Simulation and Analysis of Molecular Bottlebrush Dynamics in Dilute Solutions

Molecular bottlebrushes consist of a linear polymer backbone that is densely grafted with side chains. They have received considerable attention due to their unique physical properties (e.g., very high entanglement molecular weights) relative to linear homopolymers. To date, their relaxation dynamics have received significantly less attention than their conformation and self-assembly. In this article, we make use of dissipative particle dynamics (DPD) simulations with proper orthogonal decomposition (POD) to study the relaxation dynamics of bottlebrushes in dilute solutions. The modes obtained by POD suggest that the backbone behaves identically to a linear chain and that the motions of its monomers are coupled to the side chains because of their grafted state. Although simulations of linear chains behaved as expected from the Zimm model, the scaling of the relaxation times of the bottlebrushes with R-g followed an unexpected scaling relationship tau similar to R-g(3.4). Our simulations demonstrate that the origin of this scaling law resides in differences between the scaling of R-g and the hydrodynamic radius R-h as the bottlebrush molecular weight is varied and that the Zimm model accurately describes dilute solutions of bottlebrushes.