Starting from neutral "pro-ionomeric" diblock copolymers, photoluminescent benzobis(imidazolium) (BBI) dihalide salts are used to effect anion metathesis, affording fluorescent block ionomers in a single step. In aqueous media, the ionomers self-assemble into either core- or shell-crosslinked micellular structures, depending on the copolymer and BBI used (see figure).