Transport of a comb-like polymer across a nanochannel subject to a pulling force

Abstract

We investigate the dynamics of comb-like polymer translocation through a nanochannel using three-dimensional Langevin dynamics simulations based on a coarse-grained chain model. A comprehensive set of simulations are performed to examine the effects of system parameters such as the grafting density $\rho$ of the side chains, the polymer chain length, the nanochannel dimensions, and the magnitude of the pulling force on the translocation dynamics. For a given polymer chain length, keeping the backbone length is constant while varying $\rho$, we have found that the dependence of the mean translocation time $\left\langle \tau\right\rangle $ on $\rho$ is non-monotonic, with a maximum translocation time for a specific $\rho$ at which the translocation is the slowest.
The simulation results also show that $\left\langle \tau\right\rangle $ is not significantly affected by the channel width above a certain radius, while the comb-like polymer translocation is hindered by a narrower channel due to increased interactions between the chain monomers and the channel. In addition, $\left\langle \tau\right\rangle $ increases linearly with the nanochannel length.
A linear scaling relationship between the mean translocation time $\left\langle \tau\right\rangle$ and the chain length $N$ of polymer is obtained, $\left\langle \tau\right\rangle \sim N$. Similarly, the dependence of $\left\langle \tau\right\rangle$ on the backbone chain size $N_{bb}$ has a quasi-linear dependence, $\left\langle \tau\right\rangle \sim N_{bb}$. On the other hand, the translocation velocity $v$ follows a power-law relationship with the polymer chain length $N$ as $v \sim N^{-1}$. The mean translocation time also shows an inverse linear relationship with the magnitude of the pulling force $F$, $\left\langle \tau\right\rangle \sim F^{-1}$. The power-law relationships discovered in this study contribute to the fundamental understanding of the comb polymer translocation dynamics and to establishing a framework for further investigations in this field.