PURPOSE: To improve the extent of introduction of a viologen structure and film-forming properties, by reacting a specified toluenesulfonylated hydroxypropylcellulose with 4,4'-dipyridyl after, if necessary, halogenating said cellulose deriv.

CONSTITUTION: Hydroxypropylcellulose (a) having a viscosity-average MW of 10,000W500,000 and toluenesulfonyl chloride (b) of formula I are reacted to obtain toluenesulfonylated hydroxypropylcellulose (A) wherein 20W100mol% of the whole OH groups of the component (a) are bound to the toluenesulfonyl groups. After the component A is reacted, if necessary, with a halogenating agent (B) to obtain a halogenated hydroxycellulose, the reaction product is reacted with 4,4'-dipyridyl of formula II or 1-alkyl-4-(4-pyridyl)pyridinium salt of formula III (wherein R is an alkyl; Z is a halogen) (C) to obtain the title deriv. wherein a viologen structure exists in the molecule or between the molecules of the component (a) and one of the groups selected from among formulas IVWVI (wherein X and Y are each a halogen or toluenesulfonyl) is bound to 2W30mol% of the whole OH groups of the component (a) through covalent bondings.