POLYSILOXANE COUPLED CROWN-ETHERS AS CARRIER IN SUPPORTED LIQUID MEMBRANES

Polysiloxanes bearing benzocrown-5 moieties have been synthesized and used as carriers for K+ and Na+ in supported liquid membranes. Althoug h their lipophilicity is so high that leaching from the membrane is co mpletely suppressed, their transport efficiency and selectivity can no longer be explained by a simple 1:1 crown:cation model. A more extens ive multi-site model was developed that also takes into account cooper ative and repulsive effects between adjacent binding sites. The transp ort properties were markedly influenced by the formation of 2:1 crown: K+ complexes. No evidence was found for repulsive interactions.