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Issue 5, 2011
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Temperature dependent single molecule rotational dynamics in PMA

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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 not in general reflect the instantaneous spread of local viscous properties.

Graphical abstract: Temperature dependent single molecule rotational dynamics in PMA

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Article information

28 Sep 2010
25 Nov 2010
First published
23 Dec 2010

Phys. Chem. Chem. Phys., 2011,13, 1849-1856
Article type

Temperature dependent single molecule rotational dynamics in PMA

S. Adhikari, M. Selmke and F. Cichos, Phys. Chem. Chem. Phys., 2011, 13, 1849
DOI: 10.1039/C0CP01959C

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