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Hybrid Organic‐Inorganic Halide Perovskites (HOIHPs) represent an emerging class of semiconducting materials, widely employed in a variety of optoelectronic applications. Despite their skyrocket growth in the last decade, a detailed understanding on their structure–property relationships is still missing. In this communication, we report two unprecedented perovskite‐like materials based on polyfluorinated imidazolium cations. The two materials show thermotropic liquid crystalline behavior resulting in the emergence of stable mesophases. The manifold intermolecular F ⋅ ⋅ ⋅ F interactions are shown to be meaningful for the stabilization of both the solid‐ and liquid‐crystalline orders of these perovskite‐like materials. Moreover, the structure of the incorporated imidazolium cation was found to tune the properties of the liquid crystalline phase. Collectively, these results may pave the way for the design of a new class of halide perovskite‐based soft materials. [ABSTRACT FROM AUTHOR]

The discovery of a new polar nematic phase; the ferroelectric nematic, has generated a great deal of excitement in the field of liquid crystals. To date there have been around 150 materials reported exhibiting the ferroelectric nematic phase, in general, following three key archetypal structures with these compounds known as RM734, DIO and UUQU‐4N. In this review, the relationship between the molecular structure and the stability of the ferroelectric nematic, NF, phase will be described from a chemist's perspective. This will look to highlight the wide variety of functionalities which have been incorporated into these archetypal structures and how these changes influence the transition temperatures of the mesophases present. The NF phase appears to be stabilised particularly by reducing the length of terminal alkyl chains present and adding fluorines laterally along the length of the molecular backbone. This review will look to introduce the background of the ferroelectric nematic phase before then showing the molecular structures of a range of materials which exhibit the phase, describing their structure–property relationships and therefore giving an up–to–date account of the literature for this fascinating new mesophase. [ABSTRACT FROM AUTHOR]

New Janus-type compounds were synthesised with two different hemispheres structures and properties. The structures contain cyanobiphenyl units linked with 3,4,5-tribenzyloxybenzene or 3,4,5-tridecyloxybenzene units. Also, the influence of the 1,3,4-thiadiazole heterocycle was studied. The mesomorphic properties were studied by differential scanning calorimetry, polarised light optical microscopy and thermal gravimetric analysis. The mesophases obtained depend on the structure of the hemispheres, even obtaining mesophases different from the initial ones. The new materials synthesised presented photoluminescent properties, which were studied in solution. [ABSTRACT FROM AUTHOR]

Liquid crystals are self-organized anisotropic fluids which exhibit ordered states ranging from nematics to smectics/hexatics. Hybridized liquid crystals with nanoparticles broaden the research area in finding the novel functional devices. Reported herein, the study of highly stable room temperature nematic liquid crystal E7 and carbon-coated cobalt (Co) nanoparticles. Dispersion of 0.50 wt.% Co into E7 has been introduced to tailor the physical parameters of host E7. Dielectric studies have been performed in planar as well as homeotropic cells in the frequency range of 20 Hz–10MHz while photoluminescence spectra have been recorded at excitation wavelength of 325 nm in planar cells. Dielectric studies reveal the change in phase transition temperature and molecular dynamics associated with magnetic nanoparticles doped liquid crystals. Quenching in photoluminescence intensity has been observed with the inclusion of Co nanoparticles due to the formation of non-radiative channels in the composite system. The intercalation of Co nanoparticles into E7 studies manifests the strong correlation between liquid crystals and nanoparticles. Allocation of magnetic attributes onto liquid crystal molecules finds potential applications in advanced magnetic materials, information devices and optical devices. [ABSTRACT FROM AUTHOR]

We study the nature of the nematic to smectic-A phase transition under confinement conditions in the context of Landau-de Gennes theory. The effect of quenched disorder on the nematic to smectic-A transition temperature, order parameter, enthalpy, and thermal hysteresis are discussed followed by phase diagrams. The tricritical behavior of the nematic to smectic-A phase under confinement conditions is predicted. [ABSTRACT FROM AUTHOR]

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A series of azobenzene liquid crystals containing one amino acid residue were synthesized. They exhibit smectic mesophases. The compounds derived from alanine can self-assemble into twisted nanoribbons. The molecules organized in a monolayer structure within the nanoribbon. Circular dichroism characterization indicated that the neighboring liquid crystal cores packed in a chiral structure. FT-IR spectra indicated that the nanoribbons were caused by H-bonding and association of hydrocarbon chains. [ABSTRACT FROM AUTHOR]

Pillar[5]arene (P5A) mesogens were synthesized by decorating the central P5A core with ten benzylether dendron via click reaction. Each benzylether dendron was terminated with multialkoxy chains. Such P5A mesogens can self-assemble into liquid crystal (LC) phases with layer structure (Smectic A phase) and tubular structure (Colhex/p6mm phase). Molecular packing models for these mesophases were initially established. Additionally, such P5A mesogens can act as chemo-sensor to recognize Fe3+ and Cu2+. The influence of the number of terminal alkoxy chain on the self-assembly and chemo-sensor properties of these P5A derivatives were investigated. [ABSTRACT FROM AUTHOR]

