This article reports new results on mesomorphic properties of 1,3-phenylene bis{4-[(4-heptyloxybenzoyl) sulfanyl] benzoate}, from the homologous series of banana-shaped resorcinol-based thioesters, referred to as 7OSOR, synthesized by us. The 7OSOR compound has got three enantiotropic smectic phases. At higher temperatures, 7OSOR exhibits the B6 phase and the B1 and SX phases at lower temperatures. The mesomorphic properties were studied by three complementary methods: Differential Scanning Calorimetry (DSC), Polarized Light Optical Microscopy (PLOM) and Transmitted Light Intensity (TLI). X-ray diffraction, static dielectric permittivity and electro-optic studies (EO) were also carried out.

Two fluorinated compounds: 3-(2-fluoroctyloxy)-6-(4octyl-phenyl) pyridine (FOOPP) and 3-(fluornonyl)-6-(4-heptyloxy-phenyl)pyridine (FNHPP), synthesized by E. Merck Company in earlier 1990s, which show a pronounced increase of spontaneous polarization at the SmC*-hexatic SmI* transition have been reinvestigated. In this contribution we shall present calorimetric, dielectric and electro-optic behavior of two perfluorinated compounds which display enhanced high spontaneous polarization in enantiotropic hexatic phases. Phase transitions have been studied by DSC, polarizing microscopy, X-ray diffraction, and reversal current method, and molecular and collective dynamics – by dielectric spectroscopy. Spontaneous polarization measurements vs. temperature show that the SmI* phase of FOOPP exhibits almost 3 times larger spontaneous polarization than the high temperature ferroelectric SmC* phase.

Two and three ring achiral esters being the derivatives of benzoic or biphenylcarboxylic acid were prepared. Their phase transition temperatures, enthalpies and smectic layer spacing were investigated. The compounds have extremely high clearing temperatures and clearing enthalpies. The layer spacing of the smectic A phase is equal to the molecules length. The synclinic smectic C phase or anticlinic one exhibit small tilts.

Two chiral liquid crystalline compounds have been investigated, namely 4-(1-methylheptyloxycarbonyl) phenyl-4′nonylbiphenyl-4-carboxylate (MHPNBC), 3-(2-fluor-octyloxy)-6-(4octyl-phenyl) pyridine (FOOPP) to study the SmA∗–SmC∗ transition. For both substances strong electroclinic effect is observed in the SmA∗ phase what indicates that it is the so-called de Vries SmA∗ phase. To study the paralectric-ferroelectric de Vries type transition electrooptic, dielectric as well as SAXS methods have been applied.

Searching for compounds which could be useful as modifiers of smectic C mixtures, we have synthesized four homologous series of three ring dioxanes, 2BBD, 5BBD, 2CBD, and 5CBD. Their phase transition temperatures and enthalpies were measured and their liquid crystal phases identified. Compounds belonging to series n-BBD form smectic B(cr) phases for shorter alkyl chains, and smectic B(cr) and A phases, for longer chains. Compounds belonging to the n-CBD series exhibit the smectic A phase, but those with longer alkyl chains have exclusively smectic B phases and those with short tails have other low temperature, highly ordered smectic phases. The compounds were added to smectic C mixture and it was found that some can be useful as dopants. Compounds with longer alkyl tails in the molecule are more suitable for this purpose; the type of ring in the core is less important.

The phase situation in a few members of 4,4'-dialkylbiphenyl homologous series were investigated. Different orthogonal smectic E phases existing in the temperature range below the smectic B-cryst phase were observed. The simultaneous existence of three different smectic E phases in 4-pentyl 4'-hexylbiphenyl by thermomicroscopic, DSC and rentgenographic methods was confirmed. The miscibility studies were used to assign these phases to other smectic phases existing in other members of this homologous series.

The compounds from the fluorinated nF6B (n = 1,2,3,4,5,6,7) homologous series were investigated by means of optical, electrooptical, refractometrical, dielectric, densytometric, X-ray and IR spectroscopy methods. For some compounds being a subject of investigations a computer simulation of molecular properties were done. In our opinion high value of optical tilt Θo angle in comparison with a tilt angle obtained from X-ray measurements can be interpreted in terms of de Vries model of SmA* phases as well as of dimers creation process.

Phase transitions, smectic layer structure, helical pitch and electrooptical properties of recently prepared high tilted antiferroelectric compounds are characterized. The compounds enable to prepare broad temperature range (−20 to 100 °C) orthoconic antiferroelectric mixtures, having 45° tilt independent of temperature in broad temperature range, and exhibiting excellent contrast and grey level scale.

