Dresden 2011 – wissenschaftliches Programm

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CPP: Fachverband Chemische Physik und Polymerphysik

CPP 26: Polymer Dynamics

CPP 26.4: Vortrag

Mittwoch, 16. März 2011, 11:15–11:30, ZEU 160

Temperature dependent single molecule rotational dynamics in PMA — •subhasis adhikari, markus selmke, and frank cichos — Molecular Nanophotonics Group,Inst. of Expt. Phys. I, Univ. of Leipzig, 04103,Leipzig,Germany

Temperature dependent measurements of the rotational diffusion of single dye molecules in the polymer poly(methyl acrylate) (PMA) are presented and compared to shear viscosity data and numerical simulations of the rotational diffusion process. It is found that single molecule rotational diffusion very accurately follows the Debye-Stokes-Einstein predictions for the shear viscosity without any additional parameter. We employ a simple model of dynamic changes of the rotational speed of a single molecule. This dynamic heterogeneity model is based on a Gaussian distribution of activation energies in a VFTH (Vogel-Fulcher-Tammann-Hesse) type temperature dependence of the polymer viscosity. The simulations explain all experimental details concerning the stretched exponential single molecule relaxation dynamics and the related distributions. They also reveal that the observed distributions are related to the intrinsic physical properties of the polymer but do in general not reflect the instantaneous spread of local viscous properties.