Two series of acrylate liquid crystals with enantiotropic SmA and SmC phases were synthesised. With increasing the alkoxy chain length, SmC phase was favourable to be formed. The mesophases were confirmed by taking small angle X-ray scattering patterns. Moreover, a diacrylate liquid crystal with an enantiotropic SmA phase was synthesised. Smectic liquid crystal mixtures were prepared using the diacrylate liquid crystal (or a mixture of an acrylate liquid crystal and the diacrylate one) and a dichroic dye. After photopolymerisation at the SmA phase, polymeric polarisers were obtained. The degree of polarisation was increased with increasing the dye concentration and film thickness. [ABSTRACT FROM AUTHOR]

Magnetoelectric (ME) materials exhibiting coupled electric and magnetic properties are of significant interest because of their potential use in memory storage devices, new sensors, or low‐consumption devices. Herein, we report a new category of ME material that shows liquid crystal (LC), ferroelectric (FE), and field‐induced single molecule magnet (SMM) behaviors. Co(II) complex incorporating alkyl chains of type [Co(3C16‐bzimpy)2](BF4)2 (1; 3C16‐bzimpy=2,2'‐(4‐hexadecyloxy‐2,6‐diyl)bis(1‐hexadecyl‐1H‐benzo[d]imidazole)) displayed a chiral smectic C mesophase in the temperature range 321 K–458 K, in which distinct FE behavior was observed, with a remnant polarization (88.3 nC cm−2). Complex 1 also exhibited field‐induced slow magnetic relaxation behavior that reflects the large magnetic anisotropy of the Co(II) center. Furthermore, the dielectric property of 1 was able to be tuned by an external magnetic field occurring from both spin‐lattice coupling and molecular orientational variation. Clearly, this multifunctional compound, combining LC, FE, and SMM properties, represents an entry to the development of a range of next‐generation ME materials. [ABSTRACT FROM AUTHOR]

Bent-core liquid crystal (LC) is used to dope the (4-cyano-4′-pentylbiphenyl) liquid crystal (5CB). The polarizing microscopy results show that 5CB and LC exhibit Nematic (N) and Banana-Shaped (B1) mesophases, respectively. In this paper, we use dielectric spectroscopy to determine the dielectric properties of the 1% LC doped with 5CB liquid crystal. The dielectric parameters of these materials have been determined by different applied voltage. In this respect, dielectric properties of 5CB + 1% LC have been compared with 5CB. The dielectrical anisotropy of 5CB and 5CB + 1% LC liquid crystal composite changes from the positive dielectric anisotropy to negative with the frequency of the applied voltage. The critical frequency fc values of dielectrical anisotropy for 5CB and 5CB + 1% LC composite were found to be 688 and 534 kHz, respectively. The real (ε′) and imaginary components (ε′′) of dielectric constant have been calculated by capacitance method. It has been also determined that adding LC to 5CB decreases the voltage dependent dielectric strength and increases threshold voltages. [ABSTRACT FROM AUTHOR]

A new series of polysiloxane glassy cholesteric liquid crystal copolymers with menthyl- and cholesteryl-based mesogenic units in the side chains, denoted as P-MtxChy (x, y expresses the molar ratio of monomers Mt and Ch in copolymeric synthesis, and x + y = 7.) were successfully synthesised by hydrosilylation reaction. The mesomorphic properties and phase behaviours were studied by differential scanning calorimetry (DSC), polarising optical microscopy (POM) and X-ray diffraction. Optical properties were investigated by the UV-VIS spectrum. Using the volume-excluding action of mesogenic units in side chains, we obtained glassy cholesteric liquid crystal copolymers. By varying molar ratio of Mt and Ch in copolymers, the helical pitch was adjusted into visible light region. With the increase of Mt, the maximum reflection wavelength off normal 8 ° shifted from 548 nm of P-Mt3Ch4 to 650 nm of P-Mt4Ch3 to 872 nm of P-Mt5Ch2, and the reflected colours changed from green to red. These well-oriented glassy films have shown good morphological stability below the glass-transition temperature (Tg) for more than a year. [ABSTRACT FROM AUTHOR]

We revisited the nematic-isotropic (NI) transition of the Lebwohl-Lasher lattice model with a detailed investigation of samples containing 200 x 200 x 200 particles. The large-scale Monte Carlo (MC) simulations involved were carried out following the standard Metropolis, as well as the cluster MC Wolff algorithms. A notable free-energy barrier was observed between the isotropic and nematic phase, leading to long-lived metastable states and hysteresis. We provide an improved estimate of the nematic-isotropic transition temperature TNI, of the supercooling and superheating temperatures, of the temperature of divergence of pretransitional effects TC* as well as an analysis of the size distribution of the ordered domains above TNI, contributing to a better understanding of this transition of key importance for liquid crystals. This article is part of the theme issue 'Topics in mathematical design of complex materials'. [ABSTRACT FROM AUTHOR]

The biaxial nematic ( N B ) phase bordered by two uniaxial nematic (discotic – N D and calamitic – N C ) phases and the one between N D phases are studied in potassium laurate (KL), decanol (DeOH) and D 2 O mixture using conoscopic images. The sequences of phases ( N D → N B + → N B − → N C and N D → N B + → N D ) were optically characterized, where N B + and N B − are the biaxial positive and biaxial negative nematic phases, respectively. A new sequence of phases ( N D → N B + → N B − → N B + → N D ) found in one line of the phase diagram positioned close to the interface with the N C phase was also optically confirmed through conoscopic images. The N B + (N B −) → N B − (N B +) transition point was determined by means of image processing. In this review work, we emphasize the relevance of the optical characterization of an N B − phase inherent to the nature of this lyotropic material. [ABSTRACT FROM AUTHOR]

