Die Sedimentationsgeschwindigkeit Langkettiger Makromoleküle

Abstract

The sedimentation velocity of a long‐chain molecule is greatly increased by the hydrodynamic interaction of its constituent parts. If Kuhn's model of randomly kinked molecules is accepted, the application of a formula obtained by Burgers leads to an expression for the sedimentation velocity which is shown to account for experimental results mentioned in the literature. This hydrodynamic interaction manifests itself in a way‐which illustrates the hydrodynamic meaning of the “undurchspülte Knäuel” assumed by Kuhn and makes his assumption very acceptable. It is emphasized, however, that this interaction is much less effective in the presence of a velocity gradient. This explains the experimental fact that various substances conform to Staudinger's viscosity rule, while at the same time their sedimentation constant is dependent on molecular weight.