Rotational and translational diffusion of fluorocarbon tracer spheres in semidilute xanthan solutions

The rotational and translational diffusion and sedimentation of colloidal tracer spheres in semidilute solutions of the nonadsorbing semiflexible polymer xanthan was studied. It was found that the tracers were optically anisotropic, permitting depolarized dynamic light scattering measurements without interference from the polymer background. It was also found that the xanthan solutions behaved rheologically like model semidilute polymeric solutions with long lived entanglements. The translational diffusion was also found to be faster than predicted by the effective medium theory due to the locally inhomogeneous environment of the tracers arising from segment depletion