Space time observation of the -process in polymers by quasielastic neutron scattering

We report quasielastic neutron scattering experiments on the momentum ( Q ) and time ( t ) dependent dynamic structure factor on the glass-forming polymers polyisobutylene (PIB) and polybutadiene (PB). After outlining the information content of , we exemplify the concept for the case of PB. Thereafter we present data obtained on the self- and pair correlation functions of PIB encompassing a large Q range . Thereby we cover the entire motional regime from translational diffusion, the Rouse modes, the -relaxation regime up to the local relaxation processes. We investigate the limitations of the Rouse model, we present first results on the relation between the intrachain Rouse process and the -relaxation, we show that the -process may be understood in terms of backwards correlated sublinear diffusion and we finally obtain information on a local relaxation process in PIB which appears to connect a main chain relaxation with a methyl-group rotation.