Coarse-grained models and interactions of bottlebrush polymers*

Bottlebrush polymers are a class of highly-branched macromolecules that have potential in self-assembled photonic materials applications. Despite the advancement in experimental techniques, computational studies of bottlebrush polymer solutions and melts remain challenging due to the high computational cost involved in explicitly accounting for the presence of side chains. In this work we consider a coarse-grained molecular model of bottlebrush polymers where the side chains are modeled implicitly, with the aim of expediting simulations by accessing longer length and time scales. The key ingredients of this model are the size of a coarse-grained segment and a suitably coarse-grained interaction potential between the non-bonded segments. We start from using finer grained explicit side chain models, with data obtained from Monte Carlo and Brownian Dynamics simulations. Then we incorporate the molecular information (size, stiffness, etc.) into an implicit side chain model. Finally we develop a workflow to extract the coarse-grained interactions from potential of mean force calculations, and achieve good agreements between the fine-grained and coarse-grained models. Though developed in the context of homopolymer bottlebrushes in athermal solvents, our proposed method can be extended to other solvent conditions as well as to different monomer chemistries. We expect our implicit side chain model will prove useful for accelerating large-scale simulations of bottlebrush solutions and assembly.