Self-assembly of Amphiphilic Bottlebrush Bock Copolymers in Solution

Bottlebrush polymers are a class of branched macromolecules that have side-chains densely-grafted on a linear backbone. Bottlebrush block copolymers can rapidly undergo self-assembly into microphase separated structures in solution. However, it remains challenging to efficiently model the side-chain degrees of freedom in multi-chain bottlebrush systems. We have recently shown how to map an explicit side-chain bottlebrush to an implicit side-chain representation; this discrete worm-like cylinder (dWLCy) model simplifies the branched molecular structure to only a few coarse-grained parameters that can be modeled much more efficiently. We refine the dWLCy model by incorporating a set of coarse-grained pair potentials, informed by a scaling theory that captures inter-bottlebrush interactions. Using this new model, we perform non-dilute Molecular Dynamics simulations of bottlebrush block copolymer solution assembly. As the solution concentration increases, we observe the transition from a disordered phase to a lamellar phase, immediately preceded by strong compositional fluctuations. We compare directly with experimental results, showing agreement between these simulation results and X-ray scattering characterization of bottlebrush block copolymer solutions.