NOVELTY - Ferulic acid derivative (I) is new.    USE - As liquid crystal material for liquid crystals, and for detecting element for detecting cations chosen from alkali metal ions, alkaline earth metal ions, and transition metal ions, anion detecting elements, ion conducting materials, and electrolytes (all claimed), and as electrolyte in ordinary primary cells, and secondary cells used for electric cars, note-size personal computers and portable telephones.    ADVANTAGE - The ferulic acid derivative has a long chain ethylene oxide group, which is suitable for recognition and transportation of ion, and hence used as liquid crystal material. The long chain ethylene oxide group contained in the ferulic acid derivative allows efficient transportation of the ions in 2-dimensional state of molecular aggregation. The ferulic acid derivative is economically obtained from the large amount of waste oil of rice bran, and hence promotes the decrease of the industrial waste and the development of inexpensive commercial products. Hence the derivative has high industrial utility.    DETAILED DESCRIPTION - A ferulic acid derivative of formula (I) is new:    R = polyethylene glycol, crown ether, or azacrown ether.    INDEPENDENT CLAIMS are also included for:    (1) a liquid crystal of formula (I);    (2) a liquid crystal having at least one member selected from alkali metal ions, alkaline earth metal ions and transition metal ions coordinated with a ferulic acid derivative of formula (I);    (3) detecting element of formula (I) for detecting a cation species selected from alkali metal ions, alkaline earth metal ions and transition metal ions;    (4) anion detecting element having at least one of alkali metal ions, alkaline earth metal ions and transition metal ions coordinated with (I);    (5) ion conducting material having at least one of alkali metal ions, alkaline earth metal ions and transition metal ions coordinated with (I); and    (6) an electrolyte having at least one of alkali metal ions, alkaline earth metal ions and transition metal ions coordinated with (I).