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Cyclic bottlebrush polymers combine the promise of densely-grafted macromolecular architectures with the mechanical advantages of cyclic polymers for diverse applications across materials science. 

Abstract The synthesis and processing of π‐rich polymers found in novel electronics and textiles is difficult because chain stiffness leads to low solubility and high thermal transitions. The incorporation of “shape‐shifting” molecular cages into π‐rich backbone provides an ensemble of structural kinks to modulate chain architecture via a self‐contained library of valence isomers. In this work, we report the synthesis and characterization of (bullvalene‐co‐phenylene)s that feature smaller persistence lengths than a prototypical rigid rod polymer, poly(p‐phenylene). By varying the amount of bullvalene incorporation within a poly(p‐phenylene) chain (0–50 %), we can tune thermal properties and solution‐state conformation. These features are caused by stochastic bullvalene isomers within the polymer backbone that result in kinked architectures. Synthetically, bullvalene incorporation offers a facile method to decrease structural rigidity within π‐rich materials without concomitant crystallization. VT NMR experiments confirm that these materials remain dynamic in solution, offering the opportunity for future stimuli‐responsive applications.