In this paper, novel chiral calamitic compounds, consisting of n-dodecyloxyphenyl substituted pyridine carboxylate core linked to one or two benzene rings through ester linkers have been synthesised by multi-step procedures. The other end has been varied by introducing a flexible (S)-2-methylbutyloxy or (S)-3,7-dimethyloctyloxy chiral chain. The liquid crystal properties of new compounds were investigated by various experimental techniques such as DSC, POM and SAXS. The pyridine-based calamitic compounds exhibited enantiotropic chiral smectic mesophases such as SmC*, SmA or uncharacteristic mesophase depending on hetero aromatic rings such as nicotinate or picolinate cores, number of aromatic rings and the type of chiral-branched chain. [ABSTRACT FROM AUTHOR]

Compared to other photochromophores that show E-Z isomerisation, acylhydrazones are still relatively little explored in the field of liquid crystalline materials. To improve the knowledge about this group and their viability as the mesogenic core, herein a series of 10 molecules were synthesised and had their thermal and photoisomerisation properties investigated and correlated to structural changes. Mesomorphism was investigated by POM, DSC, XRD and SAXS techniques (using synchrotron radiation), while photoisomerisation was accompanied by UV-Vis absorption spectroscopy and 1H NMR measurements. It is demonstrated that the higher the alkoxy chain number, the lower the transition temperatures and the greater the propensity for a columnar arrangement, so that the hexacatenar compounds maintained a Colh mesophase at room temperature. On the other hand, a SmC phase was stabilised for low alkoxy chain number and the mesomorphism was extinguished for the non-symmetric structures. All compounds successfully presented E-Z photoisomerisation in solution, being faster for the molecules with the mesogenic core expanded by the addition of a benzoate unit. Overall, this work demonstrates the viability and effectiveness of the use of acylhydrazones in photoisomerizable liquid crystals, showing the advantages compared to other groups and opening an important path for applications based on this photochromophor. [ABSTRACT FROM AUTHOR]

In this paper, new liquid crystal compounds with negative dielectric anisotropy were synthesised by regulating the substituents on the benzofuran ring. Their structures were confirmed by 1H-nuclear magnetic resonance, 13CNMR and mass spectra. The effects of substituent on the properties of liquid crystals were investigated. Compared with the reference compounds, the compounds with 5-ethoxy-6,7-difluorobenzofuran ring exhibit higher clearing points as well as the tendency of expansion of SmA phase range. The density functional theory calculation results reveal that the 6-ethoxy-7-fluorobenzofuran-based compound has smaller aspect ratio than that of the 5-ethoxy-6,7-difluorobenzofuran-based compound, which results in the diminish of the mesophase. Although the dielectric anisotropy of the 5-ethoxy-6,7-difluorobenzofuran-based compound is slightly lower than that of the reference compound, it has both the largest perpendicular and parallel dielectric constant. [ABSTRACT FROM AUTHOR]

We report on the temperature-dependent measurements of dielectric permittivity, birefringence, elastic constants and rotational viscosity for 4-propoxy-biphenyl-4-carbonitrile in the nematic region. The temperature dependence of the three elastic constants was determined from studies of the Freédericksz transition. The thermal dependence of elastic constants shows features similar to the literature (bend > splay > twist). Elastic constants are proportional to the square of the order parameter. Temperature-dependent dielectric characterisation was carried out at a frequency of 10 kHz. The compound shows positive dielectric anisotropy in the nematic phase. The rotational viscosity is found to be relatively low. Temperature dependence of order parameter is estimated using Haller's method. The figure of merit was also calculated as a function of temperature. [ABSTRACT FROM AUTHOR]

Refractive index measurements and conoscopic images has confirmed the occurrence of biaxial negative ( N B − ) and biaxial positive ( N B + ) nematic phases between the two uniaxial nematic (calamitic − N C and discotic − N D ) phases. These nematic phases are found in a phase diagram line of potassium laurate (KL), decanol ( D e O H) , potassium sulfate and water. Biaxial positive ( N B +) nematic phase is also optically characterized between two uniaxial N D phases in a KL, DeOH, and D 2 O mixture. Temperature dependence of the angles ( 2 V X and 2 V Z ) between two optic axes of ( N B − and N B + ) phases is obtained from refractive index data. The transition point ( N B − − N B +) characterized by an angle peak corresponds to the change in the biaxial configuration of the optical axes and optical signal of the biaxial nematic phase. The micellar configuration of biaxial nematic phases is discussed as a consequence of our experimental data. [ABSTRACT FROM AUTHOR]

