Kinetic Control in the Self-Assembly of Rigid Sphere-Rod Amphiphiles

This study explores the kinetics regulating the self-assembly of a series of rigid, T-shaped sphere-rod amphiphiles, which contain hydrophilic Keggin clusters and hydrophobic oligodihexylfluorene rigid rods (KTOF) with tunable lengths of 2 to 6 repeating units, i.e., KTOF2 to KTOF6. Their self-assembly is triggered by the dropwise addition of poor solvent into their good solvent solutions, leading to the formation of vesicles, onion-like structures, and incomplete onion-like structures, respectively. The water titration speed is found to be directly correlated with the final assembly size, and this dependence is more pronounced for hybrids with shorter rods. To further investigate the size dependence of the assemblies, the changes in turbidity during the self-assembly process were monitored over time and fitted to the Avrami equation, revealing distinct self-assembly kinetics for hybrids with different rod lengths: amphiphiles with longer rigid hydrophobic rods grow via unimer insertion, whereas those with shorter rods exhibit dual growth modes, including unimer insertion and vesicle fusion.