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As the temperature decreases, rigid anisotropic molecules that usually incorporate polar groups, aromatic rings or multiple bonds, orient along a common direction, eventually forming liquid-crystalline phases under specific thermodynamic conditions. This study explores the phase behavior and dynamics of board-shaped mesogens with a 1,4,5,8-tetraphenyl-anthraquinone core and four lateral arms forming an oligo(phenyleneethynylene) scaffold. These molecules are promising candidates for forming the elusive biaxial nematic phase. Through atomistic molecular dynamics simulations, we observe the formation of nematic and smectic liquid crystals, in qualitative agreement with experimental observations. To characterize the structure, we compute pair correlation functions along relevant symmetry directions and the nematic order parameter, which indicate a dominant uniaxial ordering with very weak biaxiality. In addition, we analyze the dynamics of our board-shaped mesogens along and perpendicular to the nematic director, revealing an intriguing non-Gaussian behavior and dynamical heterogeneities, with coexisting slow and fast molecules. Building on our recent simulations at the colloidal scale, which demonstrated that monodisperse board-like particles are unable to form biaxial nematics while polydisperse particles can, we hypothesize that a similar behavior may occur at the molecular scale in mixtures of molecules. Although pure-component molecular systems reveal weak biaxiality, our findings suggest that investigating mixtures of the most promising candidates, those molecules that form nematic or smectic phases, could uncover conditions conducive to the formation of biaxial nematic liquid crystals. [ABSTRACT FROM AUTHOR]

[Display omitted] • Thermoresponsive nanocontainers are synthesized from ionic complexes of polybases. • The complexes can be readily (re)formed by simple mixing of the components. • Resulting comb-like complexes with wedge-shaped ligands exhibit multiscale ordering. • Ligand type controls shape and thermal stability of nanocontainers. • Coarse-grain simulation explores the routes of vesicle and nanocylinders formation. Multi-responsive polymeric nanocontainers attract significant attention for their potential applications in biotechnology, drug delivery, catalysis, and other fields. By incorporating a liquid-crystalline (LC) mesogenic ligand with an alkyl tail length ranging from 8–12 carbons, ionically linked to the polymer backbone, we generate vesicles with walls significantly thinner than those of conventional polymersomes, approaching the thickness of a lipid bilayer. These LC vesicles, ranging in size from 50–120 nm, are designed to be mechanically robust due to the alignment of the hydrophilic polymer backbone within the plane of the vesicle wall. Additionally, incorporating a temperature-sensitive block into the polymer structure imparts thermoresponsiveness to the nanocontainers, enhancing their functionality and adaptability for various applications. Ionic complexes of hydrophilic polybases, specifically poly(2-(dimethylamino)ethyl methacrylate) (PDMAEMA) and PDMAEMA- b -PNIPAM (poly(N -isopropylacrylamide)) block copolymers, with amphiphilic wedge-shaped mesogens bearing a sulfonic acid group at the focal point were synthesized. The designed nanocontainers, in the form of either vesicles or nanotubes, exhibit a well-defined wall thickness of 5 nm, dictated by the organization of a smectic LC phase. The constructed coarse-grained models elucidate the mechanism of self-assembly, demonstrating that the balance between the hydrophilicity of the main polymer chain and the hydrophobicity of the wedge-shaped pendant groups determines both the internal and external structure of the vesicles. [ABSTRACT FROM AUTHOR]

In the development of functional materials, side chains are traditionally incorporated into the primary chemical structure to induce liquid-crystalline behavior or to enhance solubility for improved processability. However, emerging evidence suggests that side chains play a far more complex role. This study presents a case of a double helical supramolecular structure formed by star-shaped mesogens in the absence of specific interactions. The molecular conformation is primarily dictated by the self-assembly of the side chains, introducing a new organizational paradigm for semiflexible low-molecular-weight mesogens. [ABSTRACT FROM AUTHOR]

Block copolymers (BCPs) have attracted considerable attention due to their ability to form a variety of complex assemblies with diverse morphologies and functions in solution. By incorporating liquid crystalline (LC) moieties, the LC side chains significantly affect the morphologies and sizes of BCP assemblies. In this study, we synthesized the copolymer with an LC block containing triphenylene (HAT) discotic mesogen and short methylene side chains. By enhancing the π–π interaction between triphenylene discotic mesogens, and doping the discotic mesogens, the LC orderedness was significantly enhanced and able to dictate the self-assembly behaviors of the BCP in solution. Additionally, the lengths of resultant fibrillar micelles were easily tuned by adjusting the dopant content. More interestingly, two growth modes, nucleation growth and coupling, were observed during the formation of fibrils. Consequently, with long-term aging and sufficient concentration, a large portion of these fibrils underwent end-to-end coupling to form long fibrils, allowing the formation of organogel via inter-fibrillar entanglement. [ABSTRACT FROM AUTHOR]

Any polymers composed of racemic segments are obviously optically inactive and lack any chiroptical applications. Here, we present an intriguing method for precisely generating global chirality in racemic copolymer assemblies without any external asymmetrical intervention via step‐wise polymerization‐induced chiral self‐assembly (PICSA). Global supramolecular chirality of the nanoaggregates could be dynamically switched by the two diametrically opposed chiral conflict effects: “first come, first serve” effect and “late‐comer lives above” effect, which can be controlled by the precisely specified the number and sequence of enantiomeric segments. Significantly, the supramolecular stacking manners of the racemic mesogenic building units as well as the liquid crystallinity of the solvophobic core play a crucial role for the chiral communication pathway of enantiomeric mesogens. Furthermore, such switchable global chirality in racemic polymers is broadly applicable and well regulable. We propose that this research may challenge the notion that racemic systems lack optical activity while highlighting their potential applications in functional racemic polymer materials and providing insights into the evolution of racemates towards homochirality on early Earth. [ABSTRACT FROM AUTHOR]

