Ni(II)-Based Metallo-Supramolecular Polymers

Abstract

This chapter introduces synthesis, ionic conductivity, and a sensor application of Ni(II)-based metallo-supramolecular polymer. Section 8.1 shows synthesis of Ni(II)-based metallo-supramolecular polymers (polyNiL12-15) by the 1:1 complexation of Ni(II) ions with bis(phenanthroline)s (L12-15). Section 8.2 describes ionic conductivity in polyNiL12-14 and the effect of the ligand modification. The introduction of hydrophobic units to the ligand markedly decreased the ionic conductivity of the polymer, probably because the formation of ion channels in the polymer film at high humidity was partially prevented by the bulky hydrophobic moieties. The electrical conductivity of the polymers is very low: only a negligible current was detected by applying a voltage up to 6 V under vacuum-dried conditions. The ionic conductivity of the polymers depended strongly on the humidity. The activation energy (E_a) is determined on the basis of the ionic conductivity measured at different temperatures at 98 %RH. E_a is calculated from the slope of the Arrhenius plot. Sections 8.3 and 8.4 show exchange of counter anion in the polymers (polyNiL14-X, X: counter anion) and the effect of the counter anion on ionic conductivity of the polymers, respectively. Section 8.5 exhibits a real-time humidity sensor application by utilizing the humidity-dependent ionic conductivity of polyNiL14-Cl.