Methacrylate-acrylate based polymers of low plasticiser content for potassium ion-selective membranes

Polymers prepared from of glycidyl methacrylate, methyl methacrylate and n-butyl acrylate were studied for their possible use as a valinomycin-based potassium ion-selective membrane with low or no plasticiser content. 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 over the potassium ion concentration range of 10(-5)-10(-1) M. The potassium 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 method 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 acrylate ratio, required little or no o-NPOE as plasticiser to form functional potassium ion-selective membranes with only a slight decrease in potassium ion selectivity. The monomer n-butyl acrylate appeared to act 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.