ABSTRACT
Polymer translocation through a nanopore has several rich molecular attributes unlike that of electrolyte ions. Whereas the transport of an ion through a channel can be envisaged as shuttling of structureless marble-like particles, the capacity of the polymer molecule to adopt many conformations and to deform under geometrical restrictions and external forces necessitates an entirely different approach. Even away from the pore, the dynamics of polymer molecules are complex. Every segment of the polymer is subjected to the Brownian forces arising from incessant collisions by the solvent molecules. As a result, each segment would have the tendency to undergo diffusion on its own right, but now modulated by the fact that the segments are correlated by chain connectivity and not independent. We may therefore expect an anomalous diffusion for a labeled monomer of the polymer. Nevertheless, for very long times and large distances compared to the polymer size, we expect the center of mass of the polymer to obey the Einsteinian dynamics. There are several characteristic timescales associated with the dynamics of the individual segments and the collective behavior of the whole chain. The description of the crossover between the behavior of polymers at short times and at long times can be cumbersome, but tremendous progress has been made for uncharged polymers (Doi and Edwards 1986).
