The rate memory of a polymer close to T-g as elucidated by reduced 4-D NMRecho experiments

We analyze the reorientational dynamics of a polymer close to the glass tra nsition. Via comparison of two-time and four-time correlation functions, ob tained from multidimensional nuclear magnetic resonance C-13 echo experimen ts, we are particularly sensitive to the fluctuations within the heterogene ous distribution of mobilities. From variation of the experimental paramete rs we obtain a detailed picture of the interplay between jump and diffusion dynamics, including the different types of motional heterogeneities and th e geometry of the system.