Opportunities in Bottlebrush Block Copolymers for Advanced Materials

Bottlebrush block copolymers (BBCPs) are a unique class of materials that contain a backbone with densely grafted and chemically distinct polymeric side chains. The nonlinear architecture of BBCPs provides numerous degrees of freedom in their preparation, including control over key parameters such as grafting density, side chain length, block arrangement, and overall molecular weight. This uniquely branched structure provides BBCPs with several important distinctions from their linear counterparts, including sterically induced side chain and backbone conformations, rapid and large self-assembled nanostructures, and reduced or eliminated entanglement effects (assuming sufficient grafting density and that the molecular weight of the side chains is below their respective entanglement molecular weight). These distinctions allow access to large domain sizes, very rapid assembly, and the ability to preferentially add additives and/or precursors to one domain, thereby enabling the efficient fabrication of a wide range of advanced materials and devices. BBCPs have been utilized to create finely controlled and well-ordered nanostructures for use in applications, such as photonic crystals, drug delivery systems, energy conversion, energy storage devices, and key components in surface coatings. To further deploy BBCPs as templates for the formation of precise nanostructures, having a thorough understanding of their synthesis, self-assembly, and templating is necessary. To explore and understand the self-assembly and subsequent applications of BBCPs, this review emphasizes the physics of self-assembly for BBCPs (including architectural, rheological, and thermodynamic considerations) and structure-property relationships between BBCPs and their resulting nanostructures. Lastly, we provide an overview of current research trends using BBCPs in energy storage, energy conversion, photonic, 3D printing, and drug delivery applications. We aim to provide researchers with the fundamentals of BBCP self-assembly in their use as nanostructured materials to continue their development of advanced materials.