Electrophilic reactions at the molecular core of (flat) 2,3,6,7,10,11-hexa(alkoxy)triphenylene lead mainly to seven fold substituted derivatives. Surprisingly, despite their overcrowded and therefore, grossly distorted structure, these products exhibit the same type of columnar mesophase as their precursors do, however, usually wider in range which may even be more stable. Semi-empirical calculations on such novel hexaethers with one or two additional and in most cases electron withdrawing substituents reveal clearly that these new molecules are twisted due to the crowding in them. Therefore, these triphenylene derivatives are potentially helical-chiral. Attempts in connection with their resolution into the first enantiomers of this kind in triphenylene chemistry are an interesting challenge and, therefore, in progress.

Novel amphotropic liquid crystals have been synthesized and their thermotropic and lyotropic phase behavior was investigated by polarizing microscopy and x-ray scattering. These compounds are biphenyl derivatives with a terminally attached hydrophilic 1,2-diol group and 4,4''- didecyloxyterphenyl derivatives with a laterally attached diol group. The diol groups are separated from the rigid cores by means of polyether chains of different length.In dependence of the length of these polyether chains smectic and columnar mesophases have been found. The columnar mesophases may be regarded as ribbon phases resulting from the collapse of a smectic layer structure into band-like segments. Columnar phases were also found in binary mixtures consisting of conventional amphiphiles and bolaamphiphiles as intermediate phases between the smectic double layer and the smectic single layer phase. We can conclude, that the formation of columnar mesophase by rod-like molecules is a more general phenomenon which occurs if strong intermolecular interactions force the molecules to arrange in layers and simultaneously the molecular architecture is not compatible with a smectic layer structure due to steric repulsion or unfavorable dipolar interactions.

Banana-shaped molecules have been prepared and their mesophase behavior was investigated. The constitution of the fiber-ring compounds was varied, e.g. with the type and direction of connecting groups and, especially, the influence of substituents situated at different positions of the angled middle part. According to preliminary investigations by x-ray measurements, polarizing microscopy and mixing behavior several mesophases could be distinguished. Ferroelectricity could be detected only for one of the phases by electro-optical switching and pyroelectrical investigation.

The chromophoric biheterocycle 2,5-dihydropyrrolo(3,4- c)pyrrole-1,4-dione as a widely variable basic core structure has been introduced into liquid crystal research. The first eight calamitic examples of such thermomesomorphic derivatives are presented and discussed here.

A number of 1-(4-substituted phenyl)-2-(4-(alken-3-yl- 1)phenyl)ethynes have been synthesized by coupling of 4- substituted phenylacetylenes with new intermediates 1-(4'- iodophenyl)-alkenes-3, which were prepared by a reaction of either allylmagnesium chloride or crotylmagnesium chloride or crotylmagnesium chloride with 4-iodobenzyl bromide. The resulting compounds form mesophases - predominantly nematic - in a wide temperature range and enhance optical birefringence of nematic materials.

The synthesis and mesomorphic properties of di- and three- ring alkanoyl substitute 5-aryl- (and trans-4-aryl- cyclohexyl)-2-alkycyclohexan-1-ones are described. The compounds were prepared starting from the corresponding 3- aryl- (or trans-4-arylcyclohexyl)-6-alkylcyclohex-2-en-1- ones which were catalytically hydrogenated into saturated trans-cyclohexanones and then acylated in the usual way using a Friedel-Crafts procedure.

3,6-disubstituted cyclohex-2-en-1-ones were used as intermediates for preparation of different mesogens with lateral substituted cyclohexane or cyclohexene ring. Starting from two different 2,5-distributed cyclohex-2-en-1- ones or two series of compounds were synthesized. Their mesogenic properties by thermomicroscopy and DSC were investigated.

4-(trans-4-alkanoylcyclohexyl)cyanobenzenes and 4-alkyl 4- (trans-4-alkanoylcyclohexyl_benzoates have been synthesized and their viscosity, optical indices, dielectric and elastic constants have been measured.

New family ofliquid crystalline compounds was synthesised. Polymorphism was detected with the help of the DSC calorimetry and polarizing microscopy. Monotropic ordered smectic mesophase for the derivatives from the pentyl up to the dodecyl was found. These phases situations are discussed and they are compared with the structure of other ferroelectric liquid crystalline compounds. Keywords: Liquid crystals, Smectics. Azo compounds. DSC calorimetry, chiral compounds.

Two families of liquid crystalline compounds: 4-hexyl-4-alkoxyazobenzenes and 4-heptyl-4'-alkoxyawbenzenes have been synthesised for alkyl chain from methoxy up to octadecyloxy. On the base of the DSC calorimetry and polarizing microscopy rich polymorphism was detected. Maximum four mesophases were found: nematic, smectic A, smectic C and smectic I. The interesting even-odd effects for temperature of clearing was observed similar to the other families of 4-alkyl4'-allcyloxyazobenzenes. The phase diagram sequence and temperatures of phase transition are discussed and there are compared their entropy effects to those of the other azobenzene liquid crystalline compounds.

