of multi-materials … therefore pose a major challenge."
The FOGEL project is precisely proposed in this context, with the ambition to contribute to a better understanding of the phenomena guiding the structuring process of self-assembled architectures, based on a specific family of donor-acceptor two-component organogels. Organogels constitute a fascinating class of materials prepared through a bottom-up approach. These systems are indeed able to transduce a recognition phenomenon occuring at the molecular level, into a macroscopic network of well-defined one-dimensional entangled assemblies. These materials, based on the self-assembly of organic molecules (gelators) in a given solvent, have been subject to intensive studies, which are justified by reasonably simple syntheses of precursors, a good modularity and an easy implementation. Whereas they have been successfully applied in various areas, they nevertheless suffer from several handicaps which have notably hampered their use in the rapidly expanding field of organic electronics (photonics). On the one hand, rationalization of the gelation capacity of a given system is extremely delicate; secondly, they rely on assemblies which present defects which strongly affect their performance for electronic applications.
In this context, spectacular breakthroughs were accomplished in the last few years, following an approach that is based on donor-acceptor (D-A) two-component organogels. The latter offer the possibility of combining both the intrinsic properties of both entities (e.g. optical / electronic), while relying on their D-A complementarity to generate a self-assembly by charge transfer. We recently described (2016) the preparation of systems based on this approach, by using organogelators featuring two or three photoactive pyrene (D) units. A considerable increase of the gelation capacity of one of these organogelators could be observed upon addition of various acceptors (A) and, remarkably, this effect could be observed for very low ratio of A/D, suggesting an original supramolecular polymerization process, still unknown for this class of gelators. Based on this innovative result, we propose to address through the FOGEL project, a comprehensive study covering the various facets of this very promising new approach. In particular, FOGEL will concentrate on the foundations guiding the nucleation and growth processes from such D-A gels, at both theoretical and experimental levels. The impact of various parameters (such as the A/D ratio) on their stability, on the morphology of the resulting microstructures and on their mechanical properties will be evaluated in order to optimize their implementation. The latter will allow preliminarily studies of their applicability for detection purposes (nitroaromatic compounds, explosives) as well as for charge transport (conductivity). Finally, these fundamental studies will be reinvested in developing new organogelators, in order to extend the scope of this innovative approach.