Observation of a transition from non-switchable B-7 mesophase to an antiferroelectric sub-phase in strongly polar bent-core compounds

The synthesis and characterization of two new homologous series of five-ring Schiff's base esters exhibiting the non-switchable B-7 mesophase are reported. These compounds have been derived from either 2-nitro- or 2-cyanoresorcinol. Interestingly, three higher homologues of the nitro-substituted compounds undergo a transition from the non-switchable B-7 mesophase to an antiferroelectric sub-phase (B-7AF1), which is the first example of such a transition. In addition to comparing the mesomorphic behaviour of the two series of compounds, the effect of reversing the azomethine linkage group in these series of compounds has also been examined. The mesophases have been characterized by conventional techniques.