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We present a new series of bent-core liquid crystals possessing a lateral substituent in the apex position of the central core and a terephthalate connecting unit in one elongating side arm. The synthesised materials have been studied by polarising optical microscopy, differential scanning calorimetry, dielectric spectroscopy and X-ray diffraction. Electro-optical studies have also been performed to confirm the character of the identified polar smectic phase. We document that materials substituted with fluorine exhibit polar synclininic antiferroelectric phase, for homologues with longer terminal alkyl chains, this SmCSPA phase is accompanied with a high-temperature SmC phase. Our results document that the introduction of the aforementioned structural features triggers significant modification of the mesomorphic behaviour previously observed for similar compounds. [ABSTRACT FROM AUTHOR]

We report mesomorphic properties of non-chiral liquid crystalline molecules and study the effect of lateral halogen (fluoro, chloro) substitution in the molecular core and the length of terminal chains. We have prepared nine homologue series with the molecular core substituted at different positions with respect to the ester linkage group. Additionally, we have modified the length of both terminal alkyl chains (hexyl, octyl, decyl and dodecyl) symmetrically for both terminal chains. The effects of the lateral substitution and the chain length are analysed with respect of the possibility to reduce the transition temperatures and tune the properties of presented liquid crystalline molecules. [ABSTRACT FROM AUTHOR]

We report the synthesis and study of the mesomorphic behaviour for a series of bent-core materials based on 2-substituted 3-hydroxybenzoic acid as a central unit. Properties of the studied compounds are tuned by lateral substitution (F, Cl, CH3, NO2and CN) in the position 2 of 3-hydroxybenzoic acid and by the length of the terminal alkyl chain. All studied homologues exhibit at least one mesophase. Mesomorphic properties are established and compared with other 3-hyhroxybenzoic derivatives studied previously, with analogous orientation of ester linkages, laterally substituted at different position on the central core. The role of the substitution and the length of the terminal alkyl chain are discussed. [ABSTRACT FROM PUBLISHER]

Bent-core liquid crystals with a naphthalene central unit and an aromatic ring at the terminal position of molecular tails were synthesised with the aim of enhancing nanosegregation. It was found that the length of the spacer between the rigid core and the terminal aromatic moiety had a profound influence on the liquid crystal polymorphism. The homologues with short spacers exhibited nematic and columnar phases, whereas the homologue with long spacers exhibited a tilted lamellar phase with a liquid-like in-plane order, indicating an unusual morphology of the densely packed toroidal objects. The morphology can be changed to twisted ribbons by small additives adsorbed on the membrane surface. This is the first example of twisted ribbons constructed by a lamellar system with no long-range in-plane order. [ABSTRACT FROM AUTHOR]

We have prepared and studied new series of bent-core liquid crystals based on laterally substituted 3-hydroxybenzoic acid. The physical properties of the materials were tuned by the type of lateral substitution in the vicinity of the carboxylic unit. Further modification was achieved by reorientation of connecting ester linkages in the elongating side arms and by changing the length of terminal alkyl chains. The physical properties of the materials were determined by differential scanning calorimetry (DSC), polarising optical microscopy and for selected compounds by x-ray diffraction analysis. The introduction of fluorine as lateral substituent leads to the appearance of a lamellar or columnar mesophase. On contrary, methyl- or chlorine-substituted compounds are mostly crystalline. We have found a strong correlation between the size of the lateral substituent and the mesogenicity of the studied materials. [ABSTRACT FROM PUBLISHER]

Two series of new liquid crystalline lactic acid derivatives with a terminal ester group have been synthesised. The effect of this ester unit and the length of its alkyl chain on the mesomorphic and dielectric properties of the compounds exhibiting a broad temperature range of chiral smectic phases have been studied. We found that the mesomorphic behaviour and phase transition temperatures are strongly affected by the molecular architecture. Depending on the alkyl chain length in the terminal ester unit, the studied materials exhibited paraelectric smectic A*, ferroelectric tilted smectic C* and antiferroelectric smectic CA* phases over a broad temperature range. The physical properties of the compounds have been studied by optical polarising microscopy, differential scanning calorimetry, electro-optic measurements, small-angle X-ray scattering and dielectric spectroscopy. Furthermore, the homologues with short terminal alkyl chains showed a very small layer shrinkage at the transition from the orthogonal SmA* to the tilted SmC* phase, which is a characteristic feature of ‘de Vries-type’ behaviour. [ABSTRACT FROM AUTHOR]

Five series of compounds based on 2,4- and 2,7-disubstituted benzothiophenes have been prepared and studied with respect to their mesomorphic properties. The molecular structure was modified by prolonging the molecular arms (varying the alkyl chain length) and orientation of the ester linkages. It was established that the transition temperatures and the type of the formed phases strictly depend on the ester orientation and only limited number of prepared compounds exhibited mesomorphic behaviour. Based on X-ray patterns, columnar phases were identified and found that they have centred crystallographic unit cell differing in the lattice parameters for homologous compounds. Although the bend angle of the studied materials is around 90° only, they exhibited formation of phases typical of the bent-shaped liquid crystals. [ABSTRACT FROM PUBLISHER]