We have investigated the effect of adding polar rodlike nanoparticles (NPs) to a liquid crystal using Monte Carlo simulations. The mesogens (Ms) are represented with Gay–Berne elongated ellipsoids endowed with a central axial electric dipole. A NP is instead modelled by a overall rod-like set of rigidly assembled Lennard–Jones spherical beads (Orlandi et al. Phys. Chem. Chem. Phys. 18, 2428–2441 (2016). doi:10.1039/C5CP05754J) that are either non-polar or endowed with a central axial dipole of different strengths. We consider two cases: one of strong NP-M affinity and weak NP-NP interactions (case 1) and the opposite one of weak NP-M affinity and strong NP-NP interactions (case 2). We find that for case 1 adding polar NPs slightly lowers the nematic-isotropic transition temperature $ T_{NI} $ T NI which instead, for case 2, is essentially unaffected. Having strongly polar, instead of non-polar NPs reduces the $ T_{NI} $ T NI difference with the pristine one, while significantly increasing the dielectric anisotropy in the nematic phase, which could be useful in applications. [ABSTRACT FROM AUTHOR]

Mesogens, which are typically stiff rodlike or disklike molecules, are able to self-organize into liquid crystal (LC) phases in a certain temperature range. Such mesogens, or LC groups, can be attached to polymer chains in various configurations including within the backbone (main-chain LC polymers) or at the ends of side-chains attached to the backbone in an end-on or side-on configuration (side-chain LC polymers or SCLCPs), which can display synergistic properties arising from both their LC and polymeric character. At lower temperatures, chain conformations may be significantly altered due to the mesoscale LC ordering; thus, when heated from the LC ordered state through the LC to isotropic phase transition, the chains return from a more stretched to a more random coil conformation. This can cause macroscopic shape changes, which depend significantly on the type of LC attachment and other architectural properties of the polymer. Here, to study the structure–property relationships for SCLCPs with a range of different architectures, we develop a coarse-grained model that includes torsional potentials along with LC interactions of a Gay–Berne form. We create systems of different side-chain lengths, chain stiffnesses, and LC attachment types and track their structural properties as a function of temperature. Our modeled systems indeed form a variety of well-organized mesophase structures at low temperatures, and we predict higher LC-to-isotropic transition temperatures for the end-on side-chain systems than for analogous side-on side-chain systems. Understanding these phase transitions and their dependence on polymer architecture can be useful in designing materials with reversible and controllable deformations. [ABSTRACT FROM AUTHOR]

This study focuses on the helical conformation of the main chain of syndiotactic poly(substituted methylene)s with 4‐cyanobiphenyl (CB) moieties incorporated at the ends of the alkyloxycarbonyl side chains. The polymers are designated as PCBn, where n is the number of methylene units in the spacer between the main chain and CB. PCB6 and PCB8 assemble the side chains into layers without positional order within the layers. Meanwhile, PCB10 and PCB12 assemble the side chains into layers with a short‐range positional order. Each CB moiety at a side chain end is bonded to a carbon atom, which is arranged along the helical main chain contour, and its position correlates with that of the carbon atom. As the temperature increases, PCB10 undergoes a phase transition, losing the positional order of the side chains within a layer, which alters the main chain conformation. Consequently, the positions of the side‐chain CB moieties affect the helical conformation of the main chain. In contrast, PCB12 maintains the main chain conformation when undergoing a phase transition similar to that of PCB10. PCB12 with the longer spacer allows the main chain to adopt a helix conformation, which is independent of the positions of side‐chain CB moieties. [ABSTRACT FROM AUTHOR]

A coarser model for the Gay-Berne mesogen is developed using the interaction potential from the Approximate Non-Conformal (ANC) theory. The ANC potential contains both repulsive and attractive contributions. We modify intermolecular attractions by conditioning them with a Hess-Su orientation-dependent term. This imparts an anisotropic contribution to the energy of the system. The softness parameter s of the ANC potential is probed to qualitatively identify a threshold capable of sustaining a nematic phase. We construct phase diagrams for each value of s from molecular dynamics simulations and characterise bulk samples to outline phase regions. We find that a softness parameter $ s \sim 0.6 $ s ∼ 0.6 or higher supports the emergence of a nematic phase. The stability of the nematic region is enhanced as $ s\to 1 $ s → 1 , corresponding to the conventional Lennard-Jones interaction. The stability of the nematic phase for nearly-spherical mesogens with increasing s leads to a gradual loss in spherical symmetry despite no imposed shape anisotropy. Thus, the energy anisotropy becomes more pronounced and is capable of prompting the emergence of the nematic phase in this model. [ABSTRACT FROM AUTHOR]

Liquid-liquid phase separation, whereby two liquids spontaneously demix, is ubiquitous in industrial, environmental, and biological processes. While isotropic fluids are known to condense into spherical droplets in the binodal region, these dynamics are poorly understood for structured fluids. Here, we report the unique observation of condensate networks, which spontaneously assemble during the demixing of a mesogen from a solvent. Condensing mesogens form rapidly elongating filaments, rather than spheres, to relieve distortion of an internal smectic mesophase. As filaments densify, they collapse into bulged discs, lowering the elastic free energy. Additional distortion is relieved by retraction of filaments into the discs, which are straightened under tension to form a ramified network. Understanding and controlling these dynamics may provide different avenues to direct pattern formation or template materials. [ABSTRACT FROM AUTHOR]

Two star‐shaped mesogens with a (meso‐tetraphenylporphinato) zinc (II) core and bithiophene conjugated arms with 3,4,5‐trisdodecyloxyphenyl periphery were synthesized. One of these molecules was decorated with four fullerenes via an aliphatic spacer. This is the sterically overcrowded compound with an octapodal morphology. The other star lacks the fullerenes and provides free space between the conjugated arms. This mesogen does not aggregate in solution, but in solid state it forms a hexagonal columnar and a highly ordered oblique helical columnar phase, while the octopus molecule assembles in an amorphous solid. Photophysical studies of the octapodal compound in solution and the solid thin film reveal the formation of J‐type aggregates, in which the interaction between donors (porphyrin) and acceptors (fullerene) dominates leading to absorption bands in the NIR region of the spectra. The mixture of both compounds results in a self‐assembly which is called the Click procedure. Fullerenes of the octopus nanosegregate in the pockets of the star mesogens generating hexagonal columnar structures with a regular stacking along the columnar axis. Thus providing free space is a tool to control the competition between supramolecular interactions and nanosegregation. Such liquid‐crystalline donor‐acceptor structures may play a role in future LC photovoltaic applications. [ABSTRACT FROM AUTHOR]

