Effect of Ring Rigidity on the Statics and Dynamics of Linear Catenanes

We used molecular dynamics simulations to investigate the statics and dynamics of poly[n]catenanes for different bending rigidities of the constituent rings. We show that stiffer rings yield catenanes with more extended and, at the same time, more flexible backbones. The softening of the backbone reflects the decreasing steric interactions of catenated rings as their shape becomes more oblate due to increased rigidity. The internal dynamics of catenanes is affected too. Going from flexible to rigid rings causes a several-fold slowing of different processes, from segmental rotations and size fluctuations to Rouse modes. Finally, by considering the statics and dynamics of crowded solutions of catenanes, we isolate another emergent property controlled by the rigidity of the rings. Specifically, we show that catenanes with rigid rings hinder each other's motion more than those with flexible rings. Thus, in equally crowded solutions, the diffusion coefficient is smaller for catenanes with stiffer rings.