Search Results (58)

Liquid crystal elastomers (LCEs) are soft, stimuli-responsive materials capable of converting molecular-scale reorientation of mesogenic groups into macroscopic, reversible deformations. In this study, film-shaped LCEs were fabricated via a thiol–ene click reaction and characterized under varying electric-field strengths and tensile loads. The LCEs exhibited pronounced soft elasticity and large, reversible strains due to reorientation of mesogenic groups, in contrast to non-mesogenic elastomers. Dynamic viscoelastic measurements revealed fully reversible changes in storage modulus upon electric-field application, highlighting the critical role of mesogenic group alignment in electromechanical actuation. Electric-field-induced contraction increased with field strength and decreased with tensile load, reaching a maximum of 15% under minimal load, with additional enhancement resulting from mesogenic group reorientation along the thickness direction. Notably, unlike conventional light- or temperature-driven actuation, which is often limited by slow molecular relaxation or heat diffusion, the electric-field-driven LCE exhibited rapid, fully reversible deformation. These findings demonstrate the potential of electric-field-responsive LCEs for applications requiring fast, controllable, and large-strain actuation, and provide insights into the interplay between mesogenic group orientation, mechanical loading, and external stimuli in designing efficient soft actuators. Full article

Photoluminescent liquid crystals with photoluminescence (PL) and liquid-crystalline (LC) properties have attracted attention as PL-switching materials owing to their thermally induced phase transitions, such as crystal → smectic A/nematic → isotropic phase transitions. Our group previously developed tetrafluorinated tolane mesogenic dimers linked by flexible alkylene-1,n-dioxy spacers, demonstrating that the position of the tetrafluorinated aromatic ring critically influences the LC behavior. However, these compounds exhibited very weak fluorescence owing to an insufficient D–π–A character of the π-conjugated mesogens, which facilitated internal conversion from emissive ππ* to non-emissive πσ* states. We designed and synthesized derivatives in which the mesogen–spacer linkage was modified from ether to ester, thereby enhancing the D–π–A character. Thermal and structural analyses revealed spacer-length parity effects: even-numbered spacers induced nematic phases, whereas odd-numbered spacers stabilized smectic A phases. Photophysical studies revealed multi-state PL across solution, crystal, and LC phases. Strong blue PL (Φ_PL = 0.39–0.48) was observed in solution, while crystals exhibited aggregation-induced emission enhancement (Φ_PL = 0.48–0.77) with spectral diversity. In LC states, Φ_PL values up to 0.36 were maintained, showing reversible intensity and spectral shifts with phase transitions. These findings establish design principles that correlate spacer parity, phase behavior, and PL properties, enabling potential applications in PL thermosensors and responsive optoelectronic devices. Full article

Fluorescent liquid crystals (LCs) have attracted considerable interest owing to their unique combination of fluidity, anisotropy, and intrinsic emission. However, most reported fluorescent LCs exhibit high phase transition temperatures and/or smectic phases, limiting their practical applications. To address this, we designed and synthesized a series of 2,1,3-benzothiadiazole (BTD)-based fluorescent nematic liquid crystals incorporating donor (D) or acceptor (A) groups to form D–A–D or D–A–A structures. Most of the synthesized derivatives exhibited supercooled nematic phases at room temperature. They composed various functional groups, such as secondary alkylamine, branched alkyl chain, and trifluoroacetyl groups, which are rarely used in calamitic nematic LCs. Notably, dimethylamine- and carbonyl-substituted derivatives exhibited relatively high fluorescence quantum yields (Φ_fl) in both solid and mesophase states, demonstrating their potential as efficient fluorescent materials. Our findings underscore the versatility of BTD-based mesogenic skeletons for designing room-temperature fluorescent nematic LCs with various functional groups. These materials offer promising opportunities for next-generation display technologies, optical sensors, and photonic applications. Full article

