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A joint analysis of the molecular geometry and crystal packings of the members of a homologous series of 4 alkyloxycyanobiphenyl C n H 2n + 1 -O-C 6 H 4 -C 6 H 4 -CN with n = 5-12 does not reveal a direct relationship between the molecular geometry and mesogenic properties of these compounds. The crystal packings of all of them are built from alternating loose aliphatic and dense aromatic regions. The closely packed aromatic regions of crystals exhibit weak intermolecular directed interactions of different natures which are responsible for the occurrence of the mesophase. The type of mesophase depends on the number s of structure forming elements, the ratio of their energies (if s > 1), and the melting temperature of the com pound. A graph system is used to describe the crystal packings and the mesophase. It is shown that, although the mesophase graph is similar to the crystal graph, they may differ somewhat, because some symmetric lim itations (for example, lattice) on the molecular associate structure are removed in the melt.

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