Two series of 4,6-diamino-1,3,5-triazine triblock polyphiles consisting of an extremely long bisthiophene/triazole based rigid cores, with flexible alkyl chains at one end and a polar 4,6-diamino-1,3,5-triazine at the other end were synthesized. Col hex / p 6 mm mesophases were displayed by all bisthiophene based 4,6-diamino-1,3,5-triazine derivatives, whereas both Col hex / p 6 mm and Cub I / Pm 3 ¯ n mesophases could be formed by corresponding triazole based 4,6-diamino-1,3,5-triazine derivatives. Evidence for the formation of the extra H-bonding between central triazole units and terminal 4,6-diaminotriazine groups which was responsible for the formation of cubic phases in triazole based compounds was obtained based on FT-IR measurements. Additionally, these triblock polyphiles can form organogels with interesting morphologies in different solvents. The influence of the alkyl chain length and the polarities of the heterocycles (bisthiophene/triazole) on the self-assembly of these compounds was systematically studied. Finally, these triblock polyphiles showed dual selectivities towards Pb2+ and Fe3+ ions. Image 1 • Bisthiophene/triazole diamino triazine triblock polyphiles have been synthesized. • They display Col hex / p 6 mm and Cub I / Pm 3 ¯ n mesophases despite their long rigid cores. • These compounds can form organogels in organic solvents with different morphologies. • These compounds can act as chemosensor of metal ions. [ABSTRACT FROM AUTHOR]

Based on a thermodynamic model, we investigate how the density variation influences the smectic (Sm A)–isotropic (I) phase transition. We find that the density variation shifts the smectic A–isotropic transition temperature, however, first-order nature of the transition remains the same. Here, we also examine the effect of high pressure on the thermodynamic quantities. The present analysis shows that the pressure strongly influences the enthalpy and density step at the clearing transition. The pressure dependence of the thermodynamic properties is incorporated through the pressure dependent second Landau coefficient and the coefficients which couple the nematic and smectic order parameters to the density. We find a close agreement between theoretical and experimental results. Furthermore, we discuss the implications of the results for achiral liquid crystals. [ABSTRACT FROM AUTHOR]

Abstract In this study, the dielectric properties of the liquid crystal 4–(7,7,8,8,9,9,10,10,10–nonafluorodecyloxy)biphenyl–4′–carboxylic acid (NBCA) exhibiting a Smectic C mesophase have been analyzed. NBCA has two critical temperatures which are 194 °C for the crystal phase to the smectic phase transition, and 269 °C for the smectic phase to the isotropic phase transition. Impedance spectroscopy measurements were made at regular intervals at different temperatures which includes these transitions. By using capacitance method, the complex dielectric constants have been calculated for each temperature, and the real part of dielectric constants have been fitted to the Cole-Cole equation. In addition, ac conductivity mechanisms of the NBCA at different temperatures and different phases and also activation energies which belongs to some selected frequencies have been determined by the imaginary part of dielectric constants. Highlights • The dielectric properties of the liquid crystal NBCA have been analyzed. • The transition temperatures were verified by dielectric measurements of the NBCA. • The conductivity mechanisms for different temperatures have been determined. • The activation energies for selected angular frequencies have also been calculated. • This characterization of NBCA can be beneficial for liquid crystal applications. [ABSTRACT FROM AUTHOR]

Copper(II) benzoates (n OBA-Cu) with various terminal alkoxy carbon numbers, n = 7 –12, were prepared from p - n -alkoxy benzoic acids (nOBAs). Fourier transform infrared (IR) experiments suggested that dimerization through copper(II) chelating bidentate coordination created n OBA-Cu with a linear rod-like structure, similar to the hydrogen-bonded structure of its parent n OBA. However, the coordination structure of n OBA-Cu changed during heating. Periodic density functional theory calculations provided valuable insight into the possible arrangement of the parent and copper(II)-coordinated n OBAs. The formation of binuclear complexes between two adjacent n OBA-Cu dimers forced n OBA-Cu to arrange itself in a layer and exhibit smectic A mesophase. Accordingly, four types of IR stretching absorption of benzoyl carbonyl were observed in binuclear n OBA-Cu complexes, replacing the original symmetric and asymmetric vibrations of benzoyl carboxylate in chelating bidentate coordination. The lateral association by π – π interactions between adjacent parent n OBA dimers preferred a progressive smectic C arrangement. The origin of the odd–even effect was understood from the consideration of the molecular structure. One-dimensional periodic calculations help explore smectic mesophases. Binuclear Cu(II) structure forces a layer arrangement of copper(II) benzoates. An odd–even effect was understood from the consideration of molecular arrangement. [ABSTRACT FROM AUTHOR]

Owing to their dynamic attributes, non‐covalent supramolecular interactions have enabled a new paradigm in the design and fabrication of multifunctional material systems with programmable properties, performances, and reconfigurable traits. Recently, the "halogen bond" has become an enticing supramolecular synthetic tool that displays a plethora of promising and advantageous characteristics. Consequently, this versatile and dynamic non‐covalent interaction has been extensively harnessed in various fields such as crystal engineering, self‐assembly, materials science, polymer chemistry, biochemistry, medicinal chemistry and nanotechnology. In recent years, halogen bonding has emerged as a tunable supramolecular synthetic tool in the design of functional liquid‐crystalline materials with adjustable phases and properties. In this Concept article, the use of halogen bond in the field of stimuli‐responsive smart soft materials, that is, liquid crystals is discussed. The design, synthesis and characterization of molecular and macromolecular liquid crystalline materials are described and the modulation of their properties has been emphasized. The power of halogen bonding in offering a large variety of functional liquid crystalline materials from readily accessible mesomorphic and non‐mesomorphic complementary building blocks is highlighted. The article concludes with a perspective on the challenges and opportunities in this emerging endeavor towards the realization of enabling and elegant dynamic functional materials. Holy halogens: The halogen bond is increasingly used in the realization of advanced functional materials. In this Concept article, we discuss the usage of halogen bond as an enabling supramolecular tool in the preparation of different kinds of functional liquid crystalline materials towards the understanding of their structure–property and structure–function relationships. [ABSTRACT FROM AUTHOR]

