Liquid Crystal Phase Research Articles

Rejuvenating liquid crystal elastomers for self-growth

To date, only one polymer can self-grow to an extended length beyond its original size at room temperature without external stimuli or energy input. This breakthrough paves the way for significant advancements in untethered autonomous soft robotics, eliminating the need for the energy input or external stimuli required by all existing soft robotics systems. However, only freshly prepared samples in an initial state can self-grow, while non-fresh ones cannot. The necessity of synthesizing from monomers for each use imposes significant limitations on practical applications. Here, we propose a strategy to rejuvenate non-fresh samples to their initial state for on-demand self-growth through the synergistic effects of solvents and dynamic covalent bonds during swelling. The solvent used for swelling physically transforms the non-fresh LCEs from the liquid crystal phase to the isotropic phase. Simultaneously, the introduction of the transesterification catalyst through swelling facilitates topological rearrangements through exchange reactions of dynamic covalent bonds. The rejuvenation process can also erase growth history, be repeated several times, and be regulated by selective swelling. This strategy provides a post-modulation method for the rejuvenation and reuse of self-growing LCEs, promising to offer high-performance materials for cutting-edge soft growing robotics.

Review of The Innovative Medication Delivery System: The Cubosome

Cubosomes, also known as bicontinuous cubic phase liquid crystals, are nanoparticles with a specific ratio of amphiphilic lipids as their major constituents. Cubosomes are typically created by hydrating a surfactant or polar lipid that produces a cubic phase and then dispersing it into smaller particles. They operate with solids similar to rheology peculiarities of practical use. They have carvenous (honeycomb) structures that are tightly packed and twisted into three-dimensional bilayers, and they are thermodynamically stable. They can load more drugs because of this type of sophisticated structure. Cubosomes are capable of encapsulating hydrophobic, hydrophilic, and amphiphilic materials. Cubosomes can make drugs that aren't very soluble more soluble. Biocompatible and bioadhesive cubosomes dispersions are available. Due to their characteristics, cubosomes are adaptable systems that can be managed by several ways, including parenterally, percutaneously, and orally. Few researchers have looked into the possibility of cubosomes as delivery methods despite the fact that cubosomes structure has been studied using electron microscopy, light scattering, x-ray, and NMR.

Influence of the counterion on the structure and stability of the smectic C phase in ionic liquid crystals

ABSTRACT Ionic liquid crystals (ILCs) are built of ion pairs. These consist often of a small anion and a large mesogenic cation. The properties of the ILCs like e.g. the phase behaviour or structure parameters, depend not only on the large mesogenic cations but also on the small counteranions. Here the influence of the small anion on the formation and stability of the in ILCs rare smectic C (SmC) phase is investigated in a series of methylimidazolium azobenzene ILCs with the same cation but different anions. All ILCs synthesised show the rare SmC phase. The phase behaviour and the tilt angles of the compounds were studied using polarising optical microscopy and differential scanning calorimetry. Furthermore, layer spacing and layer shrinkage of the SmC phase were examined using X-ray scattering. We show that the structural parameters of the phase-like layer spacing and tilt angle are only weakly influenced by the anions, whereas the mesophase ranges are strongly influenced by the choice of the anions. The results are also compared to the Hofmeister series for anions and it is found that the anions stabilise the SmC phase more the more kosmotropic they are.

Oxacalix[4]arene functionalized macrocycle with columnar liquid crystal phase and self-assembly tuned by reversible photoisomerization process

