Driven polymer translocation in good and bad solvent: effects of hydrodynamics and tension propagation

TL;DR

This study examines how hydrodynamics and solvent quality influence driven polymer translocation through nanopores, revealing distinct behaviors in good versus bad solvents and introducing a new tension propagation measurement method.

Contribution

It presents a novel method to measure tension propagation during translocation and compares hydrodynamic effects in good and bad solvents using stochastic rotation dynamics simulations.

Findings

Hydrodynamics reduces translocation time in good solvent.

Tension propagates similarly with or without hydrodynamics in good solvent.

In bad solvent, hydrodynamics speeds up collective motion but not individual monomers.

Abstract

We investigate the driven polymer translocation through a nanometer-scale pore in the presence and absence of hydrodynamics both in good and bad solvent. We present our results on tension propagating along the polymer segment on the cis-side that is measured for the first time using our method that works also in the presence of hydrodynamics. For simulations we use stochastic rotation dynamics, also called multi-particle collision dynamics. We find that in the good solvent the tension propagates very similarly whether hydrodynamics is included or not. Only the tensed segment is by a constant factor shorter in the presence of hydrodynamics. The shorter tensed segment and the hydrodynamic interactions contribute to a smaller friction for the translocating polymer when hydrodynamics is included, which shows as smaller waiting times and a smaller exponent in the scaling of the translocation time with the polymer length. In the bad solvent hydrodynamics has a minimal effect on polymer translocation in contrast to the good solvent where it speeds up translocation. We find that under bad-solvent conditions tension does not spread appreciably along the polymer. Consequently, translocation time does not scale with the polymer length. By measuring the effective friction in a setup where a polymer in free solvent is pulled by a constant force at the end, we find that hydrodynamics does speed up collective polymer motion in the bad solvent even more effectively than in the good solvent. However, hydrodynamics has a negligible effect on the motion of individual monomers within the highly correlated globular conformation on the cis-side and hence on the entire driven translocation under bad-solvent conditions.