Abstract The synthesis of a series of symmetrical liquid crystals having naphthalene as the central rigid core and attached to long chain flexible 4′-alkoxybenzoate moiety at positions 2,6 - of the aromatic ring are reported. The mesophase behavior of the molecules was investigated using differential scanning calorimetry (DSC), polarizing optical microscopy (POM) and X-ray diffraction studies. The studies reveal that the synthesized compounds exhibit stable enantiotropic mesophase of Smectic A (SmA) and Nematic (N) phase. The mesophase appearance is independent of the length of the alkyl chain. The molecular structure was determined by single crystal X-ray diffraction technique. The derivative with n- heptyloxy- flexible chain crystallizes under triclinic, P 1 ¯ space group with unit cell dimension a = 5.569(3) Å, b = 10.540(5) Å, c = 15.254(9) Å, α = 73.434(18)o, β = 80.807(19)o and γ = 82.02(2)o, V = 843.1(8) Å3. The dihedral angle between the naphthalene ring system and the benzoate moiety is 63.63(2)o. Graphical abstract Image Highlights • We have synthesized symmetric naphthalene centered molecules. • All the molecules were characterized by UV, IR, NMR analysis. • Liquid crystal property was evaluated by DSC and POM techniques. • Single crystal structure was confirmed by X-ray analysis. [ABSTRACT FROM AUTHOR]

Abstract Melt-crystallization of poly(butylene 2,6-naphthalate) (PBN) at temperatures lower than about 160 °C follows Ostwald's rule of stages via intermediate formation of a smectic liquid crystalline phase (LC-phase). The transient LC-phase has been isolated by interruption of the isothermal crystallization process at 140 °C at sub-second timescale, and then its disordering was analyzed on heating at a rate of 2000 K/s, which suppresses the transition into α-crystals. The disordering temperature of the LC-mesophase is slightly lower than 200 °C, and as such 20–30 K lower than the melting temperature of α-crystals formed from the LC-phase at 140 °C. Analysis of the bulk enthalpy of formation of the LC-phase revealed that it covers only 20–25% of the total bulk enthalpy of crystallization, which is considered further proof of its smectic nature. Graphical abstract Image 1 Highlights • Crystallization of PBN below 160 °C follows Ostwald's rule of stages. • Crystallization below 160 °C proceeds via formation of a liquid crystalline (LC) phase. • Disordering of the LC-phase was analyzed on fast heating, suppressing the transition into crystals. • Disordering of the LC-phase occurs 20–30 K lower than melting of α -crystals. • The bulk enthalpy of LC-phase formation is about 20–25 % of that of crystallization. [ABSTRACT FROM AUTHOR]

A novel azoester homologous series with chloro lateral group and a fluoro terminal end group was synthesized and characterized for mesomorphic properties. It consists of thirteen azo ester derivatives from trans-4-n-alkoxy cinnamic acid with 4-hydroxy-3-chloro phenyl azo-3-chloro-4-fluoro benzene. Mesomorphic property commences from C4homologue as smectic.C1 to C3 member of the series are non-mesomorphic. C4 to C18 homologous are enantiotropic smectic A phase. The nematic mesophase is totally absent. Texture and transition temperatures of the homologues are determined by an optical polarizing microscopy equipped with heating stage. 1H NMR, IR spectra, mass spectra, of some member is included. The spectroscopic analysis supports the molecular structure. A phase diagram is used to illustrate the mesomorphic behaviour across the series. Mesophaselength for smectic is varying from18.0°C to 69.00C. Mesomorphic properties of the novel azoester series are compared with structurally similar series. [ABSTRACT FROM AUTHOR]

The synthesis and mesophase characterization of two 2,6-bis(4-(alkyloxy)phenyl)dithieno [3,2-b:2′,2′-d]thiophenes indicate successful application of a palladium-catalyzed carbon-sulfur cross-coupling/5-endo-dig cyclization sequence and the appearance of a nematic mesophase in the resulting products. Spectroscopic and cyclovoltammetric measurements reveal molecular orbital energies that are comparable to a good standard hole conductor. Consequently, one of the compounds was successfully applied as a hole conducting layer in an electroluminescent sample. In thin-film transistors (TFT), the two compounds show charge carrier mobilities in the saturation region μ sat of 0.13 cm 2 V −1 s −1 and 0.03 cm 2 V −1 s −1 , respectively. The injection barrier at the metal semiconductor interface could be reduced by alkanethiol treatment, thereby enabling a linear I D (V D ) characteristics in the low V D region and maximum currents up to I D,max  = - 18 μA at V G  = - 2.5 V in the saturation regime. Inverter circuits in single-type TFT technology were implemented. [ABSTRACT FROM AUTHOR]

