In this study, we unexpectedly found that sumanene (Figure , bottom) as a pristine buckybowl, enabled the formation of a buckybowl-stacked supramolecular polymer. Sumanene and its derivatives are known to form columnar structures, a type of supramolecular polymer, when in the crystalline state. More importantly, the deeper bowl depth of sumanene (1.11 Å), leading to the sufficiently slower bowl-to-bowl inversion at room temperature in the solution, is believed to be a critical factor in spontaneous supramolecular polymerization. Herein, we report the unprecedented supramolecular polymerization of pristine buckybowl sumanene. This finding prompted us to examine how external stimuli, such as temperature, pressure, and solvents, affect the supramolecular polymerization behavior. A saturated MCH solution of sumanene (1.95 mM) was dropped onto a highly oriented pyrolytic graphite (HOPG) substrate and observed using atomic force microscopy (AFM). Surprisingly, a bundle-morphological supramolecular polymer was observed (Figure ) with a 74.0 ± 28.6 nm width and a 2.7 ± 1.6 nm height, respectively (all data are given in Figure in SI). The diameter of a single sumanene molecule was calculated to be 8.2 Å, based on the X-ray crystal structure, indicating that multiple columns in a single bundle were deposited on the HOPG substrate. The change in morphology caused by changing the concentration was then investigated. When a diluted 95.3 M MCH solution was dropped onto the HOPG substrate, the bundled supramolecular polymers that were previously observed in the saturated solution were no longer present, and only globule aggregates were observed (Figure ). Therefore, the morphology can be changed by adjusting the solution concentration. To further investigate the change in morphology by changing the solvent, a 2.08 mM solution of CH2Cl2 was dropped onto the HOPG substrate; although the concentration was almost the same as that of the MCH solution, only globule aggregates were observed (Figure ). In contrast, a saturated CH2Cl2 solution of 34.3 mM, again yielded bundle-like supramolecular polymers (Figure ). These findings can be attributed to the fact that the morphology (polymer vs. aggregate) of sumanene is dynamically controlled by the concentration and solvent choice. Solvent effects are critical factors governing the states of sumanene polymers (vide infra), hence, for the first time, buckybowl-based supramolecular polymers were observed using AFM. Next, we investigated the solution-state behavior of sumanene supramolecular polymers. As shown in Figure , concentration-dependent UV spectra of MCH solutions of sumanene (4.1 M to 2.09 mM) were measured. They demonstrated that the extinction coefficients in the 0-0 band at 356 nm decreased with increasing concentration. The degree of polymerization (agg; see S9-10 in the SI) vs. Ct plot, i.e., the sigmoidal curve, indicates the formation of sumanene supramolecular polymer in MCH by the isodesmic model; its equilibrium constant (K) was calculated to be 18600 M -1 (Figure ). For example, in the case of the cooperative model, the conformations, electronic states and dipole moments in each monomer steadily change during the growth stage upon polymerization. However, as shown in Figure , density functional theory (DFT) calculations revealed almost no change in the dipole moments in each monomer unit (from monomer to heptamer), clearly indicating that sumanene polymerization by the isodesmic model is the most appropriate model (see the comparison of isodesmic vs. cooperative model in Figure and Table ). The number-average degree of polymerization (DP; see S9-10 in SI) can be calculated from the equilibrium constant; the DP at 2.09 mM was 6.7 mer.