Understanding the Multiple Length Scales Describing the Structure of Bottle-brush Polymers by Monte Carlo Simulation Methods

Bottle-brush polymers contain a long flexible macromolecule as a backbone to which flexible side chains are grafted. Through the choice of the grafting density and the length of the side chains the local stiffness of this cylindrical molecular brush can be controlled, but a quantitative understanding of these phenomena is lacking. Monte Carlo simulation results are presented and discussed which address this issue, extracting mesoscopic length scales (such as the cross-sectional radius, persistence length, and contour length of these objects). Large-scale simulations of the bond fluctuation model are combined with simulations of the simple selfavoiding walk (SAW) model with flexibility controlled by a bond-angle potential, using the pruned-enriched Rosenbluth algorithm. It is shown that under good solvent conditions the bottle-brush polymers never display a pre-asymptotic Gaussian regime that would be described by the Kratky-Porod worm-like chain model, unlike the semiflexible SAW model. Implications of these results for the proper interpretation of experiments are discussed.