A homologous series of various compounds with polar terminal groups conjugated with carbon-carbon double bonds: the cyanoethylene, cyanobutadiene, and fluorocyanoethylene groups were prepared. These derivatives have very wide mesomorphic temperature ranges. Moreover, by measuring physical properties, the mixtures containing this series were found to have large dielectric anisotropies and appropriate birefringence values. The x-ray diffraction measurement of the cyanoethylene derivatives supports an anti parallel dimer conformation in their smectic phases. A fluorine atom at the (alpha) position of the cyano group prevents the formation of such electrostatic dimers. It is concluded that the wide mesomorphic temperature range of these derivatives was caused by the stronger molecular interaction. Moreover, the derivatives which can form dimer structures showed the wider mesomorphic temperature ranges.

Six new calamitic liquid crystals incorporating 1,12- dicarbadodecahydro-closo-decaborane into the core have been synthesized. All materials exhibit nematic phases and two compounds are also smectic. Comparison with known analogues demonstrates that p-carborane can be an effective constituent of mesogens and also suggests that it suppresses smectic phase formation.

Novel mesogenic para-substituted dibenzo-18-crown-6 (I a-c) and dibenzo-24-crown-8 (II d, e) are studied. Synthesis and the structural investigations of 4,4'(5')-bis(4''- alkoxybenzylidenamino)-dibenzo-18-crown-6 (I-a), 4,5'-bis (3''-(4''-alkoxyphenyl-)-3''-oxo-1''-propenyl-amino)- dibenzo-18-crown-6(I-c), 4,5'-bis(4''-(4'''- alkoxybenzoyloxy)-benzylidenamino)-(II-e) are presented. The high temperature nematic phase is observed for the trans- isomers of materials I-b,c and II-d,e. The aroylvinylamine- derivatives (I-c, II-e) have higher phase transition temperatures than relevant azomethine derivatives (I-b, II- d). Among studied compounds the material II-d is the most stable. Materials I and II have also rather complex solid state polymorphism. The structure of Cr-8 (II-d and II-e) was investigated by the x-ray scattering method. In crystal phases of II-d and II-e the monoclinic lattices have been found with a equals 5.48 angstrom, b equals 8.34 angstrom, c equals 47.3 angstrom (beta) equals 124 degrees and a equals 45.0 angstrom, b equals 8.8 angstrom, c equals 13.8 angstrom, (gamma) equals 111 degrees parameters, respectively. The conformation of a central crown-ether fragment in the crystal as well as in nematic phase is suggested.

Several azo derivatives of benzo(1,2-d:4,5-d')bisthiazole have been prepared. Obtained dyes exhibit positive dichroism in liquid crystalline mixtures with absorption bands in range 400-600 nm.

3,4-Dialkoxybenzoates of pentaerythritol and structural related polyhydroxy compounds have been synthesized and investigated by polarizing microscopy, differential scanning calorimetry and some of them also by x-ray scattering. Despite the fact that these compounds are neither anisometric nor amphilphilic in a classical sense they can display columnar liquid-crystalline phases. It is proposed, that the segregation of the polar regions and the lipophilic alkyl chains into separate regions is mainly responsible for the formation of these mesophases.

Prediction of physical properties from the chemical structure can be done by analyzing the data contained in the database LiqCryst. The potential of the similarity concept as used by the database can be shown in the case of nematic liquid crystals: 22,013 monomeric compounds are known to show a nematic phase. The similarity concept can be applied to 19,590 of these and the difference between predicted and known transition temperatures of the substances are astonishingly small: for 11,773 the difference is less than 5 degrees C. For 17713 the transition temperature can be predicted to within +/- 15 degrees C.

To continue previous works on prediction of discotic mesomorphism (DM) new selection has been investigated for disc-like compounds based on polysubstituted cyclotriveratrylene and tetrabenzocyclophane types. The following molecular parameters have been computed: K, K_c, K₈, K_p,M_m, M_r and the mesophase appearance prediction probabilities have been estimated by specified ones. The analysis of 150 hypothetical structures was carried out and the part of them with predicted DM was chosen for further investigations.

Low-molecular liquid crystals containing silicon were synthesized. Concerning the purpose of the silicon tow aspects are of interest. Firstly, short siloxane segments are terminally attached to the mesogens which have a rod- like shape or a wedge-like one. This allows us to study the effect of opposite forces, especially of steric interaction and separation tendency, on the mesophase behavior. For the siloxan containing rod-like mesogens it can be observed that the smectic layers consist of two sublayers separating the incompatible moieties of the compounds. Secondly, the silicon is used as sp³ hybridized branching point to introduce three alkyl chains at one terminal position of the molecules.

Using gas chromatograph coupled with m ass and IR detectors, the degradation products that are compared when 4-(trans-4- pentylcyclohexyl)fluorobenzene is heated in the air at 150 degrees C were identified. It was found that in these conditions mainly the oxidation of the cyclohexane ring takes place. Among the degradation products of 4-(trans-4- pentylcyclo-hexyl)fluorobenzene there are alcohols, ketones and carboxylic acids.

New series of ferroelectric liquid crystals derived form alkoxycinnamic acid containing chiral alkyllactate group was synthesized. All compounds have a wide temperature range SmC^* phase at temperatures above 100 degrees C and high spontaneous polarization. Some of homologues exhibit spontaneous helix twist unwinding in the SmC^* phase accompanied with the helix twist inversion.