Homologous series of three ring esters (biphenylates and benzoates) - chiral (S), racemic (R,S) and achiral (either isopropyl or 4-heptyl chain) were tested by DSC, X-ray and electrooptic methods. It was found that in chiral, racemic and achiral homologous series with a 4-heptyl chain, the smectic A phase is a strongly tilted phase of de Vries type, and molecules in the anticlinic phase are highly tilted within the layers (up to 45 degrees). The homologous series with an isopropyl chain gave a normal smectic A phase and low tilted synclinic or anticlinic phase. Chirality does not influence the smectic layer thickness or the molecular tilts in the smectic synclinic or anticlinic phase, but strongly influences the ability to form anticlinic order. The ability of the molecules to adopt anticlinic order is suppressed when a permanent helical structure or strong steric hindrance is absent.

Two series of three ring esters with chiral chain (derivative of (S)-octanol-2) and achiral chain (the swallow type) with high tilted synclinic and anticlinic phases were chosen to studies. The aim of presented studies was to find how the changes of different molecule units influence the mesomorphic properties of the compounds (temperatures, enthalpies and the sequence of phase transitions) and to find members with the best properties for mixture formulation. The compounds were studied by polarising microscope, differential scanning calorimetry, miscibility and X-ray diffraction methods.

Homologous series of chiral (S) 4-(1-methylheptyloxycarbonyl)-phenyl and achiral 4-(4-heptyloxycarbonylphenyl 4-(perfluoroalkanoyloxyhexyloxy)biphenylates or 4-(alkanoyloxyhexyloxy)biphenylates, chiral (S) and racemic (R,S) 4′-(1-methyl heptyloxycarbonyl)biphenyl-4-yl 4-(perfluoroalkanoyloxyhexyloxy)benzoates or 4 (alkanoyloxyhexyloxy)benzoates have been prepared and their phase transitions have been investigated by DSC and polarizing thermomicroscopic methods. Moreover the temperature dependence of interlayer spacing by a small angle X-ray diffraction method has been studied. The chiral and achiral members exhibit a SmC anti. phase, while racemic members only exhibit SmC phase. Fluorinated compounds have lower melting points, lower melting enthalpy and broader range of the SmC anti. phase than earlier prepared series with shorter spacer group (CH 2 ) m , m < 6. They are very useful components for the formulation of orthoconic (interlayer tilt 90°) antiferroelectric mixtures with temperature range from (−20°C) to 100°C.

Four compounds with the isothiocyanate terminal group (–NCS) in tolane or biphenyl molecules, revealing E phase in a broad temperature range, have been investigated by means of the DSC, polarizing microscope, miscibility and X-ray methods. The investigations have confirmed that internal smectic E phase in those compounds was not identical and it has been characterized by different distortions of the orthoconic cell and interlayer correlation.

Chiral, smectogenic pendant groups have been covalently attached to cyclic oligosiloxanes by hydrosilylation. Differential scanning calorimetry, optical polarising microscopy, and X-ray diffraction measurements reveal liquid crystalline properties for all synthesized monomers and oligomers. The monomers, which differ by the nature of the rigid mesogenic core or end groups, showed enantiotropic smectic A phases. Almost all of cyclic oligosiloxanes present enantiotropic chiral smectic C phases. The mesomorphic range of these oligomers is greatly enhanced relative to the type of monomers and the ring size as well.

Three new series of N-alkyl-substituted ester imide derivatives, which differ in the polarity of their mesogenic groups; specifically, either cholesteryl, 4′-undecyloxybiphenyl or 4′-cyanobiphenyl, have been synthesized. For the N-alkyl-[4-(cholesteryloxycarbonyl)]phthalimides the chiral nematic N* phase and the monolayer SmA1 phase have been observed up to the dodecyl homologue. The pentadecyl and octadecyl members of this series show only the SmA1 phase. The monolayer smectic A1 phase was also observed for all members of the N-alkyl-4-[(4′-undecyloxybiphenyl-4-yl)oxycarbonyl]phthalimide series while the longer homologues (with n>5) exhibited SmA–SmC dimorphism. In the case of the N-alkyl-4-[(4′-cyanobiphenyl-4-yl)oxycarbonyl]phthalimides, the short homologues exhibited only a nematic phase, while for the butyl homologue in addition to the nematic phase the bilayered SmA2 phase was observed. The smectic phase vanished for the pentyl and hexyl members but reappeared as a partially bilayered smectic Ad phase for the longer homologues.

