Abstract EN:

This work is placed in the study of molecular dynamics at glass transition for polar polymers. Firstly, we have studied the characterization of few polymer serials. Secondly, we are interested to the study of molecular relaxation in the glassy state and in the glass-forming liquid state. So, we have studied three serials of materials: EVA with different content of VA, EVA hydrolyzed with different reaction time, blends of PVC/EVA. We have determined the glass transition, cristallinity and thermal degradation for each material. These results allow knowing the structure of polymers. In collaboration with chemistry laboratory UMR 6522, we correlated the material structure with the permeation properties. Indeed, these polymers used in packaging for food and good selectivities of these membranes are very interesting. Moreover, three materials (EVA containing 70% in weight of VA, PVC and a blend of these two polymers have been studied for determine the molecular dynamic at glass transition. The glass state has been characterized by Tool-Narayanaswami-Moynihan model, thus permit to understand the structural relaxation in glass. For the glass-forming liquid, we have used the Vogel-Tamman-Fulcher model and Arkhipov model. This last tries to explain all the relaxation phenomena in the glass-forming liquid. In one hand, we demonstrated that this model allow to determine the distribution of cooperative rearranging regions at glass transition in material and the a relaxation cooperativity. In regard to the fragility concept, the energy landscape is good predicted by the Random Walk Model. In another hand, we have demonstrated that the molecular dynamic is strongly correlated at the polarity of materials.