Some new liquid crystalline allene derivatives incorporating a heterocyclic 1,3,4-thiadiazole ring as a constituent of the rigid core have been synthesized both as racemats and in enantiometrically enriched forms. The compounds were investigated by polarizing microscopy and by differential scanning calorimetry. The three ring compounds exhibit broad regions of smectic C-phases. Most of the optically active compounds show broad Sc^*-phases with moderate values of the spontaneous polarization.

Two antiferroelectric liquid crystals (S) 4-(1- methylheptyloxycarbonyl)phenyl 4'-(3-butanoyloxyprop-1- oxy)biphenyl-4-carboxylate and (S) 4-(1- methylheptyloxycarbonyl)phenyl 4'-(3- perfluorobutanoyloxyprop-1-oxy)biphenyl-4-carboxylate have been prepared and their phase situation investigated by DSC, XRD and dielectric methods.

Xylose is a suitable source for chiral liquid crystal. Several compounds with different substituents were synthesized and their mesogenic properties were described. Cholesteric phases, blue phases, ferroelectric phases and TGB_A phase were observed.

The chiral effects displayed by trioxadecalin derived liquid crystals are summarized. All these mesogenic properties depend strongly on small changes in the molecular structure. It is therefore possible to obtain a wide array of different chiral effects like helix inversions, blue phases, TGB_A phase, S_C* phase to name only some of them by changing only a small part of the molecule, meanwhile the basic mesogenic core is kept constant. In addition the mesogenic properties of new trioxadecalins are described, that have been obtained by a new synthetic pathway.

The synthetic pathways of preparation of new optically active 1,1-binaphthyl (BN) derivatives containing various radicals including mesogenic ones were suggested and realized. No mesophase was found, but having atropisomeric chirality origin the novel substances proved to be effective chiral dopants inducing the highly twisted supramolecular structure both in low molecular mass and in polymer liquid crystals (LC). The helical twisting power (HTP) in two different standard nematic mixtures and in the copolymers based on the nematogenic methoxy-phenyl benzoate acrylic monomer was investigated. The systematic growth of the HTP in the low molecular mass nematics was found when the longer or mesogenic radicals were attached to the binaphthyl core. In the LC-copolymers the HTP of the BN-monomer and mesophase stability were analyzed depending on temperature and the molar fraction of the BN-fragments. The observed HTP value was found to be about thrice as much as those reported for the cholesterol and binaphthyl chiral monomers.

The smectic-A to nematic (AN) transition was studied under confinement as introduced by the randomly interconnected voids of Millipore filters. Using a high resolution calorimetry it was determined that heat capacity peaks evolve from sharp and prominent to broad and small with decreasing void size. The random confinement drives the heat capacity critical exponent from the bulk value towards zero, the 3D-XY model prediction, indicating a confinement-induced decoupling of smectic and nematic order parameters. Preliminary NMR results show that in the largest Millipore size studied, the behavior is similar to bulk's; in smaller voids, there are dramatic differences from bulk that emphasize the dominating role that the fibrous surfaces begin to play.

The phase ordering kinetics of various liquid crystalline systems turning from a disordered to an ordered phase induced by a rapid temperature quench was investigated. The process of phase ordering as evolution of large scale structure can be described by the growth of a characteristic length L. The exponents n of the universal growth law L(t) approximately tⁿ have been determined. For the early stage of the phase ordering process we obtained values for n between 0.5 and 1 dependent on the depth of the temperatures quench. These results for mainly spherical shaped nematic and S_B-germs are discussed in terms of the Allen-Cahn- theory for the movement of an antiphase boundary. 0.5 as a lower limiting value confirms the classical theory while 1 as an upper limiting value can be explained by the introduction of a volume driving force. The late stage was investigated in different Blue Phase systems. We obtained values for n between 0.1 and 0.2 dependent on the various systems but not dependent on the quench depth. The exponents lie distinctly below theoretically predicted values. The role of broken symmetry is discussed critically.

A homeotropic nematic liquid crystal was exposed to low frequency oscillatory shear. In the presence of rectilinear shear a stationary roll pattern was found above a critical amplitude. In case of elliptical excitation a spatially nonuniform slow rotation of the director was observed, which lead to the propagation of the so-called phase waves in two different systems: in a two-phase system and in a homeotropic nematic layer in the presence of a destabilizing external electric filed. Phase waves also have been observed in the ultrasonic frequency range at much smaller shear amplitudes.

The liquid crystals with Cr-SmC-N phases were studied under high pressure by x-ray method. Also intercalated SmC and SmA phases were investigated, relatively strong compressibility of the smectic layers in both phases was found. The columnar mesophases under pressure were studied as well. In hexagonal Dh phase the columnar distance was nearly pressure independent while in rectangular Dr mesophase pressure increases interdigitation of the molecules from neighboring columns.

An x-ray investigation has been performed on five new 2,5- disubstituted 1,2,4-oxadiazoles with reversed structures containing 4-amylbiphenyl-, trans-4-amylcyclohexylphenyl- and 2-halophenyl- as substituents. The aim was to confirm the data about the phase sequence, obtained via polarizing microscopy and differential scanning calorimetry, and to measure the structural parameters. Through x-ray diffraction technique, all substances showed only the nematic mesophase. Moreover, it was proved that some enthalphy variations previously attributed to crystal-crystal transitions are in fact due either to the rearrangement of the lattice or to the coalescence of the grains. However, for some substances, a second crystalline from c' appeared at the melting point, on cooling from the isotropic phase. C' turned out to be different from the starting form C₁ of the sample, which had no thermal cycle before.

