Removal of Anions from Aqueous Media by Means of a Thermoresponsive Calix[4]pyrrole Amphiphilic Polymer

To address the challenge of removing unwanted anions from aqueous media under extraction-free conditions we have prepared a thermoresponsive amphiphilic polymer with pendent calix[4]pyrrole (C4P) receptors. Because of its amphipathicity, this polymer self-assembles into micelles in water. These micelles contain the C4P receptors buried in a hydrophobic core. This allows uptake of various cesium anions into the micelles. Due to the thermal responsiveness of the hydrophilic block chain, the anion-bearing micelles precipitate in water upon heating. Simple filtration allows their removal from the aqueous environment, thus allowing for effective water purification. Treating the anion-trapped micelles with acidic aqueous solution leads to the competition-induced release of the bound anion and thus recycling the polymeric material.