A series of triphenylene (TP) compounds—denoted 3,6-THTP-DiCnOH—bearing four hexyloxy ancillary chains and two variable-length alkoxy chains terminally functionalized with hydroxyl groups have been synthesized and characterized. The shorter homologs revealed mesogenic characteristics, giving rise to thermotropic mesophases in which π-stacked columns of H-bound dimers self-organize yielding superstructures. Molecular-scale models are proposed to account for their structural features. The three studied compounds yielded supramolecular gels in methanol; their ability to gelify higher alcohols was found to be enhanced by the presence of water. The intermediate homolog also gelled n-hexane. Compared to their isomeric 2,7-THTP-DiCnOH analogs, the 3,6-derivatives showed a higher tendency to give rise to LC phases (wider thermal ranges) and a lower organogelling ability (variety of gelled solvents, lower gels stabilities). The overall results are analyzed in terms of different kinds of competing H-bonds: intramolecular, face-to-face dimeric, lateral polymeric, and solvent–TP interactions. Full article

By combining molecular dynamics (MD) simulations and density functional theory (DFT), the influence of dye structure on the optical modulation properties of negative-mode guest–host liquid crystal (GHLC) systems was systematically investigated. Firstly, the reliability of the simulation method was validated by comparing the performance parameters of the GHLC system obtained from simulations with those from experimental results. Subsequently, a series of guest dye molecules, along with their mixtures with negative dielectric anisotropy mesogens, were designed and analyzed. This exploration focused on how variations in dye terminal chain lengths, substitution positions, and substituent group properties affect dye molecular geometry, dye alignment within the host, transition dipole orientation, absorption spectra, and electronic excitation properties. Our findings suggest that dye molecules with a flexible terminal chain substitution of five carbon atoms, positioned at the 2 and 6 locations on the anthraquinone core, exhibit higher order parameters, favorable for enhancing dichroic performance. Moreover, introducing different α-substituents further influences the dye orientation and electronic behavior within the host. These results highlight that structural modifications of anthraquinone-based dyes allow for the design of high-dichroic-ratio materials with customized absorption properties. Overall, our results provide a beneficial understanding of the structure–property relation in GHLC systems, offering valuable guidance for designing high-performance dye molecules and advanced optoelectronic materials in future research. Full article

Cyanostilbene (CS)-related conjugated groups can be considered as dual functional groups of AIEgen and mesogen to construct photoluminescent liquid crystals, and it is essential to study the relationship between their molecular structures and compound properties systematically. In this paper, we designed and synthesized linear and bent-shaped CS derivatives containing ester- and amide-connecting groups and different substituted numbers of alkoxy tails. Their phase behaviors and photophysical properties were investigated in depth. The bent-shaped compounds with the mono-substituted alkoxy tail exhibit a smectic C structure, and those containing two or three alkoxy tails possess a hexagonal columnar phase structure. The compounds exhibit aggregation-induced emission (AIE) properties in tetrahydrofuran (THF)/water mixtures. When the water fraction increases to a certain threshold, a dramatic increase in emission intensity and a red-shift in the fluorescence emission peak are detected. The emission peaks of the ester-type compounds in solid states are around 480 nm, and those of the amide-type compounds are extended to 590 nm, exhibiting versatile luminescent colors. Moreover, thermochromic and photochromic fluorescence-responsive properties are witnessed in these CS derivatives. This work provides a new strategy for the design and synthesis of fluorescent liquid crystalline materials with multiple response properties. Full article

Phenylethynyl-terminated imide (PETI) oligomers are highly valued for their diverse applications in films, moldings, adhesives, and composite material matrices. PETIs can be synthesized at varying molecular weights, enabling the fine-tuning of their properties to meet specific application requirements. Upon thermal curing, these oligomers form super-rigid network structures that enhance solvent resistance, increase glass-transition temperatures, and improve elastic moduli. Their low molecular weights and melt viscosities further facilitate processing, making them particularly suitable for composites and adhesive bonding. This review examines recent advancements in developing ultra-high-temperature PETIs, focusing on their structure–processing–properties relationships. It begins with an overview of the historical background and key physicochemical characteristics of PETIs, followed by a detailed discussion of PETIs synthesized from monomers featuring noncoplanar configurations (including kink and cardo structures), fluorinated groups, flexible linkages, and liquid crystalline mesogenic structures. The review concludes by addressing current challenges in this research field and exploring potential future directions. Full article

