Unforced translocation of a polymer chain through a nanopore: The solvent effect

The authors have performed the Langevin dynamics simulation to investigate the unforced polymer translocation through a narrow nanopore in an impermeable membrane. The effects of solvent quality controlled by the attraction strength lambda of the Lennard-Jones cosine potential between polymer beads and beads on two sides of the membrane on the translocation processes are extensively examined. For polymer translocation under the same solvent quality on both sides of the membrane, the two-dimensional and three-dimensional simulations confirm the scaling law of tau(trans)similar to N1+2 nu for the translocation in the good solvent, where tau(trans) is the translocation time, N is the chain length, and nu is the Flory exponent. For the three-dimensional polymer translocation under different solvent qualities on two sides of the membrane, the translocation efficiency may be notably improved. The scaling law between tau(trans) and N varies from tau(trans)similar to N1+2 nu to tau(trans)similar to N with the increase of the difference of solvent qualities, and the crossover occurs at the theta temperature point, where a scaling law of tau(trans)similar to N-1.27 is found. The simulation results here also show that the translocation time changes from a wide and asymmetric distribution with a long tail to a narrow and symmetric distribution with the increase of the difference of the solvent qualities. (C) 2007 American Institute of Physics.