Ferroelectric, antiferroelectric and TGB phases in lactic acid derivatives

We prepared a series of rod-like mesogens with two biphenyls laterally substituted by a chlorine atom in ortho position to oxygen atoms in the molecular core, having two lactate units and chiral methylbutyl chain in the chiral part. The sequences of phases and transition temperatures were ascertained by differential scanning calorimetry measurements, polarising optical microscopy, dielectric spectroscopy and electro-optical studies. X-ray diffraction studies were performed, phases confirmed and their structural parameters established. In the studied compounds twist grain boundary (TGBA and TGBC) phases were detected in a rather wide temperature range. In addition, the antiferroelectric SmC*A phase was observed. The properties of this homologue series are compared with those established previously for analogous compounds having the same molecular core and differing only in the number of lactate units in the chiral part.