Mechanical stretching is commonly used for mesogen alignment which is essential for the muscle-like actuations of liquid crystal elastomers (LCEs). Despite the simplicity of the method, the mesogens are typically aligned in the stretching direction, limiting exclusively the LCE to an actuation mode of cooling-induced elongation. Here, we design an interpenetrating double network consisting of an LCE network and an elastomer network, with one polymerized network stretched before the polymerization of the other network. Depending on the polymerization sequence of the two networks, the double network shows two opposite actuation modes, namely, the conventional cooling-induced elongation or an unusual cooling-induced contraction. Strategic integration of the two opposite behaviors into the same LCE leads to sophisticated actuation difficult to achieve with a conventional LCE design. Coupled with 3D printing, geometrically complexed LCEs with diverse multimodal four-dimensional actuation behaviors are illustrated. Our work expands the design scope of LCE actuators and their potential device applications. [ABSTRACT FROM AUTHOR]

Liquid crystals, which have both liquid and solid properties, inevitably exhibit fluctuations. Some frustrated liquid-crystalline phases with a hierarchical structure, such as cybotactic nematic, modulated smectic, and bicontinuous cubic phases, are fascinating fluctuation-induced phases. In addition to these equilibrium phases, a pattern formation that is a nonequilibrium order through fluctuation is one of the most attractive research areas in soft matter. In this review, the studies on producing these fluctuation-induced orders in liquid crystals are described. Liquid-crystalline supermolecules in which several mesogens are connected via a flexible spacer have been designed. They have not only a characteristic shape but also an intra-molecular dynamic order. The supermolecules induce the fluctuations in layer structures at a molecular level, producing from the frustrated hierarchical to dynamic dissipative structures. In addition to reviewing molecular design for the hierarchical structures, the pattern propagation in a smectic phase is discussed based on the rotation of smectic blocks through Rayleigh–Bénard convection. [ABSTRACT FROM AUTHOR]

Liquid crystal-forming cyanobiphenyls are truly extraordinary molecules that have had an enormous impact on liquid crystal research and applications since they were first synthesised. This impact is, on the one hand, due to the exceptionally convenient physical properties of the main characters, 5CB and 8CB, allowing easy experiments at room temperature, as well as their commercial availability at reasonable cost. On the other hand, the cyanobiphenyl chemical structure leads to some quite peculiar characteristics in terms of organisation at the molecular scale, which are sometimes well recognised and even utilised, but often the awareness of these peculiarities is not strong. This perspective article reviews the use of cyanobiphenyls in making liquid crystal shells and liquid crystal core fibres, in sensing, as a medium for simultaneously aligning and dispersing carbon nanotubes, and as highly useful solvents for reactive mesogens that can be polymerised into anisotropic networks. This choice is very much motivated by how cyanobiphenyls have impacted our group's research throughout the years, which is the basis for the examples I provide. Nevertheless, I believe they serve well to illustrate the immense usefulness of cyanobiphenyls in innovating research and applications related to liquid crystals. [ABSTRACT FROM AUTHOR]

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The liquid crystal state (LC) in polymer chemistry is a topic discussed in varied materials research. The anisotropic properties typical of these compounds are mostly the result of the presence of mesogens in the structure of liquid crystals. This article traces the development of liquid crystal science, focusing on liquid crystal epoxy resins (LCERs) and emphasizing the crucial role of mesogens and their diverse effect on the materials. It also highlights the importance of understanding the morphology of LC polymers, explaining their profound impact on material properties and performance. It explores the cross-linking process of liquid crystal resins and composites, describing how changes in structural factors affect material structure. The article also provides information about hardeners and their influence on the cross-linked structure. Various nanofillers were also discussed, elucidating their impact on the resulting composites. [ABSTRACT FROM AUTHOR]

Recently, a large family of at least 14 discotic liquid crystals was discovered that are exceptions to the conventional paradigm that discotic mesogens tend to feature long, flexible tails on their periphery. To understand why these materials are liquid crystals, as well as the structural determinants of discotic phase behavior, we studied a group of closely related small tail-free disk-like molecules, including both mesogenic and non-mesogenic compounds differing only in the position of a single fluorine substituent. The rigidity and structural simplicity of these molecules make them well suited to for study by large, fully all-atom simulations. Using a combination of static and dynamic metrics, we were able to identify several key features of the columnar mesophase and, thereby, conclusively identify a columnar liquid crystalline mesophase present in a subset of our systems. Our simulations feature molecules hopping between columns in the columnar mesophase and distinctive molecular rotations in 60° steps about the columnar axis. The ability to create and characterize columnar mesophases in silico provides a potent tool for untangling the structural determinants of liquid crystalline behavior in these and other tail-free discotic liquid crystals. [ABSTRACT FROM AUTHOR]