Oxacalix[4]arene is a unique type of macrocyclic compound closely related to calixarenes. It consists of four aromatic rings connected by oxygen bridges. This molecule exhibits a remarkable blend of rigidity and flexibility, making it adaptable to various molecular interactions. In present study, we present our findings on the synthesis and characterization of four new supramolecular bowl-shaped materials (FOC1-FOC4) originating from the robust core structure of tetranitro oxacalix[4]arene. The thermal decomposition was analyzed through the thermogravimetric analysis. All four oxacalix[4]arene-based macrocycles adopted a 1,3-alternate (saddle-like) conformation and exhibited a columnar hexagonal phase with a behavior to self-assemble at room temperature. All four macrocycles (FOC1-FOC4) displayed enantiotropic mesophases within a temperature range of 56.0 °C to 63.0 °C. Further, the relationship between the molecular structure, particularly the varying alkyl chains, and the mesomorphic properties of these compounds was also examined. It was found that the mesomorphic behavior of FOC3 and FOC4 was significantly influenced by cis and trans isomerization. These two compounds exhibited photoswitching behavior, transitioning between their cis and trans forms when exposed to 365 nm light. Notably, they displayed a prolonged stability in the cis form after UV exposure, which is valuable for applications requiring precise control over the switching process.

Novel AIE liquid crystals with high CPL-active bearing multiple dodecyl/cholesterol-decorated R-BINOL-cyanostilbene

The well-structured circularly polarized luminescence (CPL) active liquid crystal materials (R-BINC-Al and R-BINC-Ch) were synthesized through Suzuki coupling of the R-binaphthyl-cyanostilbene unit, followed by modification with dodecyl chains or cholesterol groups. The influence of chiral sources on the liquid crystal behavior, optical properties, and chiroptical response of R-BINC-Al and R-BINC-Ch was thoroughly investigated. Such results revealed that both molecules exhibited typical aggregation-induced emission (AIE) properties and strong solid-state fluorescence. Concretely, the quantum efficiency (ΦF) values of samples with multiple chiral sources increased from 46 % to 51 % by forming liquid crystals in the smectic C and cholesteric phases, the chirality can be transferred to the cyanostilbene unit through ordered self-assembly in the mesophase, resulting in a significant CPL signal across the molecules. Rightfully, the dissymmetry factor (glum) was increased from -7.92 × 10–3 to -1.53 × 10–2 with the introduction of chiral cholesteryl groups. our work elucidated the relationship between multiple chiral sources and CPL behavior, offering a systematic approach to designing chiral luminescent materials in the liquid-crystal phase with high ΦF and substantial glum values, providing a theoretical framework for potential applications in optoelectronic devices.

Synergistically controlled in situ growth of silver nanoparticles leading to organization of anisotropic liquid crystalline medium

ABSTRACT An in-depth macroscopic and microscopic investigation is carried out regarding understanding phase ordering and organisation of nematic phase of a room temperature nematic liquid crystal (NLC) MBBA (N-(4-methoxybenzylidene)-4-butylaniline) in the presence of silver nanoparticles (AgNPs) which are synthesised in situ in a single step using MBBA as a template as well as a reducing and stabilising unit. A synergistic effect between anisotropic LC structure and morphologies of AgNPs is observed. The LC-AgNP composite exhibits better thermal stability and phase ordering compared to its neat LC counterpart as indicated by combined study of optical polarization microscopy (OPM) and differential scanning calorimetry (DSC). While OPM study exhibits emergence of smectic mesophase in LC-AgNP composites, DSC manifests significant enhancement in the isotropic temperature and associated enthalpy as well as a change in the kinetic behaviour in LC-AgNP composites compared to neat LC. Also, an alternation in the electronic properties of LC-AgNP composites compared to neat LC is recognised. Such ordering at the macroscopic scale is well supported by our microscopic observations through spectroscopic studies such as Fourier transform infrared (FTIR) and X-ray diffraction (XRD) which provides valuable insights regarding understanding the organisation process more closely.

