Anisotropic diffusion of elongated and aligned polymer chains in a nematic solvent.
The translational diffusion constant, D, of a polymer solute in a single-domain, nematic liquid crystal solvent (5CB) is measured in directions parallel and perpendicular to the nematic director using a fluorescence two-beam, cross-correlation technique. The solute under investigation is the stiff, conjugated polymer, MEH-PPV. The ratio D parallel/D perpendicular) of diffusion constants (parallel and perpendicular to the director) is observed to be 1.9 +/- 0.3. This is surprisingly small considering that MEH-PPV is known to be both elongated and highly aligned along the liquid crystal director of 5CB. We therefore argue that the structural order parameter of the solvent governs the anisotropy of the diffusion of the solute.
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Stephan
S
Department of Chemistry and Biochemistry and the Center for Nano- and Molecular Science and Technology, University of Texas at Austin, Austin, Texas 78712, USA.
Chang
Wei-Shun
WS
Yethiraj
Arun
A
Barbara
Paul F
PF