The formation of planar ribbonlike aggregates from stiff polyanions in the presence of anisotropic cations.

A dilute salt-free solution of rodlike polyanions in the presence of anisotropic (chain) cations consisting of neutral tails and charged heads is studied. Using Monte Carlo simulation within the framework of the primitive model, different Coulomb coupling regimes were considered. While aggregation in the strong coupling limit is expected, we report new morphology, namely, the formation of ribbonlike nanostructures. At strong electrostatic interaction, the system is found to undergo the self-organization resulting in the formation of planar aggregates that look like a "ladder" of polyanions sandwiched between cationic chains. We investigate the stability of different morphologies and find that these aggregates are thermodynamically stable. Focus has been made on how the chemical structure of anisotropic cations affects the morphology of the aggregates.