Molecular Simulations of Poly[<i>n</i>]catenane Dynamics and Rheology

With the recent synthesis of poly[n]catenanes – polymers composed of interlocking ring molecules – the possibility of incorporating catenated moieties into functional materials continues to grow. However, catenated polymers have been only sparsely studied, as previous investigations have primarily focused on statistical, topological, or structural features, rather than the dynamics. To characterize these new systems, we conducted molecular dynamics simulations of model poly[n]catenanes in the melt. We observe unusual monomer diffusion and present a Rouse-like model that can qualitatively explain the results. We show that this model fails to account for topological interactions and that various measures of friction in the system are not self-consistent. We examine the stress relaxation and find that the viscosity exhibits a surprising non-monotonic dependence on ring size. We briefly outline how these results may be applied to material design and synthesis.