Etude de la mobilité moléculaire dans les systèmes amorphes complexes : multicouches de polycarbonates de bisphénol A (PC) / polyméthacrylate de méthyle (PMMA) de l'échelle microscopique à l'échelle nanoscopique

Abstract

Ce travail est consacré à l'étude de la mobilité moléculaire de liquide formateur de verre dans trois zones de température différentes : dans le liquide froid (Tcrossover >T>Tg), autour de la transition vitreuse (T=Tg) et dans l'état vitreux (TT>Tg), around the glass transition and in the vitrous state. In the firstt temperature range, the study of the evolution of molecular mobility was carried out on a model amorphous polymer, the bisphenol polycarbonate A (PC) since the appearance of the cooperativity phenomenon for T=Tcrossover until the glass transition. This was possible by combining two techniques, the TM-DSC and DDS using the theorem of fluctuation dissipation of Callen-Welton. Around the glass transition, we studied a more complex amorphous system, multi-layered films of PC/PMMA with thicknesses varying of the microscopic scale to nanoscopic scale. This enabled the identification of the influence of some parameters on molecular mobility such as the effect of confinement, the juxtaposition of 2 polymers with different chemical structures, the nature of cooperative movements in each polymer and the influence of the interdiffusion zones on the dynamics of the chains. In the vitreous state, the study of physical ageing has been realized for each amorphous polymer constituting our multi-layered films. This phenomenon was studied first considering its dynamic aspect, following the evolution of the enthalpic loss during time by DSC, then considering its dynamic aspect, following the evolution of the dynamic glass transition by TM-DSC. The whole results show the very different behaviour from the two polymers and the huge modification of the physical ageing process in the PC layers at the nanometer scale.ROUEN-BU Sciences Madrillet (765752101) / SudocSudocFranceF