| Abstract: | The porous-sphere model of Debye–Brinkman–Bueche is applied to predict the limiting frictional coefficient f0 and intrinsic viscosity η] of polystyrene fractions in tetrahydrofuran and random protein coils in 6M guanidine hydrochloride. Following the formulation of Wiegel and Mijnlieff, the molecular permeability is modeled to increase exponentially as the square of the distance from the center of the molecule. A method is developed to obtain this permeability from the translational diffusion coefficient. The experimental values of f0 and η] are in satisfactory agreement with the calculated values. Also, this analysis predicts values of the Mandelkern–Flory–Scheraga parameter for flexible coils which are significantly smaller than the minimum values permitted by the Kirkwood–Riseman theory. This is in accord with the experimental evidence. |