Solution-state self-assemblies of block copolymers to form nanostructures are tremendously attractive for their tailorable morphologies and functionalities. While incorporating moieties with strong ordering effects may introduce highly orientational control over the molecular packing and dictate assembly behaviors, subtle and delicate driving forces can yield slower kinetics to reveal manifold metastable morphologies. Herein, we report the unusually convoluted self-assembly behaviors of a liquid crystalline block copolymer bearing triphenylene discotic mesogens. They undergo unusual multiple morphological transitions spontaneously, driven by their intrinsic subtle liquid crystalline ordering effect. Meanwhile, liquid crystalline orderedness can also be built very quickly by doping the mesogens with small-molecule dopants, and the morphological transitions are dramatically accelerated and various exotic micelles are produced. Surprisingly, with high doping levels, the self-assembly mechanism of this block copolymer is completely changed from intramolecular chain shuffling and rearrangement to nucleation-growth mode, based on which self-seeding experiments can be conducted to produce highly uniform fibrils. Assembly of block copolymers can be controlled to give varying morphologies and functionalities, but there are still aspects of the process that are not well understood. Here, the authors report convoluted self-assembly behaviours of block copolymers with discotic liquid crystalline moieties. [ABSTRACT FROM AUTHOR]

A novel homologous series of cinnamoyl ester comprising of elven (C1 to C16) homologues liquid crystal (LC) samples have been synthesized and characterized using instrumental methods (spectral and thermal) of analysis and DFT approach. As results, middle ordered melting type of series with exhibition of nematic mesophase were observed. The observed mesogenic properties and transition temperature are affected by the size of alkyl chains that shows mesomorphism is susceptible to molecular structure. The prepared LCs of cinnamoyl ester derivatives were further examined for their biological activities and the obtained results indicates a good biological potential for the studied LC materials. [ABSTRACT FROM AUTHOR]

Liquid crystalline nanoparticles (LC NPs) are a kind of polymer NPs with LC mesogens, which can form special anisotropic morphologies due to the influence of LC ordering. Owing to the stimuli‐responsiveness of the LC blocks, LC NPs show abundant morphology evolution behaviors in response to external regulation. LC NPs have great application potential in nano‐devices, drug delivery, special fibers and other fields. Polymerization‐induced self‐assembly (PISA) method can synthesize LC NPs at high solid content, reducing the harsh demand for reaction solvent of the LC polymers, being a better choice for large‐scale production. In this review, we introduced recent research progress of PISA‐LC NPs by dividing them into several parts according to the LC mesogen, and discussed the improvement of experimental conditions and the potential application of these polymers. [ABSTRACT FROM AUTHOR]

The recent identification of ferroelectricity within the nematic phase of liquid crystals has triggered significant interest. However, prior to this discovery; the potential existence of ferroelectricity in the nematic phase had already been investigated in the context of cybotactic nematic phases of liquid crystals. Ferroelectricity has previously been reported in chiral and achiral smectic phases. While the presence of nano-sized smectic clusters in the nematic phase of rod-shaped molecules, termed as cybotactic nematic, was recognised, it did not earn substantial attention. However, the cybotactic nematic phase in bent-core mesogens has gained significant attention due to its unconventional ferroelectric-like behaviour. To link the recent advancements in understanding ferroelectricity in the nematic phase, a comprehensive review has been conducted on the cybotactic nematic phase. This review encompasses a foundational explanation of the cybotactic model, followed by an overview of cybotactic phases in rod-shaped mesogens. The central focus lies in evaluating cybotactic phases within bent-core nematic systems, covering early debates, fundamental experimental evidences, and a compilation of mesogens that exhibit the cybotactic nematic phase. Furthermore, the review describes into the physical attributes of mesogens featuring cybotactic nematic phases, including discussions on repolarisation, dielectric properties, and optical characteristics. [ABSTRACT FROM AUTHOR]

To develop smart ionic skins capable of multi‐responsiveness and switchable ionic conductivity, a stimuli‐responsive and ionic conductive azobenzene‐based monomer is newly synthesized, uniaxially oriented, and polymerized for anisotropic liquid crystal elastomers (LCEs). Since the uniaxially oriented monodomain LCE with ionic asymmetric azobenzene monomers (i‐AAM) is prepared by thermal oligomerization, uniaxial stretching, and subsequent photopolymerization, the stimuli‐responsive i‐AAM LCE is thermally contracted by increasing the temperature above TNI as well as is bent along the aligned direction by irradiating it with UV light. In addition to the change of shape, the ionic conductivity of the LCE is reversible in response to heat and light stimuli. Polydomain i‐AAM LCE polymerized without the stretching process exhibits higher ionic conductivity than stretched monodomain LCE due to the initially formed stable ionic pathways. Ionic conductivity can also be switched simultaneously by polarity changes in response to the photoisomerization of i‐AAM, increased mobility from heat, and an elastic mechanoresponse from external stresses. These i‐AAM LCE‐based soft grippers exhibit stimuli‐responsive grasping and releasing actuation and detect ionic conductivity switches finely, suggesting potential as smart skins for advanced soft robots. [ABSTRACT FROM AUTHOR]

First series of fluorescein-based hexacatenar mesogens consisting of a central fluorescein unit and two 1,2,3-triazole dendritic wings were designed and synthesized by using the Williamson reaction and Cu-assisted alkyne-azide cycloaddition reaction. Polarized optical microscopy textures, differential scanning calorimetry curves, and X-ray diffraction (XRD) data demonstrated that all the compounds can self-assemble into hexagonal columnar mesophases. Organogel test demonstrated that these compounds could form organogel in some moderate polar solvents with irregularly winkled morphologies. Density functional theory calculation demonstrated that these mesogens adopted distorted conformation which might be the reason why narrow mesogenic temperature ranges and irregularly winkled morphologies in these compounds are observed. [ABSTRACT FROM AUTHOR]

We have designed new chiral smectic mesogens with the -CH2O group near the chiral center. We synthesized two unique rod-like compounds. We determined the mesomorphic properties of these mesogens and confirmed the phase identification using dielectric spectroscopy. Depending on the length of the oligomethylene spacer (i.e., the number of methylene groups) in the achiral part of the molecules, the studied materials show different phase sequences. Moreover, the temperature ranges of the observed smectic phases are different. It can be seen that as the length of the alkyl chain increases, the liquid crystalline material shows more mesophases. Additionally, its clearing (isotropization) temperature increases. The studied compounds are compared with the structurally similar smectogens previously synthesized. The helical pitch measurements were performed using the selective reflection method. These materials can be useful and effective as chiral components and dopants in smectic mixtures targeted for optoelectronics and photonics. [ABSTRACT FROM AUTHOR]

