Conductance studies of salt solutions in the presence of poly(vinylbenzo crown ethers)

Abstract

AbstractThe conductance of acetone and methyl ethyl ketone solutions of tetraphenylborate salts in the presence of homopolymers and styrene copolymers of vinylbenzo‐15‐crown‐5 and vinylbenzo‐18‐crown‐6 was studied, and the results compared with data obtained for crown ethers. Polycations are formed on binding cations to the poly(crown ethers), and the conductance behavior of the polyelectrolytes depends on the nature of the cation‐crown complex and the spacing between crown moieties which in turn determines the charge density on the polymer chain. The compositions of the crown‐cation complexes were determined for crown ethers. The complex formation constants of sodium and potassium cations to poly(vinylbenzo‐18‐crown‐6) were found to change as more cations bind to the chain. This is not the case for the copolymers where the crown ligands are spaced farther apart. A mixture of poly(vinylbenzo‐15‐crown‐5) and 10−3M potassium tetraphenylborate in methyl ethyl ketone or acetone has a minimum conductance at a crown to cation ratio of 3.0, but the conductance rapidly increases on addition of crown ether. This was used to qualitatively determine the binding efficiency of a series of crown ethers since the rate of increase in the conductance is a measure of the binding ability of the crown ether to the cation.