The temperature dependence of the layer spacings and the average intermolecular distances were studied in smectic A, C, B and nematic phases by X-ray diffraction on non-oriented samples. Two representatives of 4-n-alkoxyphenyl 4'-n-alkoxy benzoates, furthermore their eutectic binary mixture, and ternary ferroelectric mixtures obtained by the chiral additive of (R)-(1-methylheptyl)-1,1'-4'-1 "-terphyenyl-1,4 "-dicarboxilate used in different concentrations were investigated by small and large angle measurements as well.

We present a study of the influence of new chiral additives 2 and 3 on phase transition and molecular parameters of binary mixtures of cholesteryl enantate and cholesteryl laurate. The addition of these compounds to the binary mixture of the cholesteryl enantate and cholesteryl laurate results in shift of the cholesteric smectic phase transition towards the direction of lower temperatures, about 10-12degreesC. Using X-ray diffraction on the crystalline powder of unoriented samples we have determined the molecular parameters: the thickness of smectic and cholesteric layers (d) and the value of molecular parameter average distance between the long axes of neighboring molecules (D). The calculation of the value of molecular parameters d and D, indicates decrease of the thickness and packing density of the molecules of smectic layers, in Mix 1 and Mix 2, compared to 50-50% mixture.

Novel binary, ternary and four component mixtures of (S)-4-(2-chloro-3-methylbutanoyloxy)phenyl-4-[(n-alkoxy)benzoates] and 4-n-alkoxyphenyl 4-n-alkoxybenzoates were prepared exhibiting SmC* phase in a wide range near to room temperature. Phase diagrams and physical properties e.g. electro-optical response, spontaneous polarization and switching time have been determined. The appearance and disappearance of different mesophases has been studied.

Four new chiral homologous series of ferroelectric liquid crystals S-(-)-4-(2-n-alkoxy-propionyloxy)biphenyl-4'-n-alkoxy-3,5-dimethylbenzoate (DMn/m series) having O-substituted S-(-)-lactic acid as terminal group were synthesized, and characterized. They showed monotropic chiral smectic C and chiral nematic mesophases, and two representatives exhibited blue phase as well. Binary mixtures of these compounds were investigated. The effect of the lateral methyl substitutents and the length of the terminal groups on the chiral and non-chiral parts were investigated.

We present the results of study of binary mixtures of 4'-n-heptyloxyphenyl-4-n-octyloxy benzoate and 4'-(2-methylbutyl)phenyl 4-(n-heptylbiphenyl)carboxylate and 4'-n-pentylphenyl-4-(n-decyloxy)thiobenzoate. Phase diagrams of binary mixtures are formed on the basis of data obtained by the optical microscopy. It was established that the phase transition temperatures for binary mixtures are shifted significantly towards the direction of lower temperature ranges by 6-20 degrees C with respect to initial components. The mixtures exhibit nematic, smectic A, C, and B phases in a broader temperature range than that of the individual compounds. We have identified the presence of enantiotropic smectic G phase dose to room temperature. X-ray diffraction data on nonoriented samples have enabled the characterization of the structure and calculation of the molecular parameters: the layer spacings (d) and the average intermolecular distances (D) in nematic, smectic A, C, B, and G phases.

We present the results of the study of binary and multicomponents mixtures of cholesteryl oleyl carbonate with cholesteryl nonanoate, benzoate and cholesteryl chloride. The study was undertaken with the aim of forming the system with the temperature of the phase transition close to the room temperature, which could be suitable for the detection of the ionizing radiation. The phase diagrams were established on the basis of data from the optical microscopy and DS calorimetry. The mixtures wee exposed to the action of the continual spectrum of x-radiation in the period of 30/60 min. and a shift of the temperature of the phase transition towards lower temperatures in the range of 3-5 degrees C was noticed. The mixture reacts by a change of the color of the mesophase, and according to up-to-date following the results, the duration of the effects exceeds six months. Using x-ray diffraction on the crystalline powder of unoriented samples, we have determined the molecular parameters: the thickness the cholesteric layers and the average distance between the long axes of neighboring molecules.

Chiral ester derivatives of terephthalic acid containing one, three, or five phenyl rings were prepared by using (S)-2-methylbutanol or (R)-2-chloropropanol as starting materials. The one-ring terephthalates did not exhibit any liquid crystalline phases, but one of them was used as a chiral dopant in ferroelectric mixtures. Elongation of the aromatic core structure to three and five phenyl rings stabilized the SmA phase, whereas a (monotropic) SmC* phase was detected in some three-ring and five-ring derivatives. In ferroelectric mixtures based on the terephthalates, spontaneous polarizations up to 340 nC cm2 were measured.