Three homologous series of 3‑hydroxy-4-(((-4-benzoxazol-2-yl)phenyl)imino)methyl)phenyl-4-alkoxybenzoate (with ester linkage) and 5-(alkoxy)-2-(((4-(5-benzoxazol-2-yl)phenyl)imino)methylphenol (without ester linkage) Schiff based derivatives, bearing different substituents at 5 position i.e., 5-methylbenzoxazole, benzoxazole and 5-chlorobenzoxazole units at the end of the molecule and their Copper complexes were synthesised. The molecular structure of all the compounds were elucidated by different spectroscopic techniques such as FT-IR, 1H & 13C NMR and mass spectrometry together with elemental analysis. Their phase transition behaviour was investigated by differential scanning calorimetry, polarizing optical microscopy and X-ray diffraction. The structure-property relationships, compounds bearing a variety of polar substituents and changing the spacer from ester linked to without ester-linked has been studied. Substituents with stronger electron-withdrawing properties gave a wider mesomorphic temperature domain, in the order Cl > CH3 >H.

Synthesis of a new series of mesogenic dimers and investigation of their liquid crystalline properties with thermal, optical and XRD methods is reported. Unlike dimeric mesogens studied to date, the presently reported dimers are derived from a single-ring mesogen containing a partially fluorinated dodecyl chain, which effects nanosegregation and formation of a lamellar phase. The reported four diesters with the odd-membered connecting alkyl chain exhibit a SmA phase. In contrast, two even-membered analogues have higher melting points and do not exhibit mesogenic behaviour. [ABSTRACT FROM AUTHOR]

This review highlights research topics like chiral phases (cholesterics, blue phases and polar phases), structural variations of the mesogens (kinked mesogens, polyphilic mesogens) and various aspects of liquid crystalline polymers. It closes by describing recent aspects like LC-materials from renewable resources, experiments in the ISS and ferroelectric nematic phases. [ABSTRACT FROM AUTHOR]

This work presents the synthesis and self-organization of the calamitic fluorinated mesogen, 1,1,2,2–tetrafluoro–2–(1,1,2,2–tetrafluoro–4–iodobutoxy)ethanesulfonic acid, a potential model for perfluorosulfonic acid membranes (PFSA). The compound is derived in three steps from 1,1,2,2–tetrafluoro–2–(1,1,2,2–tetrafluoro–2–iodoethoxy)ethanesulfonyl fluoride, achieving a 78% overall yield. The resulting compound exhibits intricate thermal behavior. At 150 °C, a crystal-to-crystal transition is observed due to the partial disordering of calamitic molecules, which is followed by isotropization at 218 °C. Upon cooling, sample ordering occurs through the formation of large smectic liquid crystalline phase domains. This thermotropic state transforms into a layered crystal phase at lower temperatures, characterized by alternating hydrophilic and hydrophobic layers. Using X-ray diffraction, crystalline unit cell models at both room temperature and 170 °C were proposed. Computer simulations of the molecule across varying temperatures support the idea that thermal transitions correlate with a loss of molecular orientation. Importantly, the study underscores the pivotal role of precursor self-organization in aligning channels during membrane fabrication, ensuring controlled and oriented positioning. [ABSTRACT FROM AUTHOR]

The steroidal derivatives have been found to be extremely good mesogens since their origin. Due to their inherent chirality, they have the potential to induce a wide variety of liquid crystalline phases, including frustrated phases, depending on the structure of the steroidal skeleton and the substituents attached. In this report, thirteen new homologous Schiff's base derivatives were synthesised by condensing 4-n-alkoxy aniline with 4-formyl phenyl cholesteryl carbonate. All the compounds were characterised using elemental analysis, FT-IR, 1H-NMR and 13C-NMR. In order to study the liquid crystalline behaviour of the synthesised compounds, optical texture studies were carried out using polarising optical microscope in heating and cooling cycles. The derivatives showed a variety of mesophases, including chiral nematic (N*), twist grain boundary-A (TGBA), smectic A (SmA) and chiral smectic C (SmC*) phases. The thermal behaviour was determined using a differential scanning calorimeter and thermogravimetric analysis. All the synthesised compounds are UV-active and show photoluminescence in the blue emission region with good quantum yield. [ABSTRACT FROM AUTHOR]

The present investigation focuses on the geometrical optimized parameters, IR and raman activity based on vibrational frequencies, and global reactivity descriptors of mesogens namely; para-azoxyanisole (PAA), ethyl para-azoxybenzoate (EPAB) and non-mesogen biphenyl-4-carboxylic acid (BCA) molecules via the Density functional theory (DFT) and Hartree–Fock (HF) technique accompanied with 6–31++G (d, p) basis set. The wavenumbers/frequencies obtained for utmost of the vibrational modes are in the predicted range but with minimal error. Reactivity of these molecules based on the molecular properties viz., HOMO, LUMO energies, ionization potential, electro negativity, chemical potential, electron affinity, chemical hardness, and softness has also been focused. The DFT method considers all different electronic interactions thereby give accurate results as compared to Hartree–Fock method. The azoxy bond plays an important role in chemical bond formation in liquid crystals, chemical intermediates, process control, and pharmaceuticals etc. Further, the estimated band gap values indicate the understanding of fine tuning mechanism for exploring the possible industrial applications. [ABSTRACT FROM AUTHOR]

