Silver ion‐selective extraction and transport by polystyrene derivatives with pendant ethoxycyclotriphosphazene

Styrene derivatives with pendant cyclotriphosphazenes carrying ethoxy (1) and ethylene glycol monomethyl ether groups (O(CH2CH2)nCH3:2,n= 1;3,n= 2;4,n= 3) and their (co)polymers were prepared, and the selective binding and transport toward silver picrate by these ligands were examined. The extractabilities toward alkali metal and Ag+picrates are significantly affected by the length of side arms on the phosphazene ring, and1extracted only Ag+ion with a moderate efficiency, forming a 1:11‐Ag+complex. Although all of the homopolymers prepared by radical polymerization extracted almost entirely Ag+ion from the aqueous to the dichloromethane phase, the ratio of extracted amount of Ag+ion to alkali metal ions was in the range of 2.5–30. A significant improvement of the extractability toward Ag+ion was observed for poly(1‐co‐MMA) with 38.4 mol‐% of1(copoly(7)), which extracted Ag+ion with a high efficiency (65%) but has negligibly low ability to extract alkali metal ions. Reflecting this, the competitive transport in the Ag+/Na+and Ag+/K+systems with copoly(7) through liquid membrane showed that the rate of Ag+ion was 60 and 85 times higher than those of Na+and K+ions, respectively. The role of cyclophosphazene units in the selective binding and transport of Ag+ion is discussed.