A method has been developed for the synthesis of 4'-n-heptylbiphenyl-4-carboxylic acid-d(12). The possibilities how to retain the deuterium labelling of the starting biphenyl-d(10) and that of labelling in new positions of the above molecule in the synthetic process were studied. This procedure offers the preparation of the labelled molecule in larger scale for neutronscattering measurements. Structures and deuterium contents of all the intermediates and the final products were checked by IR, H-1 NMR and mass spectroscopy.

Some multicomponent ferroelectric mixtures have been prepared and characterized. Novel non-chiral and chiral non- mesogenic fluorine containing ester derivatives were mixed with chiral compounds and binary mixtures exhibiting smectic C phase. The physical and electrooptical properties such as tilt angle and switching time were also measured.

The review outlines the variety of molecular structures necessary for the appearance of the liquid crystalline properties, and the characteristic properties of ferroelectric mixtures which play an ever increasing role in liquid crystalline displays.

Two binary mixtures were prepared, based on three members of the homologous series of 4-n-alkoxyphenyl esters of the 4'-n-alkoxybenzoic acids. Three structurally different chiral compounds were used to make novel ternary and four-component mixtures with chiral smectic C phase. The phase diagrams of two-component, the ternary and four-component mixtures are presented and the corresponding physical and electro-optical properties such as spontaneous polarization, tilt angle and switching time are discussed. Spontaneous polarization values up to 200 nC/cm(2) were found and two distinct modes of electro-optical switching, associated with different stages of helix distortion, were observed.

A synthetic pathway is described for the preparation of the homologous series of (R)-(2-chloropropyl)-4-[4'-(n-alkoxy)benzoyloxy] benzoates with high optical purity. The liquid crystalline members of the series exhibit smectic A* phase and can be used as chiral dopants in ferroelectric mixtures. The n=8 member was used in a mixture exhibiting monotropic and the n=9 member enantiotropic smectic C* phase around room temperature.

We present the first small angle neutron scattering studies on liquid crystal polymer composite systems, where small amounts of polymers are dispersed in liquid crystals. A recent study (A. Jakli, D. R. Kim, L. C. Chien and A. Saupe, 1992, Appl. Phys. 72, 316 1) showed that even 1 wt % of polymer can induce phase separation in the form of fibres. We have found that the cross-sectional radius of such fibres is typically 300 angstrom and they have rough surfaces. The spatial distribution of the fibres does not change during the phase transitions of the liquid crystal. We have found that there is a correlation between the size of the separated polymer particles and the roughness of their surfaces: larger objects have less smooth surfaces.

The electromechanical properties of a compound exhibiting an antiferroelectric phase were investigated. An electric field induced antiferroelectric-ferroelectric transition could be detected by vibration analysis. In the antiferroelectric state the vibrations almost vanish while in the ferroelectric state the electromechanical effect has the same magnitude as in the chiral smectic C* phase.

The synthesis of 4-(2'-methylbutyl)phenyl 4'n-heptylbiphenyl-4-carboxylate-d18 (7BEF5-d18) is presented. The compound is intended to be,used as a means of studying the collective modes of liquid crystals by the coherent inelastic neutron scattering technique. The 4'-n-heptylbiphenyl-4-carboxylic acid-d12, a liquid crystalline intermediate was prepared as well; its acid chloride was coupled with 4-(2'-methylbutyl)phenol-d, to obtain the final product. The intermediates and final products were investigated by spectroscopic methods.

Copolymers have been synthesized in which chiral monomer units are combined with those of a tilted smectic homopolymer. Copolymers with the proportion of chiral units not exceeding 37% form a SF∗ phase and have therefore ferroelectric properties.

Temperature dependences of pyroelectric coefficient, spontaneous polarization and relaxation time have been measured for a series of ferroelectric liquid crystalline copolymers.

Copolymers have been synthesized in which chiral monomer units are combined with those of a tilted smectic homopolymer. The copolymers with the proportion of chiral units not exceeding 37% form a S(F)* phase and have therefore ferroelectric properties. Temperature dependences of the pyroelectric coefficient, spontaneous polarization and relaxation time have been measured for a series of ferroelectric LC copolymers.

Abstract A linear electromechanical effect was detected in a ferroelectric side chain polymeric liquid crystal. Experimental data on temperature and frequency dependence are presented.

The form of the biaxial dielectric tensor of smectics C is discussed. An experimental method and preliminary data on the tensor elements of a smectic C compound is presented.