A systematic study of a binary system composed of 4-n-pentyl 4′-cyanobiphenyl (5CB) and 4-n-pentyl phenyl 4-n′-hexyloxy benzoate (ME6O.5) mesogens showing an induced smectic A at different molar concentrations has been done. Heat capacity and optical birefringence measurements have been performed around the N-SmA phase transition region. The heat capacity peaks could be fitted well below the N-SmA transition by means of an extended Landau mean-field model. The first-order nature of the transition throughout the composition range can be inferred. This transition is rather close to the tricritical point when the nematic range is sufficiently increased. The latent heat decreases with the increase in the nematic range. For large nematic range, the latent heat drops to zero and the heat capacity peak associated with N-SmA phase transition disappear, contrary to previously reported most of the usual N-SmA phase transition. Precision birefringence measurements also agree well with the heat capacity data. [ABSTRACT FROM AUTHOR]

Using a thermodynamic model developed by us to study the structural and electro-optical properties of ${\rm Sm\; C}_{\rm A}^{\rm \ast }$ Sm C A ∗ phase, we investigate the temperature dependence of helical pitch, tilt angle and spontaneous polarization of a homologous series of fluorinated biphenyl benzoate esters (3FnHBM6, n = 2, 5, 7) and one of the series W-316-3 obtained from the mixture of two chiral liquid crystalline compounds 6F2OBi and 3F6HBM6. The free-energy density of the system exhibiting ${\rm Sm\; C}_{\rm A}^{\rm \ast }$ Sm C A ∗ phase is written as an expansion series in terms of all the relevant degrees of freedom: ${\bf Q}_{{\bf ij}}$ Q i j , ψ, P, q and the resulting coupling terms between these order parameters. The values of Landau coefficients are determined from the experimental data of antiferroelectric mesogens 3FnHBM6 (n = 2, 5, 7) and W-316-3 in the ${\rm Sm}\; {\rm C}_{\rm A}^{\rm \ast }$ Sm C A ∗ phase. Using these coefficients, the electro-optical and structural properties have been studied. We have found good agreements between the theoretical and experimental results. [ABSTRACT FROM AUTHOR]

Chemical, optical, and thermal characterization are carried out for seven hydrogen bond thermotropic liquid crystalline complexes formed between pentyloxy benzoic acid (5BAO) and p-n-alkyl benzoic acids (nBA, where n refers alkyl carbon chain length which varies from ethyl to octyl. FTIR, ¹H, and 13C Nuclear Magnetic Resonance (NMR) establishes the chemical investigations. Nematic and smectic F are the mesophases observed. Polarizing Optical Microscopic (POM) studies ensures the mesophases identified. Thermal investigation using Differential Scanning Calorimeter (DSC), provides the phase transition temperatures, enthalpy values, thermal stability factor, specific heat capacity values, and thermal equilibrium of the mesogenic complexes. [ABSTRACT FROM AUTHOR]

Previous theoretical studies of calamitic (i.e., rod-like) ionic liquid crystals (ILCs) based on an effective one-species model led to indications of a novel smectic-A phase with a layer spacing being much larger than the length of the mesogenic (i.e., liquid–crystal forming) ions. In order to rule out the possibility that this wide smectic-A phase is merely an artifact caused by the one-species approximation, we investigate an extension that accounts explicitly for cations and anions in ILCs. Our present findings, obtained by grand canonical Monte Carlo simulations, show that the phase transitions between the isotropic and the smectic-A phases of the cation–anion system are in qualitative agreement with the effective one-species model used in the preceding studies. In particular, for ILCs with mesogens (i.e., liquid–crystal forming species) carrying charged sites at their tips, the wide smectic-A phase forms, at low temperatures and within an intermediate density range, in between the isotropic and hexagonal crystal phases. We find that in the ordinary smectic-A phase, the spatial distribution of the counterions of the mesogens is approximately uniform, whereas in the wide smectic-A phase, the small counterions accumulate in between the smectic layers. Due to this phenomenology, the wide smectic-A phase could be interesting for applications, which hinge on the presence of conductivity channels for mobile ions. [ABSTRACT FROM AUTHOR]

Antiferroelectricity is a desirable property of liquid crystalline materials. Therefore, we synthesised and studied two new chiral rod-like mesogens with a molecular core based on two biphenyls connected via ester linkage, with the phenyl substituted by a fluorine atom. The studied mesogens are characterised by nuclear magnetic resonance spectroscopy and mass spectrometry analysis. They have methyl heptyl in the chiral chain and exhibit an antiferroelectric phase in a very broad temperature range. We investigated their mesomorphic properties and confirmed the phase identification by differential scanning calorimetry and broad-frequency dielectric spectroscopy measurements. Additionally, we compared the studied mesogens with previously synthesised analogous materials. Two mixtures were formulated using a base mixture and new mesogens. The helical pitch of the synthesised mesogens and formulated mixtures was estimated using the selective reflection method. [ABSTRACT FROM AUTHOR]

Structurally simple two rod-like mesogens with a three-ring core consisting of biphenyl and phenyl rings are synthesised to investigate the mesophase properties, molecular organisation and the orientational order parameter. In mesogen-1, a dodecyloxy terminal chain is present on the biphenyl ring while the phenyl ring is free from substituent. For mesogen-2, in addition to the dodecyloxy chain, the butyl chain is placed on the phenyl ring. The Hot-stage optical polarising microscopy (HOPM) and differential scanning calorimetry (DSC) measurements show smectic A (SmA), smectic B (SmB), and crystal E (CryE) phases for mesogen-1 and SmA, smectic C (SmC) and smectic F (SmF) phases for mesogen-2. The presence of smectic mesophases is established by X-ray Diffraction (XRD). 1D and 2D 13C solid-state NMR experiments are performed in smectic mesophases to find the orientational order parameters of the phenyl rings of the core. The main order parameter (Szz) of the mesogens in the SmB and SmF phase is in the range of 0.87–0.93. The excellent spectral resolution noticed in 13C NMR spectra in the SmB mesophase (mesogen-1) indicates that the internal rotations of the molecules along the long axis are primarily unhindered. [ABSTRACT FROM AUTHOR]

