Novel approach of immobilization of calix[4]arene type ionophore in 'self-plasticized' polymeric membrane

The design of ion-selective membranes based on the immobilization of the ca lix[4]arene tetraethyl ester containing at their wider rim one polymerizabl e group in a linear isodecyl acrylate (IDA)/methyl methacrylate (MM) copoly mer is reported. Preliminary studies were focused on an optimization of pol ymeric matrix based on IDA/MM copolymers to make them suitable for preparin g ion-selective membranes. The effect of polymer composition (IDA:MM ratio) , matrix features (glass transition temperature and molecular weight) and c ompatibility with electro-active components was examined. It was found that the copolymer of IDA:MM=3:7 ratio exhibited the best mechanical properties . The feasibility of the application of IDA/MM matrix for ion-selective mem branes was examined using as a model ionophore, 4-tert-butyl calix[4]arene tetraethyl eater. Electrodes based on these membranes showed near theoretic al sensitivity towards sodium concentration and selectivity similar to repo rted for classical plasticized PVC-based membranes. Methacrylamide derivati ve of calixarene was immobilized in IDA/MM polymer of optimized composition . Potentiometric measurements revealed that the selectivity and the slope o f the response curve obtained for electrodes employing membranes with immob ilized calixarene are essentially the same as for the membranes containing a free ionophore, while the Lifetime was improved from 2 to 6 months. (C) 2 000 Elsevier Science B.V. All rights reserved.