A wide range of functional materials have leveraged these unique properties in a wide range of applications; for example, the decreased conformational degrees of freedom has been used in the context of surface-adsorbed bottlebrush materials, such as molecular pressure sensors that detect film pressure at liquid solid interfaces, pressure sensitive adhesives, pH-responsive surfaces, and stimuli-responsive molecular brushes. The suppression of molecular entanglements has been used to great effect in bottlebrushes with block copolymer constituents, which undergo microphase separation to form well-ordered domains. The reduced entanglement and stretched conformation allows these domains to reach length scales appropriate for photonic and phononic crystals, that would otherwise be kinetically difficult to form with linear block copolymers. This reduced entanglement effect is also exploited in designing low modulus elastomers capable of strain-hardening and sustaining large deformation, with applications in artificial muscle development and camouflage technology via strain-adaptive structural coloration. Bottlebrush architectures are also encountered in biological systems, often in environments where they play a functional role of providing structural support and altering mechanical properties. For example, aggrecan, a proteoglycan with a bottlebrush-like structure occurring in cartilage, is partly responsible for controlling the mechanical strength of cartilage via its interaction with collagen fibres. Similarly, neurofilaments provide structural support to myelinated axons in vertebrate nerve cells via hydrogelation of the strongly interacting side chains. N sc N bb 1 / f Due to the utility of bottlebrush polymers, it is crucial to understand how to design their architecture and chemistry to yield desired material properties. This represents a challenge to both polymer chemists and polymer physicists, which has received a significant amount of interest over the past few decades. For polymer synthesis, the primary challenge has been to increase the versatility of the bottlebrush chemistry while also developing well-controlled polymerization schemes to obtain bottlebrushes with monomodal molecular weight distributions. For most chemistries, this limits the backbone degree of polymerization (DP) to ca. 1000 monomers with a sidechain DP of 100-200, however individual examples of longer backbones have been reported. For polymer physicists, the overall challenge is the sheer number of choices for tuning the macromolecular architecture and chemistries, which represents a large parameter space that makes Edisonian molecular design inefficient. For example, it is possible to have varying graft densities and backbone topologies; 41 constituent chains can be of varying flexibility or incorporate block copolymers that exhibit intramolecular phase separation. Similarly, bottlebrushes with dendritic side chains and gradients in side chain DP have also been considered.