Dresden 2009 – scientific programme

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CPP: Fachverband Chemische Physik und Polymerphysik

CPP 21: Polymer Physics II

CPP 21.7: Talk

Wednesday, March 25, 2009, 11:15–11:30, ZEU 114

Heterogeneous Dynamics of Polymer PMA close to Glass Transition Temperature — •Subhasis Adhikari, Markus Selmke, and Frank Cichos — Molecular Nano-photonics,Institute of Experimental Physics I,University of Leipzig,04103 Leipzig, Germany

In the study of glassy polymer systems there has been a long debate about the nature of heterogeneity of the material. There exist mainly two pictures of spatial and dynamic heterogeneities, where on one side the dynamical properties of change with the spatial position in the sample and on the other side with time at the same position of the sample. Recent experiments on single dye molecules in glassy glycerol suggest mainly a spatial heterogeneity, where each molecule shows a different dynamics. In this presentation we present recent results on this issue in long chain polymeric systems.We have analyzed the rotational diffusion dynamics of PDI dye molecule in high molecular weight glassy polymer PMA at both the ensemble and single molecule level close to Tg.Ensemble measurements have been done to compare with the single molecule measurement.From our single molecule measurements we obtain a broad distribution of rotational relaxation times of different individual molecules at a given temperature which indicates that the dynamics in some regions is orders of magnitude faster than the dynamics in other regions only a few nanometres away.Again this distribution becomes broader when temperature decreases to Tg.The rotationalcorrelation function of a single molecule is however well fitted by a stretched exponential decay. This nonexponential behavior gives a clear evidence of existence of dynamical heterogeneity.