Diffusion of diblock copolymer in periodical channels:a Monte Carlo simulation study

Abstract

In recent years, the static and the dynamical properties of polymer confined in nano-channels have become a hot topic due to its potential applications in technology, such as genome mapping, DNA controlling and sequencing, DNA separation, etc. From the viewpoint of polymer physics, the properties of polymer confined in nano-channels are affected by many factors, such as the channel size, the channel geometry, the polymer-channel interaction, etc. Consequently, many researches have been extensively performed to uncover the underlying physical mechanisms of the static and the dynamical properties of polymer confined in nano-channels. Although many conformations are forbidden as polymer is confined in channels, the static properties of polymer are found to be still complicated. For the simplest case, i.e., homo-polymer confined in homogeneous solid channels, there are several scaling regimes, in which polymer adopts different conformation modes and the extension of polymer shows different scaling relations with the channel diameter, the polymer length, the persistence length, etc. In addition, the dynamical properties of polymer, such as the diffusivity and the relaxation, have also been extensively studied. Though the properties of polymer confined in homogeneous channels have been well studied, we know little about those of polymer inside compound channels. It is found that the dynamics of polymer in compound channels is quite different from that of polymer in homogeneous channels, and compound channel could be useful for DNA separation and DNA controlled movement.In this work, the diffusion of diblock copolymer(ANABNB) in periodical channels patterned alternately by part and part with the same length lp/2 is studied by using Monte Carlo simulation. The interaction between monomer A and channel is attractive, while all other interactions are purely repulsive. Results show that the diffusion of polymer is remarkably affected by the length of block A(NA), and the diffusion constant D changes periodically with NA. Near the peaks of D, the projected length of block A along the channel is an even multiple of lp/2, and the diffusion is in consistence with that of homo-polymer in homogenous channels. While near the valleys of D, the projected length of block A is an odd multiple of lp/2, and polymer is in a state with long time trapping and rapid jumping to other trapped regions in the diffusion process. The physical mechanisms are discussed from the view of polymer-channel interaction energy landscape.