Syntheses and potentiometric properties of polyethers containing thiazole and oxazole derivatives

A series of polyethers containing the thiazole or oxazole subcyclic moiety have been synthesized. Reaction of 2-aryl-4-hydroxymethylthiazole with tetr a- and pentaethylene glycol di-p-tosylate in THF provided corresponding alp ha,omega-bis[2'-aryl-4'-methylthiazole]polyethylene glycol in good yields. Similar treatment of 2-phenyl-4-hydroxymethyloxazole 7 and 2-phenyl-5-hydro xymethyloxazole 8 with tetraethylene glycol di-p-tosylate yielded the corre sponding 1,13-bis [2'-phenyl-4'-methyloxazole]tetraethylene glycol 16 and 1 ,13-bis[2'-phenyl-5'-methyloxazole]tetraethylene glycol 17 in 69 and 43% yi elds in respectively. The potentiometric properties of PVC-based ion select ive membranes containing 66 wt% o-nitrophenyloctyl ether (NPOE) and 4 wt% p olyethers 9-17 have been examined. The membranes containing thiazole and ox azole polyether derivatives exhibited high selectivity toward silver (I) io n. It was observed that the response slopes of the electrodes to silver ion vary with the length of polyether chain linking two thiazole subcyclic moi ety. Potentiometric data suggest that the number of ether units, CH2OCH2, f or phenylthiazole derivatives be greater than 5 to result in near-Nernstian response. However, the response behaviors of the membrane electrodes based on phenyloxazole podands 16 and 17, which have different orientation, were correspondingly similar to those of the electrodes based on phenylthiazole podands 9 and 10. On the other hand, the ISEs based on thiazole polyether derivatives with different terminal substituents, e.g., phenyl 10, naphtyl 14, and thienyl 15, except that with pyridyl 12, exhibited little differenc e in their potentiometric properties.