Spiropyran (SP) based mechanochromic systems are intensively interesting in the research area of mechanochromic materials. Herein, an SP mechanophore is chemically incorporated into a liquid crystalline elastomer (LCE) network through Michael addition. The rigidity of mesogens and the orientation of polymer main chains, in which the aligned mesogens and SP moieties are covalently attached, facilitate the transduction of applied force to SP mechanophore to trigger mechanochromic reaction. The LCE network provides enough elasticity for mechanochromic activation. The obtained SP‐LCEs demonstrate strong and reversible mechanochromic response upon mechanical compression. The mechanochromic efficiency and sensitivity are substantially enhanced by doping the SP‐LCE matrix with nano zinc oxide such that it is easy to write on the material surface by using a thin iron wire. The authors hope such SP‐LCE materials will be further developed for real‐time stress detection applications. [ABSTRACT FROM AUTHOR]

In this work, we aim to model the reorientation process of mesogens in nematic liquid crystal elastomers within the context of dynamics. We consider a continuum model with separate mappings for the deformation of the monolithic material and the orientation of the nematic director, where the latter describes the inclination of the mesogens. We achieve the inextensibility of the nematic director through the introduction of drilling degrees of freedom. We combine this approach with the application of the principle of virtual power and a mixed finite element formulation, in order to formulate distinct momentum and angular momentum balance laws for the two separate mappings. Furthermore, we include in our continuum model a volume load and a surface load associated only with the orientation mapping. We show in the presented three numerical examples that our formulation enables the fulfillment of all momentum and angular momentum balance laws. [ABSTRACT FROM AUTHOR]

A number of wedge-shaped amphiphilic mesogens, derivatives of 1,2,3-tris(dodecyloxy)-benzene, which are precursors of polymer ion conducting membranes, were synthesized. The synthesized compounds included asymmetric 2,3,4-tris(dodecyloxy)benzenesulfonic acid and its sodium and pyridine salts. The self-organization processes of the synthesized mesogens were studied in thin films at different temperatures. Thermotropic liquid crystalline properties of these compounds were studied by DSC method. The structure of the liquid crystalline phases was studied using polarized thermooptical microscopy and X-ray diffraction. The influence of an orientation of magnetic field vector on phase composition of thin films was analyzed. It was shown that the texture of mesogenic films containing different counterions can be controlled by a combination of heating and applying a magnetic field. [ABSTRACT FROM AUTHOR]

Short, partially complementary, single-stranded (ss)DNA strands can form nanostructures with a wide variety of shapes and mechanical properties. It is well known that semiflexible, linear dsDNA can undergo an isotropic to nematic (IN) phase transition and that sufficiently bent structures can form a biaxial nematic phase. Here, we use numerical simulations to explore how the phase behavior of linear DNA constructs changes as we tune the mechanical properties of the constituent DNA by changing the nucleotide sequence. The IN-phase transition can be suppressed in so-called DNA "nunchakus": structures consisting of two rigid dsDNA arms, separated by a sufficiently flexible spacer. In this paper, we use simulations to explore what phase behavior to expect for different linear DNA constructs. To this end, we first performed numerical simulations exploring the structural properties of a number of different DNA oligonucleotides using the oxDNA package. We then used the structural information generated in the oxDNA simulations to construct more coarse-grained models of the rod-like, bent-core, and nunchaku DNA. These coarse-grained models were used to explore the phase behavior of suspensions of the various DNA constructs. The approach explored in this paper makes it possible to "design" the phase behavior of DNA constructs by a suitable choice of the constituent nucleotide sequence. [ABSTRACT FROM AUTHOR]

In this study, novel achiral mesogens containing 4,4'-biphenyl central core connected on both sides through an ester function to 1-(4-(alkyloxy)phenyl)-1 H-[1,2,3]-triazolyl group have been synthesised and characterised. Different mesophases have been identified, with the appearance of both a periodic striped pattern and propeller-patterned droplets close to the transition between the nematic and the smectic-C phases. This periodic texture has been found to be independent of the geometry of the sample cell. These observations suggest a spontaneous symmetry breaking, which can result either from an intrinsic enantioselective self-sorting process with a chirality synchronisation mechanism, or from an extrinsic surface mechanism at the interface between the two phases. [ABSTRACT FROM AUTHOR]

Triphenylene-based pentaalkynylbenzene dyads and naphthophenanthridine derivativediscotic mesogens have been proven a backbone-like utility for modern optoelectronic applications. Herein, we present the charge transport and organic electronic applications of naphthophenanthridine derivatives and a dimer composed of pentaalkynylbenzene (PA) and triphenylene (TP) discotic liquid crystals (DLCs). Naphthophenanthridine derivatives exhibit a hexagonal columnar (Colh) phase; whereas, triphenylene-pentaalkynylbenzene dyads show a columnar centred rectangular (Colr) phase and transform into Colh phase on doping the pure compounds with an electron-acceptor 2,4,7-trinitrofluorenone (TNF) in a 2:1 TNF/compound ratio. The ambipolar charge transport behaviour of the compounds mentioned above has been investigated by the time-of-flight technique. Naphthophenanthridine derivative renders an ambipolar charge transport, showing temperature-independent electron and hole mobility of the order of 3 × 10−4 cm2/Vs; whereas, TP-PA dimer yields an ambipolar charge carrier mobility of order 10−3 cm2/Vs. The phenazine-fused triphenylene DLC shows unipolar hole mobility of the order of 10−4 cm2/Vs; whereas, hydrogen-bonded Hpz-C9-TP DLCs exhibit ambipolar charge mobility of the order of 10−2 cm2/Vs. The high ambipolar charge carrier mobility in the investigated DLC compounds makes them suitable for fabricating organic semiconducting electronic devices. [ABSTRACT FROM AUTHOR]

