Reversible addition/fragmentation chain-transfer polymerization is used to generate a calix[4]pyrrole methacrylate-derived copolymer. The material is found to undergo supramolecular cross-linking upon exposure to select dianionic species (e.g., pyrophosphate and terephthalate salts), altering the viscoelastic properties of the copolymer in solution and in the solid state. The copolymeric material is also used for selective differentiation of mono- and bis-anions under conditions of liquid/liquid extraction.