MOBILITY OF A REPTATING POLYMER

The reptation model for the dynamics of an entangled polymer is considered for the case where the diffusion is driven by a weak field. If the distance between entanglements is greater than the persistence length, the mobility of long chains is predicted to be independent of their size and proportional to the field strength. This difference from previous predictions is due to the fact that fluctuations alter the field dependence of the tube orientation. Implications for the separation of DNA using gel electrophoresis are discussed.