Polymer translocation induced by a bad solvent.

We study polymer translocation through a nanopore subject to conformational differences created by putting two different solvents at the cis and trans compartments using Langevin dynamics in three dimensions (3D). Initially a fraction of the chain is placed in a good solvent at the cis side and the rest of the chain at the trans side is immersed in a bad solvent where it forms a globule. We study several aspects of the translocating chain as a function of the strength of the interaction ɛ/k(B)T for the bad solvent, where the temperature T is kept below the Θ temperature for the specific bead-spring model that we have used to describe the chain. For ɛ/k(B)T≥1 we find the mean first passage time (τ)~(ɛ/k(B)T)(-1) and (τ)~N(1.1±0.05). In that regard, translocation under solvent asymmetry is similar to the case of driven translocation under a bias inside the pore. However, the globule formed at the trans in the immediate vicinity of the pore readily absorbs the incoming particles making the translocation process faster than the driven translocation. Our simulation results for long chains and ɛ/k(B)T≥1 agree well with a theoretical prediction by Muthukumar [M. Muthukumar, J. Chem. Phys. 111, 10371 (1999).].