New crown-ether-functionalized alkyl(oligothiophene)s (see Figure) have been synthesized and electropolymerized to alkali metal ion sensitive poly(alkylthiophene)s. It is shown for the first time that the redox chemistry of a conducting polymer is strongly influenced by the specific host-guest interaction, although the crown ether units are not pi-conjugated to the conducting backbone but separated by an insulating oxa-alkyl chain.