Morphological Transitions in the Self‐Assembly of Rigid Sphere–Rod Amphiphiles Achieved by Adjusting the Linker Length

ABSTRACT The morphological transitions of self‐assembled supramolecular structures formed by rigid sphere–rod amphiphiles composed of hydrophilic Keggin clusters and hydrophobic oligodialkylfluorene (OF) rods were investigated by varying the alkyl linker length between the two rigid domains. For T‐shaped molecules with short C3 linkers, self‐assembly in THF/water mixed solvents always resulted in spherical onion‐like structures with a fixed interlayer distance. As the water content increases, the number of concentric layers decreases, leading to smaller onion‐like assemblies. However, with longer C15 linkers, the self‐assembly becomes more complex: they form spherical, multilayered lamellar (striped) structures in mixed solvents with lower THF content, while increasing THF content induces transitions from striped spherical structures to incomplete onion‐like structures and eventually complete onion‐like structures. UV–vis spectroscopy and analytical ultracentrifugation (AUC) confirm that C15‐linked hybrids can undergo conformational changes between T‐shaped and I‐shaped conformations in response to solvent conditions. This conformational flexibility enables K‐C15‐TOF4 molecules to adopt an I‐shaped conformation at low THF vol%, forming striped spherical structures, whereas at higher THF vol% they switch to a T‐shaped conformation, resulting in complete onion‐like structures. This study demonstrates that modifying linker length is a simple and effective strategy for regulating the morphology of self‐assembled rigid sphere–rod amphiphiles.