Dynamic behavior of active polymer chain in spatially-modulated driven field

Abstract

Active polymers exhibit very rich dynamic behaviors due to their deformable long-chain architecture. In this paper, we perform Langevin dynamics simulations to study the behavior of a single self-propelled polymer chain in a plane (two dimensions) whose activity can be tuned by external field. We consider a spatially on-off periodic field along x direction, i.e. the plane is patterned into stripes of alternating active and passive regions. The width <i>d</i> of the stripes (half period length) plays a key role in determining the kinetic behavior of a flexible polymer chain. When <i>d</i> 》 2<i>R</i><sub><i>g</i>0</sub>(<i>R</i><sub><i>g</i>0</sub> is the radius of gyration of the passive flexible chain in the random coil state), the polymer chain can stay for a long time in either the active or the passive regions and moves mainly by slow Brownian diffusion; when 2<i>R<sub>L</sub></i> < <i>d</i> < 2 <i>R</i><sub><i>g</i>0</sub> (<i>R<sub>L</sub></i> is the radius of the spiral formed by the self-propelled polymer chain), the polymer chain could stay entirely in one region but cross-regional motion happens frequently; when <i>d</i> < 2<i>R<sub>L</sub></i>, the polymer chain does not stay entirely in one region and keeps moving cross-regionally accompanied by the stretching of the parts in active regions. Along with the change of the kinetic behavior of the polymer chain as <i>d</i> varies, the long-time diffusive coefficient changes by as many as two orders of magnitude and other statistical quantities such as spatial density distribution, mean total propelling force, characteristic size and orientation all show non-monotonic variation. In addition, we find four typical processes of the cross-regional motion of a flexible chain. For a semiflexible polymer chain, the cross-regional motion is accompanied by buckling behavior and the width <i>d</i> affects greatly on the degree of buckling and the continuity of the motion. Our work suggests a new idea for tuning and controlling the dynamic behavior of active polymers and is expected to provide a reference for the design and the potential applications of chain-like active materials.