In this work, we describe the phase behaviour and the dielectric and conductivity response of new light-responsive ionic liquid crystals, ILCs, which can be applied as controllable electrolytes. The materials include two different dicationic viologens, the asymmetric 6BP18 and the symmetric EV2ON(Tf)₂, containing bistriflimide as the counterions, mixed with 5% and 50% molar, respectively, of one new photoresponsive mesogen called CNAzO14. These mixtures exhibit liquid crystal behaviour, light responsiveness through the E-Z photoisomerisation of the azobenzene groups in CNAzO14, and strong dielectric responses. The 5%-CNAzO14/Ev2ON(Tf)₂ mixture displays direct current conductivities in the 10⁻⁷ S·cm⁻¹ range, which can be increased by a two-fold factor upon the irradiation of UV light at 365 nm. Our findings set the grounds for designing new smart ionic soft materials with nanostructures that can be tuned and used for energy conversion and storage applications. Full article

Bent-core liquid crystals, a class of mesogenic compounds with non-linear molecular structures, are well known for their unconventional mesophases, characterized by complex molecular (and supramolecular) ordering and often featuring biaxial and polar properties. In the nematic phase, their unique behavior is manifested in the formation of nano-sized biaxial clusters of layered molecules (cybotactic groups). While this prompted their consideration in the quest for nematic biaxiality, experimental evidence indicates that the cybotactic order is only short-ranged and that the nematic phase is macroscopically uniaxial. By combining atomic force microscopy, neutron reflectivity and wide-angle grazing-incidence X-ray scattering, here, we demonstrate that multilayer films of a bent-core nematic, deposited on silicon by a combined Langmuir–Blodgett and Langmuir–Schaefer approach, exhibit macroscopic in-plane ordering, with the long molecular axis tilted with respect to the sample surface and the short molecular axis (i.e., the apex bisector) aligned along the film compression direction. We thus propose the use of Langmuir films as an effective way to study and control the complex anchoring properties of bent-core liquid crystals. Full article

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. Full article

A new mesogenic non-symmetric dimeric monomer with a terminal olefin function, forming a twist bend nematic (N_tb) as well as a nematic (N) phase, was synthesized, using an enhanced synthetic methodology, which avoids isomerization of the terminal double bond in the preparation of the dimer. This monomer was attached to a pentamethyldisiloxane group, resulting in the SmA LC phase behavior of the ensuing material. Linking the monomer to a siloxane main chain resulted in nematic phase behavior. Detailed studies with the N_tb phase forming dimer DTC5C7 show full miscibility of the dimer and the new LC polymer in the LC state, suggesting that the side-chain LC polymer forms a N_tb phase as the low-temperature nematic phase. Copolymerizing the monomer with a cyanobiphenyl-based monomer allows us to tune the glass transition and phase behavior further. Full article

Dendrimers have a diverse and versatile morphology, frequently consisting of core, linking, and peripheral moieties. Dendrimers with flexible linkers, such as PAMAM, cannot retain the persistent shape of molecules, and this has been widely explored and reviewed previously; nevertheless, dendrimers with stiff linkers can preserve the persistent shape of the dendrimers, which has been reported considerably less. This review thus focuses on addressing shape-persistent dendrimers with rigid linking moieties discovered in recent years, i.e., from 2012 to 2023. Shape-persistent dendrimers with an interstitial gap between the dendritic frames in the solid state may or may not let the intramolecular void space be accessible for guest molecules, which largely depends on whether their peripheral groups are flexible or non-flexible. In this paper, eight articles on shape-persistent dendrimers with a flexible alkyl periphery, which may exhibit mesogenic phases upon thermal treatment, and eight articles on shape-persistent dendrimers with a non-flexible periphery, which may allow external ions, gases, or volatile organic compounds to access the interstitial gaps between dendritic frames, are reviewed. Full article