Two series of cholesteryl derivatives comprising esterimide group with oxyethylene or methylene chains were synthesized. Additionally, some monomeric and dimeric compounds in which the esterimide groups were substituted by succinate ones have been prepared. Liquid crystalline properties of all compounds have been studied by means of DSC, polarized optical microscopy and x-ray diffraction methods. It was found that all esterimides with oxyethylene tails form the chiral nematic N^* phase and bilayer smectic C₂* phase. Theirs hydrocarbon chain analogues with the number of carbon atoms in the chain n > 2, form the N* phase and monolayer SA) phase. The esterimides with very short tails are monotropic and tend to form bilayer smectic A and C phases. Substitution of esterimide group by less polar succinate group leads to reduction of mesomorphic tendencies of dimeric and monomeric compounds.

Bicomponent mixtures of 4-cyanobiphenyl-4'-yl 4- heptylbiphenyl-4-carboxylate and 4-heptyloxy-4'- cyanobiphenyl or 4-dodecyloxy-4'-cyanobiphenyl have been studied using small angle x-ray diffraction technique. The layer thickness in the induced smectic A_d phase and the apparent molecular length in the re-entrant nematic phase have been determined with temperature and concentration changes. The concentration variation of layer thickness hows a small maximum at the concentration where the smectic A_d phase is the most stable. For mixtures showing re- entrant nematic phase the order parameters were calculated.

Two series of binary mixtures 8CBB-nTPCHB and 9OBCAB-nTPCHB were investigated by the thermo-microscopic method. The structure of the smectic A₁ phase of compounds of the nTPCHB homologous series with short aliphatic chains is similar to the structure of the smectic A₁ phase of compounds with terminal-CN group and the structure of nTPCHB compounds with long aliphatic chain is similar to the smectic A_d phase. The change of the structures in compounds of the nTPCHB series proceeds in a continuous manner.

Perfluorinated alkyl chains were introduced into proton donating molecules which are able to form hydrogen bonded associates with suitable proton acceptors. Mesophase induction and stabilization were observed. Liquid crystalline associates were proven by microscopic investigation and phase diagrams. Smectic phases are stabilized in rod-like and laterally branched mesogens. The clearing temperatures are much higher than for the analogous nonfluorinated associated.

Phase situation of homologous series of di-alkyl-di-methyl ammonium bromides represented by the general formula: 2C_nN⁺2C₁Br^-, with n equals 10, 12, 14, 16, 18, was investigated by means of differential scanning calorimetry and optical microscopy methods in the temperature range 20-180 degrees C. A more complex polymorphism as already reported was detected. All the compounds studied show at least tow anomalies on the DSC curves. The high-temperature phase which appears below the isotropic phase has lancet-like dendritic texture which can be attributed to SmB phase. The enthalpy changes at the transitions were calculated.

Dialkyldimethylammonium halides are known for their applications as commercial detergents and for their membrane-mimetic properties. They display both thermotropic and lyotropic liquid crystalline properties. In this work we establish the T(p)-phase diagrams of two representatives, namely didodecyl- and ditetradecyl-ammonium bromides. The transitions between crystal, smectic Ii and smectic I phases were recorded using a high-pressure differential thermal analysis device. For both compounds the stable range of smectic II phase is pressure-limited, resulting in a triple point crystal/smectic II/smectic I. Enthalpy changes at ambient pressure have been determined with the aid of a commercial heat flux differential scanning calorimeter. Volume changes were calculated from the slopes of the transitions lines, employing the Clausius Clapeyron equation.

Three ligands with different number of carbon atoms in alkoxy chain, their Cu(II) and Ni(II) metallomesogens were synthesized. Absorption, linear dichroism spectroscopy measurements in visible region and x-ray diffractometry measurements at heating-cooling cycles were performed. An influence of organic groups and Cu(II), Ni(II) ions on thermodynamic properties have been discussed.

A ligand and three metallo-organic complexes containing Nd³⁺, Tb³⁺ and Er³⁺ ions were synthesized. Absorption linear dichroism spectroscopy and domain structures investigations plus x-ray diffractometry measurements at heating-cooling cycles were performed. An influence of a rare earth metals on LC thermodynamic properties have been discussed.

Phase states of liquid crystalline (LC) systems consisting of non-chiral smectogenic ester and structurally similar smectogenic chiral dopant, N-[4-(4-n- nonylphenyl)benzoyloxy]benzylidene S-1-benzylethylamine, have been studied. In all investigated LC systems, the twist grain boundary smectic A (TGB_A) and smectic C (TGB_C) phase occur between the cholesteric and SmA phases and between the cholesteric and SmC* phases, respectively. The effect of matrix smectogenity on the TGB phase regions has been established. For the chosen LC system with varying ratio of the optically active and racemic forms of the dopant at a constant total concentration, the experimental dependencies of TGB_C and TGB_A phase temperature ranges on a cholesteric helical twist have been obtained. The experimental results are interpreted within Renn's model.