An amphiphilic liquid crystal (LC) block copolymer based on aliphatic polycarbonate with pendant cholesteryl groups was synthesized by the coupling reaction. The structure and LC properties of the obtained block copolymer were characterized using FT-IR, 1 H NMR, DSC, POM and XRD. The results showed the copolymer exhibited broken focal conic texture and fan-shaped texture of a smectic A phase during the heating and cooling process. Moreover, this copolymer showed mesophase state below body temperature, and it would be promising candidate as self-assembly material for applications in drug delivery. In addition, the self-assembly, drug loading and release behavior of the LC copolymer were investigated with UV–vis, DLS and SEM. It was found that the initial copolymer concentration and the pH value had a critical influence on the self-assembly behavior and the particle size of the micelles. What's more, the drug release also presented a pH response and the drug-loaded copolymer micelles were stable. [ABSTRACT FROM AUTHOR]

Abstract: A novel type of discotic polycyclic aromatic hydrocarbon (PAH) based on an enlarged dibenzo[a,c]phenazine core has been developed. The large conjugated mesogenic core with increased dipole moment derived from S,N heteroatoms facilitates the formation of highly ordered columnar superstructures both in solution and bulk. Columnar mesophases, including liquid crystal (LC) and plastic crystal (PC) assemblies could form unprecedentedly based on the same PAH core. The cores are delicately modulated by the peripherical alkoxy chains. Both mesogens have mechanochromic fluorescent (MCF) character, which is also structure dependent and correlated with the different mesophase formation. For the first time, MCF properties can be realized in such a large conjugated mesogenic system. [ABSTRACT FROM AUTHOR]

A group of new mesomorphic compounds with cholesterol-based, which have derivative of the cinnamic acid, with different lengths of terminal alkoxy chains, are synthesized and characterized. The mesomorphic properties were investigated by DSC and POM. All target compounds showed a cholesteric phase. For 12-TC and 14-TC besides a cholesteric phase, also revealed a SmA* phase. The experimental results demonstrated that with the increase in the terminal chain lengths, the thermal stability of the smectic mesophases of these liquid crystals was increased, and these compounds shows brilliant color changes in the temperature ranges of cholesteric phase. [ABSTRACT FROM AUTHOR]

The combination of aggregation-induced emission (AIE) and liquid crystal properties generates solid-state efficient luminescent liquid crystal materials. Here in, we reported the synthesis of 1,3,5-triazine-2,4,6-tricarboxamide and utilized it as a supramolecular organic motif for the AIE-active liquid crystal material. The compound exhibits high-intensity emission maxima at 417 and 468 nm in the solid state with excitation at 254 nm, whereas it shows weak emission in the solution phase. Also, this compound behaves as liquid crystalline material and shows columnar hexagonal mesophase with endothermic peaks at 73.4°C, 185.6°C, and exothermic peaks were observed at 181. 9°C and 66.1°C with focal conic fan shape texture. The thermal data showed that the compound is stable up to 200°C. [ABSTRACT FROM AUTHOR]

Small-angle X-ray scattering (SAXS) experiments and molecular dynamic modelling of the mesomorphic organisation of hexa-n-pentoxy-2,3,6,7,10,11-triphenylene are reported. Simulated SAXS patterns extracted from molecular dynamic simulations account for the fact that despite a perfect organisation of the columns in a 2D hexagonal array, in most case, SAXS patterns show only the fundamental diffraction peak with a limited number of higher order reflections. [ABSTRACT FROM AUTHOR]

Two sets of new ethyl 7-hydroxycoumarin-3-carboxylate derivatives were synthesized and characterized to study the liquid crystalline properties. Chemical structures were confirmed by IR, NMR, CHN analysis techniques. Mesomarphic properties were accomplished by DSC, POM and X-ray studies. Density functional theory calculations and photophysical studies also performed. In the first set, smaller homologues of alkoxybenzoic acid derivatives exhibit monotropic smectic A (SmA) and higher homologous exhibit enantiotropic smectic A mesophase. The second set alkyl biphenyl derivatives exhibit stable SmA and nematic (N) mesophases. The well defined focal conic texture for SmA and threaded texture for nematic mesophases have been observed. [ABSTRACT FROM AUTHOR]

We performed photo-current experiments on various liquid crystal (LC) cells, and compared with the results of conventional evaluations of reliability of LC display (LCD) such as voltage holding ratio (VHR), ion density, and flicker. The accumulated charges in LC cells were estimated by the time integration of photo-currents. Good correlations among observed photo-current, estimated charges, and flicker drift were obtained, which revealed that the accumulated charges in LC cells are one of the major factors to cause the flicker drift. [ABSTRACT FROM AUTHOR]

