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| Home > Publications database > Thermophoresis of a colloidal rod: Steric and electrostatic contributions |
| Home > Publications database > Thermophoresis of a colloidal rod: Steric and electrostatic contributions |
| Conference Presentation (After Call) | FZJ-2014-03832 |
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2014
Abstract: We studied the thermal diffusion behavior of dilute solutions of rod-like, charged colloids (fd-virusparticles) and fd-virus grafted by PEO (polyethylene oxide, Mw = 5000 g/mol) usinga holographic grating technique Thermal Diffusion Forced Rayleigh Scattering (TDFRS). Thesteric and electrostatic contributions have been investigated as a function of the ionic strength,which corresponds to different Debye length. In the short Debye length regime we found aclear contribution from the polymer chain, which fades out in the longer Debye length regime,where the polymer chains fit into the electric double layer. Furthermore for the non-grafted fd-viruseswe found their Soret coefficient increases monotonically with increasing Debye length,while there is a relatively weak dependence on the rod-concentration when the ionic strengthis kept constant. An existing theory for thermal diffusion of charged spheres is extended todescribe the thermal diffusion of long and thin charged rods, leading to an expression for theSoret coefficient in terms of the Debye length, the rod-core dimensions, and the surface chargedensity. The thermal diffusion coefficient of a charged colloidal rod is shown to be accuratelyrepresented, for arbitrary Debye lengths, by a superposition of spherical beads with the samediameter of the rod and the same surface charge.
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