The helical twisting power (HTP) of a homologies series of novel series of novel chiral binarphthol (BN) derivatives in open and bridged forms has been studied int ow different nematic solvents. The direct correlation between molecular structure and HTP was revealed: increasing the length of the substituents in 6,6' positions leads to the increasing of helical twisting power. Open-chain compounds display a significant decrease of twisting power on heating. The decrease of HTP is explained in terms of changing of the molecular conformation. The conformational properties of BN derivatives dissolved in a pentylcyanobiphenyl liquid crystalline (LC) matrix were determined by molecular dynamics simulation. Due to the influence of intermolecular interactions between the molecules of the LC matrix and the BN molecules, the conformations of the BN molecules in LC cell are found to change from transoid to cisoid on heating that results in decrease of observed HTP.

An unusual depression of phase transitions was observed in a polymer composite system, when 4,4'-bis(2- methylpropenoyloxy)-biphenyl (BMB) was UV polymerized in a cholesteryl propionate matrix. Our analysis indicates that different chemical processes take place simultaneously during the photo polymerization. One is the polymerization of BMB leading to the formation of a polymer network. Independently from this, cholesteryl propionate suffered some chemical changes and, as main product, 7-hydroxy- cholesteryl propionate formed. This compound was isolated and its structure established by IR, NMR and MS spectroscopy.

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.

The influence of thermal neutron irradiation on the smectic- liquid-crystal properties of arachidic and elaidic fatty acids is investigated. These fatty acids are either precursors or constituents of biological membrane. Microstructural aspects and electric measurements are presented to determine the external voltage dependence of current intensity through the sample. A thermodynamic model, which is in good agreement with experimental data, is described.

Two broad groups of organosilicon polymers are reviewed, presenting different structural features. Some polysiloxanes and polysiloxanes, referred often to as condis crystals, do not contain any architectural elements of rigid rod- or disc-like type moieties, despite the fact, that these flexible chain polymers show an interesting mesomorphic behavior and generate columnar mesophase. The second group involves macromolecules with mesogens incorporated into main or side polymer chains. The advantage of using inorganic flexible backbones lies in lowering phase transition temperatures compared to many organic polymer systems.

A series of dimeric compounds with organosilicon spacers has been synthesized and studied by means of DSC, x-ray diffraction and polarizing microscopy methods. All compounds form the smectic A and nematic phases. The liquid crystalline properties of the dimers have been compared with those of side-chain organosilicon polymers.

IR spectroscopy was used to analyze the orientation behavior and in-situ photopolymerization of two mesogenic acrylates in the chiral smectic I phase and in the S_A phase, respectively. The orientation parameter, S, was determined using unpolarized radiation and by comparing the spectra of the mesophase with those of the isotropic phase. The type of alignment was deduced from the observation that the absorption is higher in the mesophase than in the isotopic phase for vibrations perpendicular to the mesogenic core. The change in the relative intensity of the bands with opposite direction of transition moments showed that the long axis of the mesogenic cores is tilted from the direction of the incident beam.

Conformational and optical properties of the molecules of alkylphenylsiloxane co-polymers and a number of ring- containing organosiloxanes have been studied. It was established that the high content of phenyl side group linear molecules and the interaction between them determine on the molecular level the main features of molecular conformation: increase in equilibrium rigidity and high optical anisotropy. These molecular characteristics are in good agreement with those of the polymer on the supermolecular level.

The orientational order of a nematic liquid crystal side group copolymer aligned in a magnetic field has ben investigated using ESR spectroscopy. We find that the mesogenic groups are highly oriented parallel to the director whereas the polymer backbone appears to be randomly distributed or disordered. The EST spectra of both spin probed and spin labelled systems were recorded in their glassy nematic states at room temperature as a function of the angle between the director and the magnetic field. The spectra for the spin probe dissolved in the copolymer show that the spin probe has a high orientational order and by implication that the mesogenic side groups are highly ordered. The EST spectra of the spin labelled copolymer indicate that the orientational order for the label and so presumably the polymer backbone is zero.

Two series of thermotropic liquid crystalline main-chain fluorine-containing polyesters, based on fluorinated alkylene diols and terephthaloyl-bis-(4-oxybenzoylchloride) and its analogue containing nitrogroup in the central phenylene ring were studied by polarizing microscopy, differential scanning calorimetry, viscometry, isothermic diffusion and electric birefringence methods. The upper limit of the fluorinated spacer length, when these polyesters lose their ability to form mesophase was found. It was established that the melting temperatures of the polyesters did not decrease with increasing number of CF₂ groups in the spacer. The nematic textures of the investigated polymers were observed in cross polarizers. The differences in conformational and electro-optical properties of polyesters with fluoro- and hydrocarbon spacers were found. The dipole mechanism of the polyester molecules orientation in electric field was revealed. Two series of low-molecular-weight liquid crystalline compounds were synthesized to compare their properties with those of the polymers of similar structure. These esters exhibited a tendency to form smectic phase. The influence of the alkyl end group length on the mesomorphic properties of the esters was found.

