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CPP: Fachverband Chemische Physik und Polymerphysik

CPP 22: Poster: Glass Transition and Dynamics of Liquids

CPP 22.2: Poster

Dienstag, 15. März 2011, 18:00–20:00, P2

Low-Temperature Dynamics in Amorphous Polymers and Low-Molecular-Weight Glasses — Study with Single-Molecule Spectroscopy — Ivan Yu. Eremchev¹, Yury G. Vainer¹, Andrei V. Naumov¹, and •Lothar Kador² — ¹Molecular Spectroscopy Department, Institute for Spectroscopy, Russian Academy of Sciences, Troitsk, Moscow reg., 142190, Russia — ²University of Bayreuth, Institute of Physics and Bayreuther Institut für Makromolekülforschung (BIMF), 95440 Bayreuth, Germany

The dynamics in several low-molecular-weight glasses and in amorphous polyisobutylene of different molecular weights is investigated with single-molecule spectroscopy at temperatures of 4.5 and 7 K. Surprisingly, only the polymers with long chain lengths follow the prediction of the standard tunneling model and feature spectral jumps of the single-molecule lines between a small number of well-defined frequency positions corresponding to the coupling to few isolated tunneling systems. Glasses consisting of smaller molecules and oligomers show much richer dynamics: In most of them the spectral diffusion is so fast that single-molecule spectra can hardly or not at all be recorded and only irregular fluorescence flares are detected. Hence, the low-temperature dynamics of disordered solids is not universal but depends on the structure and chemical composition of the material. In polyisobutylene, the transition from small-molecule-like to polymer-like behavior occurs at chain lengths of a few hundred repeat units.