Dilute solution structure of bottlebrush polymers

Bottlebrush polymers are the canonical example of hyperbranched polymers,
consisting of a central backbone chain with numerous side chains densely grafted
onto it. This architecture lends additional thickness to the molecule as well
as enhancing its stiffness due to steric interaction between the side chains.
The side chain length and grafting density can be used as control parameters for tuning the material properties, as
leveraged in recent applications to photonic crystals and soft elastomers.

We present results from Brownian Dynamics and Monte Carlo
simulations on bottlebrush conformations in dilute solution, emphasizing the
role of side chain length and grafting density on the size, shape, and
intramolecular structure of a bottlebush molecule. These simualtions are based
on bead-spring models, with suitably chosen potentials.
We find good agreement between our simulation results and viscometric
studies on well-characterized samples of polynorbornene-polylactic acid
bottlebrushes. We coarse-grain the above bead-spring model as a wormlike
cylinder, where the side-chains are treated in an implicit fashion. Furthermore, we discuss the elastic response of
bottlebrush polymers to a pulling force and contextualize this behavior with
respect to classical entropy elasticity of linear polymers.