Different binary phase diagrams, made from two differently substituted three-rings azo/ester and azomethine/ester compounds of the same terminal alkoxy side chain of six carbons, as opposed to the other terminal polar substituent, which can either donate electrons or withdraw electrons including H. The thermal behavior of the prepared derivatives was investigated by differential scanning calorimetry and phases identified by polarized optical microscope. The first group of the binary mixtures was made from laterally F-substituted azo/ester derivatives and their laterally neat analogues. The second group of binary mixtures was made from laterally methoxy-substituted azomethine/ester derivatives and their laterally neat analogues. The final type of investigated phase diagrams was made from the laterally substituted azo and azomethine components bearing different lateral polar groups and different mesogenic moieties. Results were reviewed using phase diagrams that were produced and it was found that different mesomorphic characteristics were seen to depend on the mesogenic component as well as lateral and terminal polar groups. In all cases, these mixtures have been determined to have low melting-temperature eutectic compositions, while linear or negative deviation of nematic or smectic isotropic composition temperature dependence was observed. Full article

Newcastle disease (ND) is endemic in Bangladesh. Locally produced or imported live Newcastle disease virus (NDV) vaccines based on lentogenic virus strains, locally produced live vaccines of the mesogenic Mukteswar strain, as well as imported inactivated vaccines of lentogenic strains, are being used in Bangladesh under different vaccination regimens. Despite these vaccinations, frequent outbreaks of ND are being reported in Bangladesh. Here we compared the efficacy of booster immunization with three different vaccines in chickens that had been primed with two doses of live LaSota vaccine. A total of 30 birds (Group A) were primed with two doses of live LaSota virus (genotype II) vaccine at days 7 and 28, while 20 birds (Group B) remained unvaccinated. At day 60, birds of Group A were divided into three sub-groups, which received booster immunizations with three different vaccines; A1: live LaSota vaccine, A2: inactivated LaSota vaccine, and A3: inactivated genotype XIII.2 vaccine (BD-C161/2010 strain from Bangladesh). Two weeks after booster vaccination (at day 74), all vaccinated birds (A1–A3) and half of the unvaccinated birds (B1) were challenged with a genotype XIII.2 virulent NDV (BD-C161/2010). A moderate antibody response was observed after the primary vaccination, which substantially increased after the booster vaccination in all groups. The mean HI titers induced by the inactivated LaSota vaccine (8.0 log₂/5.0 log₂ with LaSota/BD-C161/2010 HI antigen) and the inactivated BD-C161/2010 vaccine (6.7 log₂/6.2 log₂ with LaSota/BD-C161/2010 HI antigen) were significantly higher than those induced by the LaSota live booster vaccine (3.6 log₂/2.6 log₂ with LaSota/BD-C161/2010 HI antigen). Despite the differences in the antibody titers, all chickens (A1–A3) survived the virulent NDV challenge, while all the unvaccinated challenged birds died. Among the vaccinated groups, however, 50% of the chickens in Group A1 (live LaSota booster immunization) shed virus at 5- and 7-days post challenge (dpc), while 20% and 10% of the chickens in Group A2 (inactivated LaSota booster immunization) shed virus at 3 and 5 dpc, respectively, and only one chicken (10%) in Group A3 shed virus at 5 dpc. In conclusion, the genotype-matched inactivated NDV booster vaccine offers complete clinical protection and a significant reduction in virus shedding. Full article

In this work, hydroxylated compounds are applied to prepare polymer-dispersed liquid crystal (PDLC) films and the role of the hydroxy group is studied in detail by comparing the effects of the hydroxylated acrylate monomer, the hydroxylated mesogenic component and their corresponding non-hydroxylated components. It is revealed that the hydroxylated acrylate monomer plays a more important role in modifying the morphology of the polymer matrix and thereby the electro-optical performance of the PDLC films. Parameters of the polymer matrix, such as size and density of voids, can be affected by various components, but only the hydroxylated acrylate monomer can alter its type from the typical Swiss-cheese type to the polymer-microsphere type. Essentially, the hydroxylated mesogenic component takes effect through changing the ratio of the liquid crystal phase, while the hydroxylated acrylate monomer can participate in the polymerization and impact the development of the polymer matrix. It is anticipated that this research can help in understanding the role of the hydroxy group in PDLC films. Full article