The differential scanning calorimetry (DSC) and the thermo- optical analysis were used to study the phase transitions of 2-(hydroxypropyl)cellulose (HPC) and three thermotropic liquid crystalline derivatives of the HPC: the propionyloxy ester, the hexanoyloxy ester and the cyanoethylated derivative. All the investigated derivatives show in the heating scan of the DSC an endothermic transition in the range of temperature of melting of the birefringent phase. Additionally the cyanoethylated derivative of HPC reveals the exothermic phase transition below the melting temperature of the birefringent phase. This phase transition is connected with a large increase of transmission of polarized light. The results are discussed in terms of polarity HPC and their derivatives. The decrease of the polarity of the nonmesogenic side chains of HPC shifts the clearing temperature towards lower values and extends the temperature range of the mesophase.

The temperature dependence of hydrodynamic properties of three new LC comb-like poly(alkoxy-4- ethylphenylbenzoate)(methyl)-siloxanes) with different alkyl spacers between the backbone and the mesogenic side groups, and low-molar-mass compounds as models, analogous to macromolecule side chains has been investigated. Temperature-reversible aggregation of the molecules of these compounds in benzene solution was observed at temperatures below 26 degrees C. This phenomenon was found to depend on the degree of bonding of thermotropic mesogens to the backbone chain and on the aliphatic spacer chain length.

Side-on polysiloxanes bearing laterally branched mesogens were synthesized. The mesogens have a bulky lateral branch containing an aromatic ring with an alkenyl chain in para- position, which enables a coupling to the polysiloxane backbone. Surprisingly, reaction with poly-H-siloxane can cause increasing or decreasing of the clearing temperatures. The dimension of the mesophase destabilization was found to be up to 27 K. By systematic investigations of this unusual effect we could prove a clear dependence on steric proportions. Especially, the relation of the length of the terminal alkyl chains R¹ and the length n of the flexible aliphatic spacer is of influence.

The polymer P8*5 has a frustrated phase behaviour. It shows either the sequence of mesophases g 3 1-35°C S 44°C SA* 47°C i or g 3 1-35°C TGBC 47°C i. It is not completely understood yet under which conditions one of the phase sequences is prefered. Both phase sequences are kinetically stable and reproducible. Similar behaviour has been observed earlier1'2 for the acrylic copolymer C37, but no detailed study ofthe two phase modification was carried out. The "subcritical" phase condition of the substance should be the reason for extremely low driving voltage values of optical switching in S* p1c ( O.2V4tm) and for extremely low untwisting voltages (0.5 - 1.5V/iim), as well as for the low clearing point values and for the existence of the switchable Sc p close to room temperature. The siloxane main chain of the polymer should be less preferable for the formation of a highly twisted, weakly birefringent TGB-like phases, as compared with the methacrylic one, since for the latter such a frustration can be achieved only by addition of63% of nonchiral moieties to the structure ofthe copolymer"2. Keywords: ferroelectnc polymer liquid crystal, tilt angle, pyroelectric coefficient, hysteresis, X-ray

We investigated the interaction between polymer network, which is prepared in liquid crystal host, and liquid crystal. It was found that the polymer network gave a rough parallel alignment because of the uniform alignment of liquid crystalline host. The polymer network formed in an electric field shows strong influence on the orientation of the liquid crystals. Higher tilt angles of liquid crystal can be achieved because of the stabilization of polymer network.

A series of liquid crystalline binary polymer blends consisting of P1 with a dimethylamino group as an electron donor and P2 with a nitro group as an electron acceptor was prepared and investigated by using DSC, optical polarized microscopy and x-ray diffraction. The binary mixtures of their model compounds 4-hexyloxy-4'-nitro-azobenzene (MA) and 4-hexyloxybenzylidene-4'-(N,N-dimethylamino)-aniline (MD) were also prepared and investigated. The results show that these binary mixtures have good miscibility and exhibit broader mesophase ranges than that of the individual acceptor and donor, which are considered to be caused by the interactions between the electron donor and acceptor groups. For example, the isotropic temperature of the 1:1 polymer blends is 441.5K, which is 48K higher than the calculated value based on the composition without any interaction, while its melting point is 28K lower than the calculated value. And for the 1:1 mixture of MA and MD, the isotropic temperature was 20 degrees C higher than the calculated value and the melting point was 19 degrees C lower than the calculated value.

The paper deals with an unusual Kerr constant behavior of comb-like liquid crystalline polysiloxanes in solutions of organic solvents near the critical temperature of stratification. There were observed Kerr constant grows by three orders in magnitude and sign inversion in this thermal region. Pretransitional phenomenon in solutions was explained by formation of a stable aggregate with a high degree of intermolecular ordering. It was shown that a sign of supermolecular Kerr effect is directly connected with the polar properties of polymer mesogenic groups.

Bis [((omega) -(4'-cyanobiphenyl)-4-yl)oxy-n- alkyl]norborn-5-ene-2,3-dicarboxylate was polymerized via ring opening metathesis polymerization. Two distributed polynorbornene derivatives, both of cis configuration, with different length of side-chain were studied. The influence of thermal history on the smectic phase stabilization, position and shape of the glass transition with temperature and on the relaxation process is shown. Glass transition temperatures enthalpies of isotropization and average layer spacing were calculated. Although, the rather flexible spacer between the mesogenic group and the main chain seems to be sufficient to partially decouple the mobility of the main chain from that of the mesogenic group, the influence of a backbone chain structure is still significant for polymer properties, especially in bulk. The measured layer spacing doe not correspond to double length of the side chain which suggests that either the side chains are not fully extended or some overlapping of CN tails occurs.

