Self-Assembly of Subnanometer-Scaled Polyhedral Oligomeric Silsesquioxane (POSS) Macroions in Dilute Solution

Both positively and negatively charged polyhedral oligomeric silsesquioxane (POSS) electrolytes were observed to self‐assemble into blackberry‐type supramolecular structures in water/acetone mixed solvents, driven by the counterion‐mediated attraction. Laser light‐scattering studies reveal that the sizes of the blackberry structures increase with increasing acetone content, which suggests a charge‐regulated process. Studies on two oppositely charged POSS macroions with identical charges and similar sizes show the discrepancy between positively and negatively charged POSS macroions, which is related to counterions, ionic domains of macroions, and the water‐bridged hydrogen bonding between monomers. These POSS ions further decrease the lower size limit of macroions that can self‐assemble in polar solvents reported to date. The new phenomena were observed in the self‐assembly process of POSS macroions relative to other macroion systems. Two oppositely charged polyhedral oligomeric silsesquioxane (POSS) macroions with identical charge and similar sizes can self‐assemble into blackberry‐type supramolecular structures in dilute solution. This transition from simple macroions to assemblies can be regulated by the solvent polarity.