Metal-desorption and selective metal-trapping properties of an organized molecular film of azacalixarene-containing copolymer with spherulite-forming ability

Abstract

The metal-trapping and metal-desorption abilities and selective metal-scavenging properties of an interfacial molecular film of a highly ordered copolymer that exhibits spherulite-forming ability in the bulk state, despite having bulky azacalixarene rings, were investigated. The synthesized copolymer contained an azacalixarene ring and a crystalline polyethylene-glycol-chain-based repeating unit. The monolayer on the water surface of this copolymer was able to collect various metal ions from the subphase and trap monovalent ions; this was not possible with other derivatives. As the metal cations were incorporated via weak interactions with the applied electric field inside the azacalixarene ring, they could be desorbed or recovered by using simple ultrasonic treatment. The valences and ionic radii of the captured cations strongly influenced the desorption behavior. In addition, characteristic selectivity was confirmed by evaluating the ability to capture metals from the subphase containing multiple metal cations. The preference for the trapping ion was strongly correlated with the difficulty of desorption from the azacalixarene ring.