Dielectric relaxation and molecular mobility have ben investigated over the frequency range 60Hz-1MHz between 160 degrees C and 150 degrees C for smectic side-chain oligoacrylates with 4-cyanazobenzene mesogenic side groups and methylene spacers of different length. The studied oligomers were oriented by electric or mechanic fields. In the range of subglass temperatures two dielectric processes were observed - the (gamma) ₁ and the (beta) . The (gamma) ₁ process reflects the local motion of the spacer groups and the (beta) process is connected with the local motion of the mesogenic moieties. the molecular mobility of the (gamma) ₁ process increases with the spacer lengthening but at the same time in the case of the (beta) process the mobility is not changed. In LC state near T_g transition, the temperature-frequency dependencies of dielectric losses show two cooperative processes, the (alpha) - an the (delta) , related to the reorientation of the transverse or longitudinal components of the dipole moment of the mesogenic group, correspondingly. The preliminary orientation in external electric or mechanic fields leads to the establishment of planar or homeotropic orientation of the side mesogenic groups. The order parameters of oriented films were calculated. It was shown the planar or homeotropic orientation of mesogenic groups did not influence on relaxation times of the observed dielectric processes.

Dozens of poly(amic acids) from selected aromatic diamines and dianhydrides were prepared in the first step of the classical two-step polycondensation. Polyimide layers on different surfaces were obtained by the poly(amic acids) imidization. Some of mechanical properties of these layers were tested. Some correlations between these properties and chemical structure of them wee noticed and discussed.

We have prepared PDLC with mixtures of polyisobuthylmethacrylate and CN934D60 at a constant percentage of TN0623 nematic liquid crystal and change in the polymers' relative composition. Two step polymerization CN934D60 concentration and polymerization sequence. When the relative concentration of CN934D60 is increased the scanning electron microscope analysis reveals a transition from 'swiss cheese' to 'polymer ball' type morphology.

Polymer-dispersed liquid crystal films, using polymethyl methacrylate and nematic liquid crystal E3 were obtained. The electro-optical effects were investigate using He-Ne lasers of different powers and a.c. electric fields of different frequencies applied across the composite film. The measurements of the transmitted light intensity through the composite film were carried out without any polarizers. At low frequencies,the emergent optical signal is modulated in amplitude, doubling the frequency of the a.c. driving field. In the kHz frequency range, the decrease of the fluctuations of the transmitted light with the increase of the frequency was noticed. The conductive properties of the polymer dispersed liquid crystal composite films and the contribution of the non-linear effects to the electric conduction were determined.

This work extends the authors' investigation son liquid crystalline epoxy resins prepared from diglycidyl ether of 4,4'-dihydroxybiphenyl and aliphatic dicarboxylic compounds or difunctional aromatic compounds. Syntheses and properties of these liquid crystalline epoxy resins are described elsewhere. In this paper a study on the curing reaction of two from the above mentioned liquid crystalline epoxy resins is presented. Ortho-tolylbiguanide was applied as the curing agent. The curing reactions were investigated by differential scanning calorimetry, microscopic observations and IR spectroscopy. Depending upon the temperature program of curing, it was possible to obtain polymeric networks with liquid crystalline order.

Novel liquid crystalline poly(urethane-urea)s (PUUs) were synthesized from 2,4-tolylene diisocyanate, 4,4'-bis(2- hydroxyethoxy)biphenyl and poly(oxypropylene)diamines (Jeffamine). The poly(urethane-urea)s were characterized by FTIR, GPC, DSC and polarizing microscopy. The mesomorphic properties of the polymers were investigated as a function of their molecular structure by changing alternatively the molecular weight of Jeffamine or the initial diol and diamine composition. The applied structural modifications allowed us to obtain thermotropic PUUs exhibiting mesomorphic behavior in a wide temperature range along with the PU exhibiting no liquid crystallinity.

The monomers for poly(ester imides) synthesis have been prepared from selected anhydrides and amino acids. The groups of poly(ester imides) has been synthesized by reaction of carboxyimides and diols. Thermal stability of selected polyimide samples has been tested. The liquid- crystalline properties have been evaluated by DSC method. The depth of nematic liquid crystals alignment of the polyimide layers using the interference wedge method has been examined. The relationship between the chemical structure of synthesized poly(ester imides) and some of their properties is discussed.

Physical and biophysical mechanisms of mechanosensitivity of cell membranes are reviewed, including: elasticity and flexoelectricity of cell membrane complex, pore formation in the lipid matrix, capacitance and conductance variations, mechanosensitive ion carriers and ion channels. The possible active role of the liquid crystalline lipid matrix in the mechanoreception is underlined. The review goes on to the patch clamp technique as a tool for mechanosensitivity studies. The techniques for generation of static strains and dynamic curvature variations of membrane patches are considered. A unified model for description of both stress-activated and stress4nactivated ion channels under static strains is described. Stress sensitive pores in lipid-peptide model membranes are demonstrated as well. Particular point is made about flexoelectric phenomenon as a mechanism of direct conversion of mechanical stimuli into electric signals, e.g. in hearing. Studies of flexoelectricity of model lipid membranes, lipidpeptide membranes and biomembranes containing ion channels are reviewed. Finally, future applications of liquid crystal principles to mechanotransduction in living cell membranes are outlined. Key words: Mechanosensitivity - Mechanotransduction - Cell membrane complex - Ion channels Stress sensitivity modelling - Lipid matrix - Cytoskeleton - Mechano-electric phenomena - Flexoelectricity - Model membranes Mechanosensors

On the basis of Monte Carlo simulations and elastic theory it has recently been shown that chiral symmetry breaking can occur for non-chiral molecules. Up to now, such phenomena have experimentally been observed only in thick nematic films on liquid surfaces or in Langmuir monolayers. Here, we report the first case of chiral defects in lyotropic system of the benzenehexamine derivatives 1c or 1d in linear alkanes.

