We synthesized several polyether dicarboxylic acids with naphthalene and trimethylene groups as repeating units. The polyethers selectively formed complexes with lithium, an alkali metal. In contrast to the typical polyethers, their alkali metal complexes exhibited very low solubilities for water and hydrophobic organic solvents such as chloroform and toluene. Polyethers having seven naphthalene units formed a stable monolayer on an aqueous subphase, only when alkali metal hydroxides were added, but not acid.