Xanthan translational diffusion coefficient

In a quasielastic light scattering study of macromolecular solutions, it is essential to establish a clear relationship between the experimental conditions and the type of relaxation phenomena manifest in the light scattering data. To accomplish this, one must perform experiments over a range of scattering angles and solution concentrations. One of our objectives is to determine the translational diffusion coefficient (D ) for xanthan, and to relate this parameter to a hydrodynamic size. 

The translational diffusion coefficients of the xanthans could not be measured by a dynamic light scattering technique. Other modes of motion in addition to translational diffusion may have been detected at the 40° scattering angle as a direct result of the high pol3nmer molecular weights. 

Fig. 17. Translational self-diffusion coefficients for aqueous solutions of five xanthan samples [127], Solid curves, the theoretical values calculated from Eq. (67) along with Eqs. (46) and (58)...

Koenderink, et al. examined the motion of perfluorinated hydrocarbon spheres through xanthan solutions(72). Depolarized QELSS spectra were measured at a series of angles and fitted to second-order cumulant expansions. The spheres had radius 92.5 nm the xanthan molecular weight was 4 MDa. Koenderink, et al. measured solution viscosity, shear thinning, storage and loss moduli, translational and rotational diffusion coefficients Dp and Dr of the probes, and probe sedimentation coefficient s, and made an extensive and systematic comparison... 

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