Effects of ring sizes on the dynamic behaviors of [2]catenane

Abstract

A hybrid mesoscopic simulation approach combining multiple particle collision dynamics (MPCD) with molecular dynamics (MD) is employed to investigate the dynamic behaviors and conformational changes of semi-flexible [2]catenanes with varying ring sizes under steady shear flow conditions. Firstly, our study reveals an irregular linear relationship between the three-dimensional surface area of the rings and the shear rate, as evidenced by changes in the surface area of the semi-flexible [2]catenane. Through schematic observations, we find that the dynamic behaviors of [2]catenanes differ for varying ring sizes. Small rings exhibit tumbling motions, medium rings show slip-tumbling motions, while large rings undergo fold-slipping motions. Medium and large rings show shear thinning conformation changes. Secondly, we analyze the normal and diagonal angles of the two rings, demonstrating that the movements in both the shear direction and the gradient direction are complete but intermittent. Thirdly, we analyze how the relative displacement vector of the center of mass between the two rings in the [2]catenane changes over time. This analysis indication of the relative motion occurring between the two rings. We also find that within certain ranges of shear rate and ring size, the two rings of the [2]catenane twist into “8” shapes, rather than slip-tumbling and fold-slipping motions. These findings provide valuable insights for guiding the transport of catenane polymers in biological systems and for designing catenane polymeric materials for industrial applications.