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1 Opto-Electronics Review

1 2002

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Unusual behaviour of binary mixtures of ferroelectric and antiferroelectric liquid crystals with three chiral centres

Glogarova M., Novotna V., Kaspar M., Hamplova V.

Opto-Electronics Review

2002

Vol. 10, No. 1

47-52

Two binary mixtures have been studied of homologues from a series derived from 4-alkoxybiphenyl-4'-carboxylic acid with three chiral centres exhibiting ferroelectric (FE), antiferroelectric (AF) and tilted hexatic phases. One homologue exhibits a re-entrant SmC* (SmC*re) phase, which is miscible with the SmC* phase. The phase diagrams of the studied mixtures exhibit a close pocket of the SmC*A phase. The SmC*re phase is induced even in the mixtures composed of homologues without this phase. Dielectric spectroscopy reveals the Goldstone mode in both ferroelectric SmC* and the SmC*re phases, this mode being stroger when increasing concentration of the antiferroelectric homologue. In the SmC*A phase a relaxation mode is detected with the relaxation frequency three orders higher, which exhibits critical slowing down when approaching the SmC*re phase. This mode, which can be attributed to the anti - phase mode, is responsible for the apperance of SmC*re phase. In mixtures exhibiting the SmC*A phase a helix twist inversion occurs in the vinicity of the low temperature border of the AF phase.