Étude de nouveaux polymères photoactifs à base de la coumarine du nanogel aux nanoparticules

Abstract

Coumarin and its derivates are one type of photoreactive chromophores which can undergo reversible dimerization and cleavage reactions at different wavelengths of light. By incorporating coumarin moieties into polymers and block copolymers (BCPs), the resulting materials become photoresponsive. They have attracted much attention due to their potential applications as shape-memory materials, photo-sensitizers for solar cells and drug delivery carriers. The research work presented in this thesis aimed at developing novel coumarin-containing polymers and BCPs, and investigating their potential applications as polymeric nanoparticles and films. To achieve this goal, we have designed, synthesized and characterized a number of such photoresponsive polymers and BCPs. We have studied their properties in solution and solid state in the form of several photocontrollable materials such as micelles, vesicles, nanogels, microgels, films and single chain nanoparticles (SCNPs). In the first project, we demonstrated a general strategy to prepare photoresponsive nanogels by combining the self-assembly of double-hydrophilic BCPs (DHBCPs) and the photoreaction of coumarin. These water-soluble DHBCPs have a thermo-responsive block that has a lower critical solution temperature (LCST) and is functionalized with coumarin. In aqueous solution, when the temperature is raised to above the LCST, the DHBCP forms micelles that can be cross-linked through the photodimerization of coumarin groups at [lambda]>310 nm. Upon subsequent cooling of the solution to T310 nm. Our studies have attributed this phenomenon to an imbalanced surface stress arising from anisotropic dimerization of coumarin groups. As one side of the film is exposed to UV light, the photoreaction occurs only in a region close to the surface. Since polymer density is related to the cross-linking degree, this may create a difference in tension between the two surfaces of the film and result in the observed bending. The demonstration of large-scale photoinduced deformation of an amorphous polymer opens the way for further development of photodeformable polymers.--Résumé abrégé par UMI.