Six series of bent-shaped liquid crystals based on phenylthiophene central unit and differing in lateral substitution, the number and orientation of ester linkages and character of the terminal chain have been synthesised and studied. In comparison with the previously investigated biphenyl-based analogues, the presence of the thiophene unit results in a strong increase of transition temperatures and appearance of calamitic phases, the character of which depended on the structural changes of mesogens. [ABSTRACT FROM PUBLISHER]

A series of new bent-shaped liquid crystals based on 3-aminophenol was synthesised and their mesomorphic behaviour studied by differential scanning calorimetry, polarised optical microscopy and X-ray diffraction. Generally, the introduction of an amide group leads to a small increase in the clearing temperatures and stabilisation of the formed mesophases in comparison with the structurally related resorcinol based materials. The role of the linking group orientation on mesomorphic properties was also studied. Compounds with an identical orientation of ester groups in the same direction with respect to the central benzene core exhibited the columnar B1 phase for the shortest length of the terminal chain and the lamellar B2 phase for longer homologues. The reorientation of the ester unit(s) in another series resulted in the appearance of another type of columnar phase (B1REV). [ABSTRACT FROM AUTHOR]

Novel non-symmetrical bent-shaped liquid crystals based on a laterally substituted naphthalene central core and a semifluorinated terminal chain in one arm are presented. The non-substituted (X=H), methyl- (X=CH3) and chloro-substituted compounds (X=Cl) exhibit formation of a B2 phase, the antiferroelectric character of which was proved by electrooptic, dielectric and X-ray studies. In the cyano-substituted materials, the B7 phase appeared. Increasing the length of the polyfluorinated unit leads to an increase of the transition temperatures and broadening of the temperature interval of the B2 and B7 phases, respectively. The length of the perfluorobutyl unit in the terminal chain is sufficient to support the formation of lamellar phases. [ABSTRACT FROM AUTHOR]

In the continuation of our study on heterocyclic mesogens, the structural motif of a 2,5-disubstituted benzothiophene as the central unit was utilised to design novel liquid crystals. Despite the bent molecular structure, the formation of a standard calamitic phase was observed. The mesomorphic properties of the model substances of series I was very close to that of the previously studied 6-substituted derivatives. Introduction of the chiral terminal unit led to appearance of the ferroelectric smectic C* (SmC*) phase in compounds IIa–d. 5-Phenylbenzothiophene based mesogens III exhibited higher clearing temperatures and polymorphism (nematic–smectic A–SmC sequence). Thus, the central benzothiophene unit can be successfully utilised in the design of various liquid crystals. [ABSTRACT FROM AUTHOR]

In this study a new series of bent-core liquid crystals based on laterally substituted 7-hydroxynaphthalene-2-carboxylic acid is presented. All compounds exhibit broken-layer type columnar phases. For CH3 laterally substituted compounds with a longer chain we found a smectic A above a columnar phase on cooling from the isotropic phase. Additionally, for CH3-substituted compounds with the longest chains (C14H29) two switchable columnar phases (B1RevT) occurred below the SmA phase. Two columnar phases were also found for Cl-substituted homologues with the long chain C12H25 and C14H29. For the Cl-substituted materials we found significant lowering of transition temperatures and a very steady columnar phase in a broad temperature interval of up to 130 K. [ABSTRACT FROM AUTHOR]

New non-symmetrical bent-core mesogens with a variable flexible chain length have been synthesised. The compounds were derived from 3-hydroxybenzoic acid, which is the central unit of the molecules. The tails on both ends were connected by ester functionality, one tail contains a terminal double bond and the other is saturated. The compounds represent novel non-symmetric molecules both in their core and tails. The main features of differential scanning calorimetry, polarising optical microscopy, electro-optical and polarisation current measurements for all studied materials indicate a transition between a single tilted synclinic ferroelectric and an antiferroelectric smectic phase. [ABSTRACT FROM AUTHOR]

Several series of new benzofused thieno[3,2‐b]furan‐ and thieno[3,2‐b]thiophene‐based derivatives have been synthesized and their mesomorphic properties investigated. All the studied compounds exhibit a SmC* phase with very wide temperature interval. Additionally, some types of the compounds show the cholesteric, SmA or blue phase. In the ferroelectric SmC* phase we evaluated physical properties of relevance for possible applications. [ABSTRACT FROM AUTHOR]

Novel bent-shaped mesogens based on substituted naphthalene-2,7-diol, possessing a double bond at the end of terminal branches, have been synthesized and characterized. A variety of banana-mesophases has been found, depending on the type of lateral substitution. Increasing the length of the alkyl chain leads to the appearance of the SmC A P A phase for two of the compounds synthesized. Under an electric field a transition into the SmC S P F phase takes place and a tilt angle close to 45° has been found. These materials are appropriate for the preparation of polymeric materials. [ABSTRACT FROM AUTHOR]