Two homologous series of mesogenic Schiff-bases, [4-(((4-(1,3-dioxoisoindolin-2-yl)phenyl)imino)methyl)-3-hydroxyphenyl-4-(alkoxy)benzoate, HL 1 n , (Series I), which is an ester derivative of HL and 2-(4-((4-(alkoxy)-2-hydroxybenzylidene)amino)phenyl)isoindoline-1,3-dione, HL 2 n , (Series II), which is an alkoxy derivative of HL where HL = 2-{4-[(2-Hydroxy-benzylidene)-amino]-phenyl}-isoindole-1,3-dione) and n = C 8 H 17 , C 10 H 21 , C 12 H 25 and C 14 H 29 ] have been prepared and their molecular structures and thermal behaviour studied by FTIR, NMR and ESI-MS spectrometry, DSC, POM and variable temperature PXRD techniques; all these derivatives displayed an enantiotropic liquid crystalline behaviour with Nematic texture while few of them also exhibited SmA phase. Influence on thermal behaviour and mesomorphic properties upon changing the spacer was investigated in both the series. The HOMO and LUMO band gaps were found to be 2.89 and 3.26 eV for the two series respectively which were found to be in reasonable agreement with theoretical calculations (by DFT) made on optimized structure of one representative compound of each series. [ABSTRACT FROM AUTHOR]

A series of symmetrical chiral, liquid crystal dimeric molecules possessing ester- linked, biphenyl-naphthyl cores with varied spacer lengths and terminal vinyl groups have been synthesized using Naproxen as the synthetic precursor. The synthesized symmetrical chiral dimers were characterized by 1H NMR spectroscopy, and their liquid crystalline behavior was confirmed by DSC and HOPM studies. Structural effects on the mesomorphic and physicochemical properties were investigated in terms of variation of chiral chain length. The synthesized dimeric compounds exhibited SmX*, SmC*, SmA*, N*, BPI*, and BPII*mesophase sequences. An odd-even effect was observed in the dimers and the duration of the mesophase decreased with increasing spacer length. The synthesized vinyl substituted liquid crystalline dimers are particularly useful in understanding liquid crystal polymorphism and act as model compounds for liquid crystal polymers. [ABSTRACT FROM PUBLISHER]

In this study, the synthesis, structural characterization and mesomorphic properties of newly thirteen calamitic rod-shaped compounds derived from chalcone and 4-n-alkoxy benzoic acid. Here we present, chalcone as central group and terminal side substituted iodo (−I) group containing homologous series. Comp.C1displayed nonmesogenic nature, while comp.C3to comp.C18shows enantiotropic smectic plus nematic property except comp.C2which show only nematic phase. It is shown that chalcone as central linking unit favors a calamitic liquid crystalline behaviour in molecules. Phase transition temperatures of present synthesised compounds were determined by optical polarising microscopy (POM), differential scanning calorimetric (DSC). Thermal stabilities for smectic and nematic mesophases are 150.18 and 163.58 respectively. [ABSTRACT FROM PUBLISHER]

A new side cholesterol-functionalised liquid crystal (LC) copolymer based on aliphatic polycarbonate backbone was synthesised. The chemical structures of the block copolymers obtained in this study were characterised with Fourier Transform Infrared Spectroscopy (FT-IR) and Proton Nuclear Magnetic Resonance (1H NMR) spectra. Their thermal stability and phase behaviours were investigated with thermogravimetric analysis (TGA) measurements, differential scanning calorimetry, and polarising optical microscopy. The molecular organisation in the mesophase was studied by temperature-dependent X-ray diffraction (XRD). As a result, the block copolymer bearing side cholesteryl groups showed a glass transition at 15.8°C and a smectic A (SmA) to isotropic phase transition at 151.3°C on heating cycle. XRD indicated that the block LC copolymer showed an interdigitated molecular arrangement of the mesogenic units within the smectic layers. This partial bilayer structure was similar to the SmA phase formed by polar mesogens. [ABSTRACT FROM AUTHOR]

This study presents the synthesis and mesomorphic properties of a series of biphenyl benzoate liquid crystals carrying a perfluorinated segment, via three uncommon flexible linkers. In particular, a ( E )-2-propenyloxy linker was used which was issued from an elegant regioselective dehydrohalogenation reaction. The remarkable microsegregation effect of the perfluorinated segment, led to the formation of highly stable untilted smectic mesophases. For all mesophases, the molecular packing corresponds to a monolayer arrangement of the mesogenic parts and a partial intercalation of the perfluorinated chains, measured by a intercalation ratio parameter τ F . Geometrical calculations based on Xrays data led to τ F comprised between 1.48 and 1.68 depending of the mesophase and temperature. [ABSTRACT FROM AUTHOR]

The results of high-resolution x-ray reflectivity study of nano-dimensionally thin arsenic trisulfide (As2S3) glass films reveal surface roughness anisotropy upon prolonged irradiation with polarized 436 nm blue light. The anisotropy correlates with the photoinduced anisotropy and LC photoalignment observed on these thin films. However, the As2S3film's thickness reduces drastically during the reflectivity experiments, and ambient oxygen and moisture penetrate the film and create a second altered thin layer on top of a thicker film of As2S3. The results confirm the viability of As2S3films for non-contact LC photoalignment material but suggests the need for further process optimization to reduce the films' degeneration to increase their effectiveness. [ABSTRACT FROM AUTHOR]

Structure of an oriented layer of mesogens on the interface at the isotropic phase (IP) – nematic liquid crystal (NLC) transition has been studied by polarization microscopy method. The thickness of the oriented layer was found to be equal to 50 ÷1000 µm, it decreases with a reduction of the surface curvature radius. Analytical expressions for the phase delay difference arising at passing of plane-polarized light through the mesogen layer oriented towards cylindrical and spherical surfaces have been obtained. The order parameter in mesogens at the IP-NLC transition was determined. [ABSTRACT FROM AUTHOR]