Pure fatty acids and mixtures, which can be found in the biological membrane, were prepared and studied in interaction with electric, magnetic and optic fields, under different temperature conditions. All the samples displayed a smectic C liquid crystalline texture, and ferroelectric behavior. The nonlinear electric and optic features of their response have been emphasized and correlated. Theoretical considerations are meant to explain this behavior, in connection with the living matter processes.

The synthesis and investigation of mesomorphic properties of 5,15-di-4(p-oxyphenyl)octamethylporphyrin derivatives were carried out to study the influence of molecular structure geometry on thermotropic and lyotropic mesomorphisms in a number of organic solvents.

In order to determine the influence of substituents in palladium organyls of type 1 on the area of lyomesophase existence, the behavior of 10,12 or 14 homologues of 1(1a-c) in pentadecane has been investigated. These data are compared with the phase behavior of the binary system palladium organyl 1d/pentadecane, in which the substituent R equals CH₂CH(C₁₀H₂₁)₂ is branched and contains twelve carbon atoms in the main chain.

Dependence on a n applied external electric field of the current intensity through samples of fatty acids with mesomorphic behavior was investigated. The time dependence of intensity for a potential step applied to the sample, was used to determine the specific space charge. Electric conduction was analyzed based on the experimental results.

The alignment effect of erythrocytes in liquid crystal media with different optical and dielectric anisotropies has been investigated. The effect has been compared with the Froelich interaction.

The lipids of the stratum corneum fulfil a vital barrier function for the mammalian body. Cermides IV and cholesterol as the main components of stratum corneum as well as their mixtures have been investigated using Langmuir method at the air-water interface. Different 2D phases have been characterized by the aid of (Pi) /A isotherms and by fluorescence micrographs. The properties of films strongly depend on the composition of the mixtures. The Langmuir- Blodgett technique (LB) has been used for the preparation of supported monolayers. These LB layers have been investigated by atomic force microscopy and cyclic voltammetry. It could be shown that addition of small amounts of cholesterol to ceramides IV results in an improvement of the properties of the films: a decrease of electrical capacity of the layer and a decrease of the defect density of the film. In a film containing 50 mol percent ceramides IV an increase of the capacity and phase separation in the surface film has been observed.

It is a well known fact that the increasing of heavy metal concentration in biological tissue leads to serious pathology changes in the human organism. As blood is the lyotropic liquid crystal the attempts to use the electrophysical methods of liquid crystal investigations for the discovery of blood parameters changes were carried out. The experiments were carried out in the magnetic field of 1,3 T with frequency 1 kHz. The investigations conducted in the magnetic field showed that the increase of concentration of heavy metals in blood result in the linear decease of conductivity anisotropy and dielectric anisotropy values. On the basis of the obtained results a new hypothesis of heavy metal influence on the electrophysical parameters of blood, as well as an express-method of blood diagnostic of heavy metal concentration have been proposed.

In this paper we report the investigation, performed via proton- and deuteron-NMR on samples of trans-4-butyl- cyclohexane carboxylic acid (C₄), and via proton-NMR on samples of a cis-trans mixture of the same substance, containing 12 percent cis-isomer (C_4.12). The aim of the research was to study the dimerization process at different temperatures via NMR technique. As it is known, only the presence of a conveniently large proportion of closed dimers of trans-isomer allows the nematic mesophase to be established. The results obtained with proton-NMR on C₄, approaching on cooling the clearing point, revealed, as expected, the increasing of the amount of closed dimers. Just below the clearing point, in a range of a couple degrees only, the presence of open dimers was detected. On the contrary, down into the nematic phase, only closed dimers turned out to be present. The results obtained via deuteron-NMR on C₄, deuterated in the hydroxy position, are consistent with the proton-NMR data. Moreover, the deuteration was found to strongly influence the bonding energy, thus forcing the nematic phase to appear at definitely lower temperature. Furthermore, proton-NMR investigation of C_4.12 samples showed a clearing interval instead of a clearing point. These results suggest a phase separation, which is in agreement with our microscopy observations. The presence of open dimers in a small temperature range, just below the clearing interval, is also confirmed. But we didn't succeed to obtain any information about mixed dimers.

A mesomorphic long-chain tetraphenylporphyrin was investigated on the visible absorption and fluorescence spectra and the fluorescence lifetime was measured through the phase transitions. All results indicate that the low- temperature lamellar mesophase has face-to-face molecular arrangement, through the high-temperature one does not as the proposed structures based on the powder x-ray diffraction studies.