Synthèse et étude de [2]rotaxanes-pillar[5]arènes liquides-cristallins

Mechanically interlocked molecules (MIMs), such as [2]-rotaxanes, are interesting candidates for their inclusion into mesogens due to their unique topological architectures and to the complex nature of their component building blocks. Indeed, combining such unique motion properties of the rotaxanes with the liquid-crystalline molecular order offers an opportunity for the construction of novel smart materials in a dynamic and organized environment with possible applications in catalysis, information transport and sensoring.
In the first place, we have developed an efficient synthesis strategy in order to design [2]rotaxanes containing pillar[5]arene as a macrocycle, which we functionalized by grafting mesogens and dendromesogens on the axle via Cu(I)-catalyzed alkyne-azide cycloaddition (CuAAC).
In the second place, we decided to prepare liquide-crystalline [2]rotaxanes containing two different mesogens (precursors of smectic and nematic phases) by functionalizing both the axle and the macrocycle. We first synthesized [2]rotaxanes carrying 10 azide groups on the macrocycle and 4 protected alkyne functions on the axle. The double functionalization of this scaffold, on the axle and on the macrocycle, using different mesogens is crucial to obtain a novel class of liquide-crystalline [2]rotaxanes. The aim was to explore the influence of each mesogen on the formation of mesophases and to obtain liquid-crystalline [2]rotaxanes illustrating, within the same sequence, both smectic and nematic mesophases.
Finally, the ultimate goal (by associating bulky isotropic elements and liquid crystals) is to amplify the movements of the molecular assemblies formed and to be able to possibly control the organization by movement.

Membres du jury:
Deschenaux, Robert, directeur de thèse, Université de Neuchâtel
Therrien, Bruno, Université de Neuchâtel
Nierengarten, Jean-François, Université de Strasbourg

Soutenue le 25 mars 2020

No de thèse : 2817