Compression and Stretching of Confined Linear and Ring Polymers by Applying Force.

Wenduo Chen,Dazhi Jiang,Qianqian Wei,Jiayin Liu,Xiangxin Kong,Huaiyu Chen

doi:10.3390/polym13234193

Abstract

We use Langevin dynamics to study the deformations of linear and ring polymers in different confinements by applying compression and stretching forces on their two sides. Our results show that the compression deformations are the results of an interplay among of polymer rigidity, degree of confinement, and force applied. When the applied force is beyond the threshold required for the buckling transition, the semiflexible chain under the strong confinement firstly buckles; then comes helical deformation. However, under the same force loading, the semiflexible chain under the weaker confinement exhibits buckling instability and shrinks from the folded ends/sides until it becomes three-folded structures. This happens because the strong confinement not only strongly reduces the buckling wavelength, but also increases the critical buckling force threshold. For the weakly confined polymers, in compression process, the flexible linear polymer collapses into condensed states under a small external force, whereas the ring polymer only shows slight shrinkage, due to the excluded volume interactions of two strands in the crowded states. These results are essential for understanding the deformations of the ring biomacromolecules and polymer chains in mechanical compression or driven transport.

Highlights

Polymer chains are frequently stretched by imposed external constraints, such as confinement or an external force, which are geometric and tensile constraints, respectively, [1]
Several studies have considered the compression of confined DNA in microchannels via mechanical force [18,19,20,21], electric fields [22,23], and flow fields [7,10], and the results show that the compression deformations are strongly dependent on the chain rigidity, the degree of confinement, and the external force
The high-amplitude lateral deflections are suppressed by the channel walls, and the backbone is reflected from the wall; the semiflexible chain undergoing Euler buckling has a shorter wavelength

Summary

Introduction

Polymer chains are frequently stretched by imposed external constraints, such as confinement or an external force, which are geometric and tensile constraints, respectively, [1]. We study linear and ring polymers with different rigidities trapped in a microchannel and undergoing compression and stretching processes under a constant external force. [37] In Section 2, we introduce Langevin dynamics and coarse-grained models in which linear and ring polymers are compressed and stretched by a couple of external forces in a tube channel. The total energy Utotal includes the excluded-volume interactions ULJ, the bonding energy Ub, the bending potential Uθ, the repulsive interactions from the wall of the nanochannel Uwall, and the extension energy from external force Uf. The simulation details are as follows: The linear or ring polymer is modeled as a generic semiflexible bead-spring chain with N beads of mass M (M = 1.0). We runs 5 parallel samples to carry out statistical analysis

Semiflexible Polymers in Strong Confinement

Flexible Polymers in Weak Confinement

Conclusions