Macrocyclic ligands on polymers

Abstract

Abstract The ion binding properties of linear polymers carrying crown ether ligands as pendent groups are reviewed. The polymers often exhibit selective cation binding different from that of their monomeric crown analogues. One of the polymers, poly(vinylbenzo-18-crown-6), behaves in water as a neutral polysoap and strongly interacts with organic anions. The binding is enhanced and also can be regulated by charging the polymer with crown complexable cations. This polymer also catalyzes solvent sensitive reactions by a micellar type mechanism. In the decarboxylation of 6-nitrobenzisoxazole-3-carboxylate in water the substrate bound to the Cs+ charged poly(crown ether) decomposes 14000 times more rapidly than in water. In benzene the decarboxylation is also accelerated by poly(crown ethers), but in this case as a result of anion activation. Poly-(crown ethers) were also found to form polysalt complexes in water with several polyanions in the presence of crown complexable cations. In the absence of salts, complexes can be formed with polyacids through hydrogen bonding.