Synthèse et étude de [60]fullérodendrimères chiraux liquides-cristallins

Abstract

Fullerene-containing liquid crystals are interesting materials since they combine the properties of C60 (electrochemical and photophysical behavior) with the characteristics of liquid crystals (self-organization and order). In the first part, we prepared a family of bis-[60]fullerodendrimers and a series of tris-[60]fullerodendrimers containing chiral mesogens. The aim was to study the influence of C60 on the formation and structural organization of the chiral smectic C (SmC *) phase which can generate ferroelectric properties as well as to develop a synthetic strategy in order to increase the density of C60 in liquid-crystalline scaffolds. Our results demonstrate that it is possible to incorporate up to three isotropic C60 units within mesophases. In the second and third projects, we synthesized Janus bis- and tris-[60]fullerodendrimers. They are functionalized with two different chiral mesogens, one mesogen promoting lamellar organizations and one mesogen displaying the chiral nematic (N*) phase. Our objective was to study the influence of 1) each source of chirality, 2) the generation of each dendron and 3) the content of C60 on the mesomorphic properties. Our studies demonstrate that the liquid-crystalline properties can be modified and tuned by adjusting the size of dendritic frameworks. The Janus architecture of dendrimers increases the possibilities for controlling the mesomorphic properties with respect to conventional dendrimers. Finally, we developed a synthetic approach to insert three types of mesogens into tris-[60]fullerodendrimers. The final products, which bear two calamitic mesogens and one discotic mesogen, are accessible for the first time. The aim was to explore the influence of each mesogen on the formation of the mesophases and to obtain thermotropic liquid crystals based on C60 which can present, within the same sequence, lamellar, nematic and columnar mesophases.