Transport of alkali metal ions by comb-like poly(vinyl ethers) with pendant poly(oxyethylene) chains

Abstract

Comb-like poly(oxyethylenes) (\(\underset{\raise0.3em\hbox{$\smash{\scriptscriptstyle\thicksim}$}}{2} \)), prepared by the HI/I2-initiated living cationic polymerization of vinyl ethers carrying a poly(oxyethylene) pendant, were found to transport alkali metal ions (Li+, Na+, K+, and Cs+) through a dichloromethane liquid membrane at 25°C. Polymer\(\underset{\raise0.3em\hbox{$\smash{\scriptscriptstyle\thicksim}$}}{2} \) with four oxyethylene units per pendant (n = 4) transported all the four cations (best for K+), and more effective as an ion carrier than its non-polymeric counterpart (tetraglyme), whereas\(\underset{\raise0.3em\hbox{$\smash{\scriptscriptstyle\thicksim}$}}{2} \) with n = 0 [poly(ethyl vinyl ether)] was virtually ineffective. The observed polymeric effect indicates an enhancement of ion transport via a cooperative action of the neighboring poly(oxyethylene) pendants. Related vinyl ether copolymers consisting of poly(oxyethylene) (n = 4) and hydrophobic phenoxyl pendants were inferior to\(\underset{\raise0.3em\hbox{$\smash{\scriptscriptstyle\thicksim}$}}{2} \) as ion-transport carriers, but introduction of hydrophilic alcoholic pendants into\(\underset{\raise0.3em\hbox{$\smash{\scriptscriptstyle\thicksim}$}}{2} \) (n = 4) facilitated the transport of the smaller cations (Li+ and Na+).