空间调制的驱动外场下活性聚合物的动力学行为

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

活性聚合物由于其可形变的长链构象而表现出更丰富的动力学行为.本文通过郎之万动力学模拟研究了在周期性外场调制下活性聚合物的运动行为.我们发现柔性聚合物链有4种跨区域运动模式.外场的周期性区域宽度在活性聚合物行为的调控方面起到了关键作用.比如随着区域宽度的改变活性聚合物的扩散系数可以发生高达两个数量级的改变,其余如链的统计空间密度分布、整体受力情况、特征尺寸和取向等都表现出明显的非单调变化.这些变化反映了不同区域宽度下,聚合物链的构象特征及运动模式的改变.我们的研究为设计和调控活性聚合物的动力学行为提供了新思路,有望为可形变链状或长条状活性物质在生物、医学和材料领域的潜在应用提供参考.

Active polymers exhibit very rich dynamic behaviors due to their deformable long-chain architecture.In this work,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 the x direction,i.e.the plane is patterned into stripes of alternating active region and passive region.The width d of the stripe(half period length)plays a key role in determining the kinetic behavior of a flexible polymer chain.When d>>2 Rg_(0)(Rg_(0) 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 region or the passive region and moves mainly by slow Brownian diffusion;when 2 RLg_(0)(RL is the radius of the spiral formed by the self-propelled polymer chain),the polymer chain could stay entirely in one region but crossregional motion happens frequently;when d<2 R_(L),the polymer chain does not stay entirely in one region but keeps moving cross-regionally accompanied by the stretching of the parts in active regions.With the kinetic behavior of the polymer chain changing as d varies,the long-time diffusive coefficient changes by as great 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-mono tonic variations.In addition,we find four typical processes of the cross-regional motion of a flexible chain.For a semiflexible polymer chain,the crossregional motion is accompanied by buckling behavior and the width d affects greatly 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 provides a reference for the design and the potential applications of chain-like active materials.