Titre de la dissertation: Designing Azo-functionalized Peptoids based on Phenylazothiazole for Solar Thermal Energy Storage: a Journey toward Eternal Sunshine.

Promoteurs: Monsieur Gerbaux et Monsieur Jérôme Cornil

Résumé de la dissertation: Renewable energies are increasingly recognized as the most promising alternatives to fossil fuels, offering clean and sustainable power sources. Among them, solar energy stands out as the most abundant: in just six hours, the Sun delivers more energy to Earth than humanity consumes in an entire year. However, its intermittent nature necessitates efficient storage and controlled release systems to enable large-scale applications.One strategy relies on molecular systems capable of light-induced isomerization into metastable states, thereby storing energy for later release. These are known as MOlecular Solar Thermal systems (MOST). When energy is needed, the photoisomer reverts to its stable form through catalytic or thermal activation, releasing the stored energy as heat.Among various photoswitching systems, azobenzene (AB) derivatives, undergoing reversible E à Z photoisomerization, are among the most extensively studied. Efforts have focused on improving key properties such as storage enthalpy, Z-isomer half-life, and absorption characteristics. To address these limitations, two strategies were explored in this thesis: (i) substituting one phenyl group with a thiazolyl moiety to red-shift absorption into the visible region, and (ii) grafting AB residues onto specific positions of a peptoid backbone to enhance energy storage capacity and prolong Z-isomer lifetime through cooperative effects.This work investigates the design, synthesis, and evaluation of phenylazothiazole (PAT) derivatives and their incorporation into peptoid backbones as novel MOST candidates. The first part focuses on the synthesis and structural characterization of various PAT derivatives, alongside evaluation of their MOST properties to assess substitution effects. The second part examines peptoid trimers incorporating PAT units, comparing their MOST performance with free PATs to determine the influence of the peptoid scaffold.Spectroscopic studies showed that PAT derivatives, whether free or peptoid-grafted, exhibit similar absorption profiles in or near the visible region—well-suited for solar applications. Notably, incorporation into peptoid backbones significantly enhances Z-isomer stability, with intermolecular interactions extending the half-life. Additional investigations into solvent effects and catalytic activation revealed a strong dependence of Z-isomer stability on solvent polarity and proticity.Overall, this thesis highlights the potential of PAT-grafted peptoids as innovative MOST systems capable of visible-light absorption without compromising Z-isomer stability. Furthermore, their properties can be finely tuned through molecular substitution. The methodology developed herein provides a robust foundation for future studies on broader families of isomers, paving the way toward next-generation MOST materials.