Directly Visualizing Conformations of Bottlebrush Polymers in Bulk Films using Super-Resolution Optical Microscopy

Bottlebrush polymers have advantageous photonic and mechanical properties that are well suited for applications such as coatings, pigments, and super-soft materials. This architecture consists of a polymer backbone densely grafted by side chains, whose steric repulsions result in rigid, elongated conformations. While the single-chain conformations of these polymers have been studied experimentally for isolated chains on surfaces and within dilute solutions, few studies have probed their conformations in bulk environments. In this work, we directly visualize individual bottlebrush polymers in a bulk environment populated by other bottlebrushes, by mixing dilute quantities of fluorescently-labeled chains with unlabeled polymers and imaging through super-resolution optical microscopy (SROM). Using SROM, we resolved individual chains within thin films of bulk polymers and found the tangent correlation functions (TCFs) of the backbone. These TCFs were fit to a worm-like chain model, and values for the persistence length were extracted to quantify rigidity. Changes to these conformations were observed with variations to architectural parameters such as side chain length and grafting density.