NEW MATERIAL:The compound of formula I (R1 and R2 are 1W10C straight- chain alkyl provided that R1≠R2).

EXAMPLE: trans-4-Ethyl-4'-propyl-ONN-azoxybenzene.

USE: A liquid crystal composition suitable for forming a matrix-driving twisted nematic liquid crystal display.

PREPARATION: Ethyl bromide is added dropwise to magnesium in THF in nitrogen atmosphere to obtain ethylmagnesium bromide (a Grignard reagent). A THF solution of p-alkylaniline of formula II is added dropwise to the Grignard reagent under ice cooling and agitation. The resultant compound of formula III is stirred under ice cooling, and a THF solution of p-alkylnitrobenzene of formula IV is added dropwise to the compound, and the reaction mixture is separated and purified e.g. by column chromatography, etc. to obtain the objective compound of formula I .