Recently the investigation in the field of display technology has been boosted by the availability of new materials. The mostly promised solution for that looks to be based on an antiferroelectric liquid crystalline materials (AFLC). The new group of materials consisting of a fluorinated terminal chain has been recently synthesized in Poland [1]. Such key factors as the optical indices, apparent tilt angle, and structural properties and electrooptical performance of these materials have been studied. The effect of the bend (hockey stick like) molecular shape has been assumed as a factor leading to an high apparent optical tilt angle. The relation between the apparent optical tilt angle and the tilt measured using XRD method and its change with the temperature has been explained.

Recently the investigation in the field of LCD technology has been boosted by the availability of new materials. The new group of fluorinated mesogens has been recently synthesized in Poland(1). In this work we have been focused on investigations of properties of materials having the broad temperature range of antiferroelectric phase. Such key factors as apparent tilt angle and structural proper-ties and electrooptical performance have been studied by means of electrooptical and X-ray methods. The bend molecular shape and the presence of fluorinated tail has been assumed as a factor leading to an extremely high apparent optical tilt. The length of the fluorinated chain seems to affect the mesogenic behavior.

Mesomorphic properties (phase transitions enthalpies and temperatures) and the dependence of smectic layer spacings upon reduced temperature for eight homologous series of three ring ester such as: (S)-(+)-4-(1-methylheptyloxycarbonyl)phenyl or (S)-(+)-4-(1-methylheptyloxycarbonyl)-3-fluorophenyl or (S)-(+)-4-(1-methylheptyloxycarbonyl)-2-fluorophenyl 4'-(perfluoroalkanoyloxyhexyloxy)biphenylates and 4'-(alkanoyloxyhexyloxy)biphenylates, and (S)-(+)-4-(1-methylheptyloxycarbonyl)biphenyl-4-yl 4'-(perfluoroalkanoyloxyhexyloxy)benzoates and 4'-(alkanoyloxyhexyloxy)benzoates were described. The terminal chain fluorinated compounds have SmC*(anti)-SmC*-SmA-Iso phase sequence and a high tilted (orthoconic) anti ferroelectric phase in broad temperature range.

The pressure-temperature phase diagram of 4′-tetradecyl-4-cyanobiphenyl (14CB) up to 220 MPa (2.2 kbar) and between 320–400 K was established using DTA. The temperature range of the smectic A (SmA) phase slightly increases with pressure. The layer spacing d at 1 atm was determined as a function of temperature using X-ray diffraction. It was related to the molecular length l by the ratio d/l ˜ 1.4. The dielectric relaxation measurements in the isotropic and smectic Ad phases of 14CB at 1 atm were performed in the frequency range 10 kHz-3 GHz. Contributions from both principal rotational motions, i.e. around the short and long molecular axes, were separated. The relaxation measurements under high pressure in the SmA phase covered the low frequency process. The longitudinal relaxation time τ1, characterizing the molecular reorientations around the short axis, was analysed with respect to the pressure and temperature dependences, giving activation volumes, Δ# V = RT (∂ ln τ1 / ∂p)T, and activation enthalpies, Δ# H = RT(∂ ln τ1 / ∂T -1)p, respectively. Surprisingly, all the activation quantities characterizing the rotational motions of 14CB molecules under different conditions are nearly the same as those determined recently for the much shorter homologue, 8CB. This indicates that the 14CB molecule is in fact relatively short due to conformational motions of the alkyl tail.

Pressure has a specific influence on the light scattering in those liquids in which all molecules have an unsaturated double bond C=C. Strong changes of intensity of transmitted and scattered light in oleic acid were observed during its transition to the high-pressure phase. In this paper, local order in liquid of oleic acid has been studied using the X-ray diffraction photographic Laue method. Experiments were run at room temperature under atmospheric pressure as well as under pressures up to 0.25 GPa. At pressures above 0.2 GPa a strong increase of ordering of molecules, similar to a smectic liquid crystal phase, has been observed. This confirms results obtained previously by studies of light scattering under high pressure.

The novel esters of (E)-3-phenoxyacrylic acid have been prepared and their mesomorphic properties have been investigated by means of polarised light microscopy, differential scanning calorimetry and X-ray diffraction measurements. The influence of molecular structure on mesophase formation has been studied.