Columnar mesogens constitute a fascinating class of supramolecular nano‐architectures owing to the exceptional properties induced by their self‐assembling behavior. Extending the π‐conjugated core in such systems by incorporating heteroatoms extensively influences their mesomorphic, photophysical properties, etc., presenting them as potential candidates for optoelectronic applications. In the present work, a series of novel nitrogen and oxygen‐incorporated chromenonaphthophenanthridine‐based elliptical dimers have been synthesized through tandem Pictet‐Spengler cyclization followed by ipso‐aromatic substitution in one‐pot. Mesophase characterization has been carried out by employing POM, DSC, and X‐ray diffraction studies. Photophysical properties were investigated using UV‐vis and emission spectroscopy. Furthermore, the charge transport properties were analyzed by time‐of‐flight measurements, and the observed ambipolar mobilities were found to be of the order of 10−3 cm2 V−1 s−1. The high solubility, excellent thermal stability, self‐organizing properties, and ambipolar charge transport characteristics make them promising candidates for applications in organic electronics. [ABSTRACT FROM AUTHOR]

Liquid crystals (LCs), whose refractive index can be changed by light irradiation, can be used as photoresponsive optical materials. In this study, an LC viologen was proposed as a novel photoresponsive compound that induced a change in the alignment of LC molecules (mesogens). An extended viologen with an asymmetric core, that exhibits a low-order LC phase at room temperature, was mixed with the well-known nematic LC compound (5CB) to prepare homogeneously aligned films. The change in the alignment of the mesogens was successfully induced by triggering a one-electron reduction reaction of the viologen moieties by light irradiation. [ABSTRACT FROM AUTHOR]

A homologous series comprises of eight mesogenic hydrogen bonded liquid crystal (HBLC) referred as nBAO + 4BU BA are designed, synthesized and characterized. All eight mesogens in nBAO + 4BU BA series are subjected to spectral, thermal and optical characterization. Formation of hydrogen bond in the resultant compounds is evinced by FTIR study. All eight mesogens obtained in this series exhibits only nematic phase in their entire thermal spans which are coined as Nematogens. Essential characteristic studies carried out on these nematogens are Parachromatism as a function of temperature, phase transition temperatures,mesogenic thermal span and enthalpy involved during phase transition respectively. [ABSTRACT FROM AUTHOR]

While the halogen bond has been recognised and studied for over a hundred years, it is only in more recent times that chemists have begun to apply it and see its possibilities as another supramolecular interaction that can be deployed in the preparation of materials. This review takes one of those areas, liquid crystals, and considers examples of motifs that have been deployed successfully to generate new mesogens. In particular, rather than attempting to be comprehensive, the article reviews critically data from well‐characterised systems and seeks to first make some comparisons with analogous hydrogen‐bonded materials, before considering how the lability and flexibility of the halogen bond expresses itself in liquid crystal behaviour. [ABSTRACT FROM AUTHOR]

The effect of core fluorination on the mesomorphic properties of rod-like Schiff base-derived liquid crystalline materials was reported. For this purpose, two new series of laterally fluorinated Schiff base liquid crystals are synthesised and investigated in detail. The two series differ from each other's in the length of the terminal alkoxy chain attached to one end of the aromatic core, where in the first series an octyloxy chain is used and in the second series it is replaced by a longer dodecyloxy chain. At the other end in both series of compounds, in addition to the nonsubstituted end (X = H) four different substituents were used (X = CH3O, C6H13O, CH3 and F). The molecular structures of all synthesised compounds were confirmed using different spectroscopic techniques. The molecular self-assembly was investigated using differential scanning calorimetry (DSC) and polarised optical microscope (POM). Depending on the length of terminal alkoxy chain at one end and nature of the substituent X at the other end, different types of mesophases were observed, including nematic and two different types of smectic phases. [ABSTRACT FROM AUTHOR]

Four series of di-flouro, namely; 4-substituted phenylazo-3-flouro phenyl-4'-n-alkoxy 3-flouro phenylazo benzoates (Ina-d) based on aromatic rings with the azo/ester/azo linkages core, were prepared and investigated for their mesomorphic properties. An alkoxy group with chain length varied from n = 6 to 16 is attached to the terminal phenylazobenzoate moiety and the other terminal is a compact group (X = --CH3O, --CH3, H and Br) attached to phenylazo moiety. The mesophases were investigated by DSC and POM and compared with previously investigated dilaterally methyl substituted analogues. Terminally unsubstituted and Br substituted analogues displayed dimorphic N and SmA phases, except the lower homologue (n = 6), while terminally -- CH3O analogues exhibited monomorphic N phase. For terminally -- CH3 substituted, compounds with n = 6-12 exhibited only N phase, while compounds with n = 14 and 16 displayed N and SmA phases. Meanwhile, the dilateral F substituents result in an enhancement in clearing thermal transitions compared with dilateral methyl substituents with a wide mesophase range. TGA analysis revealed that the prepared compounds are thermally stable within mesophase temperature range, except -- CH3O, --CH3 and Br derivatives with n = 6. Binary mixtures of I6a-d/I16a-d derivatives were investigated. The photo-physical property was also studied. [ABSTRACT FROM AUTHOR]

Many studies on the basis of cholesteric liquid crystal (CLC) have focused on dynamic optical changes utilizing photochemical reactions raising helical pitch variations. However, the conventional dyes doped in CLC system often show reversible isomerization such as trans‐cis, E‐Z, and open‐close forms that hampers the fixation of desired color cues. Here, a cyanostilbene‐based reactive mesogen (CSRM) for phototunable and subsequently polymerizable smart CLC paints is newly designed and synthesized. The structural color of the CLC paint can be precisely manipulated in remote controllable manner by inducing a photochemical reaction of CSRM. Due to the irreversible isomerization behaviors of CSRM, the constructed periodic structures with different helical pitches are intactly fixed via in situ photopolymerization under 460 nm light. In addition, the combination of helical nanostructures and cyanostilbene luminophore produces a circularly polarized light emission. The dissymmetry factor of circularly polarized luminescence is dependent on the photoregulated helical nanostructures in CLC films. The decoupled system of triple photofunctionality in a single component of chirophotonic crystalline material is applied to develop advanced optical information storages. [ABSTRACT FROM AUTHOR]