Liquid Crystal Formation in Binary Systems. VII. Liquid Crystals Induced in N-[4-(Dimethylamino)benzylidene]-4-alkoxyaniline-4,4′-Dinitrobiphenyl and Related Systems

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Abstract
By the addition of 4,4′-dinitrobiphenyl to nonmesogenic 4-(dimethylamino)-4-alkoxy derivatives of N-benzylideneaniline, smectic liquid crystals could be induced. This dinitro compound induces liquid crystals more pronouncedly than N-(4-nitrobenzylidene)-4-nitroaniline and 4,4′-dinitroazoxybenzene do when the alkoxyl group in the donor molecule is methoxyl or ethoxyl, while it induces less pronouncedly when the alkoxyl group is propoxyl. 4,4′-Dicyanobiphenyl gives a metastable nematic liquid crystal when it is mixed with N-[4-(dimethylamino)benzylidene]-4-propoxyaniline and a metastable smectic liquid crystal with N-(4-propoxybenzylidene)-4-(dimethylamino)aniline. Moreover, liquid crystals are formed in the binary systems of N,N,N′,N′-tetramethylbenzidine with 4-nitro-4-alkoxy derivatives of N-benzylideneaniline. They are metastable but cover rather wide composition ranges. The examination of the layer spacing of the smectic A phase revealed that the induced phase is a monolayer liquid crystal.