Novel series of laterally 1‐substitued (H, Cl, CH 3 , CN, NO 2 ) naphthalene‐2,7‐diol based liquid crystals were synthesized and their mesomorphic properties identified using DSC studies, texture observation, X‐ray investigations and electro‐optical measurements. Depending on the chain length and type of lateral substitution, the compounds exhibit a variety of mesophases. In materials with short alkyl chains, the rectangular columnar B 1 phase was found. Increasing the alkyl chain length for the non‐substituted core causes the appearance of the so‐called B N phase. In CH 3 ‐ and Cl‐substituted compounds, the antiferroelectric B 2 phase (SmC A P A ) was found. Introduction of the CN and NO 2 substituents led to the formation of the B 7 phase. [ABSTRACT FROM AUTHOR]

Two new series of chiral aliphatic and aromatic esters of 7-decyl[1]benzothieno[3,2- b ][1]benzothiophene-2-carboxylic acid were synthesized and their mesomorphic behaviour studied. While the chiral aliphatic esters exhibited only the SmA phase, the antiferroelectric SmC A * phase was found for esters with chiral 4-hydroxybenzoates; for one homologue a ferroelectric SmC* phase was also observed. Introduction of lateral substituents in the 3-position of the 4-hydroxybenzoic acids (methoxy, fluoro, chloro, and bromo) led to a reduction of the polymorphism and only the SmA phase remained. [ABSTRACT FROM AUTHOR]

We present the synthesis and mesomorphic properties of the new series of bent-core liquid crystals based on 3-hydroxybenzoic acid bearing a lateral substituent in the apex position. Four different substituents of various sizes and electronic properties have been used. We have found that only compounds substituted with fluorine are mesogenic and exhibit one mesophase, whose type differs when prolonging the terminal alkyl chain. For homologues with shorter alkyl chains (octyl, decyl), a columnar B1-type of a mesophase was observed, while materials with longer terminal chains (dodecyl, tetradecyl) exhibited a switchable lamellar SmCAPA phase. Calorimetric measurements, texture observations under a polarizing microscope were performed and electro-optical properties studied. Additionally, dielectric measurements were realized to characterize the molecular dynamics in the SmCAPA phase. All mesogenic compounds were further studied by X-ray measurements to confirm phase identification and obtain more information about their structural parameters. [ABSTRACT FROM AUTHOR]

• New liquid crystals. • Photoswitches. • Nematic and smectic mesophase. • Spiropyran-based materials. We present a new type of light responsive self-assembling structures based on a spiropyran photoswitchable unit. The spiropyran central part was modified by functional groups, which enabled the connection of two structurally different elongating parts. Two series of compounds were prepared with reversed orientation of the ester as a linkage group in the molecular core. The properties of the target materials were studied by differential scanning calorimetry and polarized light optical microscopy, which confirmed the presence of a nematic phase for most of the materials. In case of a trifluromethyl-substituted compound, a sequence of nematic – smectic A – smectic C phase was detected and confirmed by X-ray diffraction analysis. The photochromic properties of compounds were studied in solution as well as in mesophases. In the condensed state, UV light-induced switching from the spiropyran form to the merocyanine dye led to isothermal transition from the liquid crystalline phase to the isotropic liquid. [ABSTRACT FROM AUTHOR]

Abstract New type of bent-core molecules based on the 2,5-diphenylthiophene and 3,4-diphenylthiophene central cores have been synthesized as potential liquid crystalline compounds. We have varied non-linear 2,5-diphenylthiophene molecular core as a potential source of central unit of bent-core mesogens and for the first time introduced 3,4-diphenylthiophene central core in the design of V-shaped liquid crystals. Unfortunately, no mesogenicity has been observed for the 3,4-diphenylthiophene-based compounds. The effect of the lateral substitution on the central thiophene in 2,5-diphenylthiophene derivatives has been investigated. We have succeeded in substantial decrease of transition temperatures and the nematic phase has been observed for several compounds. Graphical abstract Unlabelled Image [ABSTRACT FROM AUTHOR]

We present two isomeric series of photosensitive bent-core liquid crystals possessing a lateral chlorine atom in the central resorcinol unit and various linking units in the side arms. With the aim to tune properties of the nematic phase, we have varied the type of the linking unit in the lengthening arm with rising rigidity from benzoate ester, biphenyl, cinnamate, Schiff base to stilbene moieties. In addition to that, we have changed the position of the lateral substituent (chlorine) as well. The mesomorphic properties of the materials have been determined from differential scanning calorimetry, polarizing optical microscopy, dielectric spectroscopy and X-ray studies. We show that synergy of the linking unit with the effect of the lateral substituent gives rise to broad temperature range of mesophases — the nematic phase as well as a SmCP phase. Thanks to the presence of the photosensitive group in the molecular structure, we have been able to transform both mesophases to the isotropic phase under UV light. The chemical structure–mesomorphic properties relationships are discussed with the aid of ab initio calculations and the results presented in context with experimental data. • Two series of 4-chlororesorcinol-based photosensitive bent-core nematogens are presented. • Mutual position of chlorine atom on the central core and the azo group is crucial for mesomorphic behaviour. • Broad stable nematic phase below 100 °C and switchable SmC A P A phase are observed. • Photosensitivity of bulk mesophases is documented by X-ray profile and polarizing microscopy measurements. [ABSTRACT FROM AUTHOR]