The effect of lateral 1-substitution in naphthalene-2,7-diol with CH₃, CN and Cl on mesomorphic properties is studied. DSC and X-ray diffraction, texture observation and dielectric measurements have been performed. For the non-substituted core the high-temperature B_X phase and the B₄ phase occur while in CH₃ and Cl substituted compounds the B₂ phases are found. In the CN derivatives, besides the crystalline-like phase N, the phase transition between the chiral B₂ and racemic B₂ phases is observed.

Four series of new [1]benzothieno[3,2- b][1]benzothiophene derivatives have been synthesized. In the non-chiral series a SmA phase occurs, while the chiral series exhibits a rather wide antiferroelectric SmC^A* phase just below the SmA phase. The SmA-SmC^A* phase transition has been studied using DSC and dielectric spectroscopy. In the SmC^A* phase the spontaneous quantities have been measured. The tilt angle shows a typical temperature dependence and the values of spontaneous polarization are rather moderate. The length of the helical pitch increases on increasing the length of the non-chiral alkyl chain.

New series of liquid crystals with a chiral chain containing two asymmetric carbon atoms in two lactate groups have been synthesized. Some compounds have a third asymmetric centre in an (S)-2-methylbutyl alkyl chain. All the new compounds have SmA, SmC* and hexatic phases. Two of the homologues with three chiral centres also exhibit very wide SmC_A phases and one of them a re-entrant SmC* phase. The phases are characterized by DSC, dielectric, and X-ray studies. Spontaneous polarization and tilt angle are determined for the polar phases.

A new series of chiral liquid crystalline materials having the same rigid core containing a keto group, and various numbers of (S)-lactate groups in the chiral segment, has been synthesized and studied. All the compounds contain a branched terminal alkyl chain derived from (S)-2-methylbutanol. The influence of the number of lactate units on mesogenic behaviour has been studied. All the compounds show the paraelectric SmA phase and the ferroelectric SmC* phase over rather wide temperature ranges. The antiferroelectric SmC^A* phase was observed for the compound possessing two lactate groups.

A low frequency relaxation mode 1 has been detected in ferroelectric phases of three materials. The relaxation frequency and the dielectric strength of this mode depend strongly on the sample thickness, but their temperature dependences are qualitatively different in the materials studied, reflecting the behaviour of the helicoidal structure of these materials. This mode has been attributed to a superposition of the Goldstone and thickness modes when the helicoidal structure exists and to the thickness mode only, when the helix is unwound. In addition, with one material, mode 2 has been detected at still lower frequencies, and this also exhibits a strong sample thickness dependence. It was attributed to fluctuations of the director field modified by a non-homogeneous ionic charge distribution across the sample. As both modes 1 and 2 are strongly sample thickness dependent, they do not represent bulk properties of the materials studied, but reflect the structure in real samples, which is determined by surface conditions.