METHACRYLATE-ACRYLATE BASED POLYMERS OF LOW PLASTICIZER CONTENT FOR POTASSIUM ION-SELECTIVE MEMBRANES

Polymers prepared from of glycidyl methacrylate, methyl methacrylate a nd n-butyl acrylate were studied for their possible use as a valinomyc in-based potassium ion-selective membrane with low or no plasticiser c ontent. Four polymers were observed to be functional as potassium ion- selective membranes in the presence of valinomycin and lipophilic salt . All polymeric membranes gave Nernstian or near-Nernstian responses o ver the potassium ion concentration range of 10(-5)-10(-1) M. The pota ssium selectivity over sodium, log K-KM(pot) values, for all membranes were in the range -3.0 to -4.1 as measured by the mixed solution meth od with interfering sodium ion at 0.1 M. Interference of Na+ and other cations was also studied by the separate solution method. Terpolymers prepared from methacrylate-acrylate monomers with a high n-butyl acry late ratio, required little or no o-NPOE as plasticiser to form functi onal potassium ion-selective membranes with only a slight decrease in potassium ion selectivity. The monomer n-butyl acrylate appeared to ac t as a built-in plasticiser to lower the glass transition temperature of the polymers and allowed potassium ion-selective behaviour to occur even in the absence of plasticiser.