In this article, we report on the liquid-crystalline properties of the 4-ω-alkenyloxy-4′-cyanobiphenyl series of compounds up to a total aliphatic chain length of eleven. When compared to the analogous fully saturated compounds, we find that the smectic layer spacing is significantly larger for the alkene-terminated materials; conversely the dielectric anisotropy in the nematic phase was found to be significantly smaller. The ability to manipulate bulk properties of nematic and smectic mesophases may have future relevance for display applications. [ABSTRACT FROM AUTHOR]

Five types of new pyridine-based azo compounds, namely, 4-(4′-pyridylazo)-4′‘-alkoxybenzoates or 4-(4′-pyridylazo)-4′’-substituted benzoates with straight or branch terminal were prepared as hydrogen bond (H-bond) acceptors to build mesogens. After self-assembled with different carboxylic acids, the resulted H-bond complexes were confirmed for the stability of H bond by fourier transform infrared spectroscopy (FTIR) spectroscopy, and investigated for the mesophase behaviour by differential scanning calorimetry and polarised optical microscopy. The influence of terminal chains in azo accepter or acid donor and the structure of acid donors on the mesogenic behaviour were discussed in detail. [ABSTRACT FROM AUTHOR]

The influence of the terminal side chain and lateral nitro on mesomorphism due to the flexibility and polarity of lateral group is investigated. A new homologues series is synthesized to accomplish this aim. The C1to C3homologue are nonmesomorphic, while the rest of the homologues exhibit enantiotropic nematic and smectic properties. The texture of the nematic mesophase is of threaded, Schlieren and droplets type. All these compounds were characterized by elemental analyses and spectroscopic techniques of FTIR and1H Nuclear magnetic resonance (NMR). The phase behaviour was studied by polarizing optical microscopy (POM), differential scanning calorimetry (DSC), and X-ray diffraction techniques. [ABSTRACT FROM PUBLISHER]

Due to the importance of liquid crystals in modern technology and food industry, understanding their structural and dynamical properties are scientifically important. In this study, we applied extensive molecular dynamics simulations to infer the effect of the molecular elongation on the formation, stability and dynamics of liquid crystal mesophases in a system of Gay-Berne model mesogens with parameters GB (k , k ′ = 20 , μ = 1 , ν = 1). Four aspect ratio values, k = 2 , 3 , 4.4 and 5 , were studied at pressure P * = 4. Thermodynamics properties, the order parameter and pair distribution functions (both translational and positional), helped to identify phases, hysteresis, and consequently phase diagrams. By increasing aspect ratio from 2 to 5 , nematic and smectic phases were induced and all transition temperatures were shifted to higher values, hence, the range of stability of the nematic and smectic mesophases became wider. The analysis of the coordination numbers and angular distribution functions showed that the structure of the solid phase of system with k = 2 at lowest temperatures was fcc which by increasing the aspect ratio changed to a complete hexagonal in-layer structure. Moreover, by increasing the axial ratio of particles, decoupling between the principal components of diffusion coefficients increased, where it reflects an increase in the molecular orientational order in the system with higher k. The effect of increasing aspect ratio was more pronounced on inter-layers diffusion rather than the in-layers. In all mesophases parallel components of diffusion coefficients were greater than the perpendicular components. We analyzed the results based on the existing theoretical descriptions and experimental observations. • For elongations k = 3 , 4.4 a n d 5 , in all mesophases, D ∥ * > D ⊥ *. • The effect of increasing k was more pronounced on parallel diffusion than on perpendicular one. • By increasing the aspect ratio and pressure, the range of stability of each mesophase expanded over a wider temperature interval. • The results of this work are commonly observed in experiments on real thermotropic liquid. • The Chu and Moroi model better described the diffusion coefficients than the Hess-Frenkel-Allen model. [ABSTRACT FROM AUTHOR]

A highly sensitive cholic acid biosensor based on 4-cyano-4′-penthlbiphenyl (5CB) Liquid crystal droplets in phosphate buffer saline solution was reported. A radial-to-bipolar transition of 5CB droplet would be triggered during competitive reaction of CA at the sodium dodecyl sulfate surfactant-laden 5CB droplet surface. Our liquid crystal droplet sensor is a low-cost, simple and fast method for CA detection. The detection limit (5 μM) of our method is 2.4 times lower than previously report by using liquid crystal film to detection of CA. [ABSTRACT FROM AUTHOR]

A new series of tolane-based liquid crystals with different five-membered N-heterocycle as molecular rigid core have been prepared in good yield. All of these new compounds show mesomorphic behaviors, good thermal stability and intrinsic fluorescence nature. The physical and electro-optical properties of these liquid crystal materials were evaluated. Their properties can be adjusted by varying the alkyl/alkoxyl chain or N-heterocycles. Most of the new compounds exhibit high birefringence, and compounds with propyl chain display stronger fluorescence intensity than those with methoxyl. These tolane-based N-heterocyclic liquid crystals may be used as new high birefringence fluorescent liquid crystal materials. [ABSTRACT FROM AUTHOR]