Electrostatic interactions between amidinium and carboxylates were used for the construction of interdigitated architectures at the air-solution interface. Spreading the water- insoluble amphiphile p-pentadecylbenzoic acid (A) on an aqueous solution of p- methylbenzamidinium (B) ions results in an intercalation of the water-soluble base between the acidic headgroups of the water-insoluble amphiphile to form an amorphous ABAB ...