Induced re-entrant SmA phase in binary mixtures of lactic acid derivatives

Abstract

Re-entrance phenomenon is a unique effect, which is rare even in the field of liquid crystals. We synthesized a homologue series of lactic acid derivatives nZBBL, with one homologue showing a re-entrant smectic A (SmA_RE) phase at lower temperatures than the ferroelectric smectic C (SmC*) phase. However, neighbouring homologues revealed a regular mesomorphic behaviour, with only the SmA phase or with the regular SmA-SmC* phase sequence. In the presented contribution, we have prepared and pursued the binary mixtures with the aim to elucidate the re-entrance phenomenon for this molecular system. Results of our studies demonstrate how the re-entrant SmA_RE phase can be stabilized with respect to the concentration of individual homologues. Dielectric spectroscopy, X-ray diffraction studies and spontaneous polarization measurements were carried out to characterize binary mixtures and establish the phase diagrams. We found out the re-entrant SmA_RE phase in binary mixtures of homologues even though neither of them showed a re-entrant behaviour. The gained knowledge about the studied binary systems allowed us to tune the mesogenic properties in a predictable way.