Abstract
Liquid crystalline 2-n-hexyloxy-5-(4-bromophenyl)pyrazine was investigated as a novel neutral ionophore for use in ion selective electrodes. Two membrane compositions were studied. The first membrane included o-nitrophenyl octyl ether as a plasticising solvent mediator, and in the second membrane the plasticising mediator was replaced with a commercial non-ionophoric liquid crystal material (E7 Merck). The inclusion of E7, which exhibits solvent mediator properties, ensured the ionophore was present in a room temperature liquid crystalline phase. For membranes containing the E7, improved Nernstian response was observed for ammonium ions over the same concentration range, together with improved selectivity when used as ammonium and caesium selective electrodes. This is believed to be the first calamitic liquid crystalline ionophore polymer system described and may have potential in direct manipulation of ionophores in polymer membrane electrodes, using established liquid crystal switching technology.