Synthesis and properties of chiral liquid crystal copolymers with tunable circularly polarized luminescence

Chiral liquid crystals have received widespread attention due to their unique advantages in improving circularly polarized luminescence (CPL) properties. However, how to achieve the emission and modulation of CPL for chiral liquid crystals within intrinsic polymer-based materials through a simple strategy remains a challenge. This article proposes a simple and feasible method to synthesize CPL chiral liquid crystals and manipulate their properties by copolymerizing chiral liquid crystal monomer with luminescent monomer. A series of intrinsic chiral luminescent liquid crystal copolymers C*(x)-Py(y) with tunable CPL performance were synthesized by copolymerizing chiral liquid crystal monomer MA6C* with pyrene-based luminescent monomer MC6Py in varying ratios. The effective control of the chiral liquid crystal phase structure and CPL performance of the copolymers C*(x)-Py(y) can be achieved by altering the composition of copolymers. In the copolymers, the CPL signal is generated due to the helix induction of pyrene chromophores by the chiral liquid crystals, and the CPL signal can be inverted and amplified by the unique selective reflection properties of chiral liquid crystals. For copolymer C*(0.75)-Py(0.25), the luminescence dissymmetry factor value and solid-state fluorescence quantum yield can reach −0.052 and 43.12%, respectively.

Multifaceted regulation of chiroptical properties and self‐assembly behaviors of chiral fluorescent polymers

AbstractThe multifaceted regulation of the chiroptical properties and self‐assembly behaviors of chiral fluorescent polymers is of great significance yet remains challenging to achieve. Herein, a series of novel salen‐based chiral fluorescent polymers with aggregation‐induced emission and varied substitution manners were facilely and efficiently synthesized. Multiple factors were systematically investigated on the chiroptical properties and self‐assembly performance of these polymers, which include molecular structures, solvent environments, metal coordination, and liquid crystal (LC) assemblies. Sutle change in the solvent composition can lead to diverse assembly morphologies of all these chiral polymers, from single‐handed helical fibers, helical toroids or loops, to spherical structures, consequently leading to an aggregation‐reduced circular dichroism (CD) phenomenon. The polymers bearing salen units show highly selective and reversible coordination with Zn2+ and can also induce multiple responses in the absorption, luminescence, CD, and circularly polarized luminescence (CPL) of these chiral fluorescent polymers via a coordination‐ and dissociation‐initiated self‐assembly tuning. Furthermore, a small amount of the chiral fluorescent polymer in can induce achiral nematic 4‐cyano‐4′‐n‐pentylbiphenyl (5CB) to form ordered chiral nematic LC phase with significant improvement in their CD and CPL signal. The absolute absorption and luminescent dissymmetry factors of the resulting supramolecular assemblies can reach the order of 10−1.

A novel single-sided dual-period liquid crystal phase grating with high phase difference and fast-response

The liquid crystal (LC) phase grating is highly sought-after in a myriad of applications, ranging from telecommunications to sensing technologies. However, achieving both rapid response times and high phase differences simultaneously remains a formidable challenge. Here, a novel single-sided dual-period LC phase grating structure with high phase difference and fast-response is proposed. The grating's substrate is comprised of a composite electrode, incorporating strip electrodes and a common electrode. By applying varied voltages across different electrode modules, distinct periods and diffraction angles are attained. Simulation results indicate that this approach yields phase differences of 1.61π for large-period LC phase grating and 1.17π for small-period ones. Moreover, the measured rise and decay time for the former is 8.15 ms and 4.10 ms, and for the latter is 8.84 ms and 4.12 ms, respectively. The proposed LC phase grating, with its simplicity and ease of operation, holds substantial potential for application across a broad spectrum of fields, highlighting its considerable room for development.

Thermotropic "Plumber's Nightmare"-A Tight Liquid Organic Double Framework.

Gyroid, double diamond and the body-centred "Plumber's nightmare" are the three most common bicontinuous cubic phases in lyotropic liquid crystals and block copolymers. While the first two are also present in solvent-free thermotropics, the latter had never been found. Containing six-fold junctions, it was unlikely to form in the more common phases with rod-like cores normal to the network columns, where a maximum of four branches can join at a junction. The solution has therefore been sought in side-branched mesogens that lie in axial bundles joined at their ends by flexible "hinges". But for the tightly packed double framework, geometric models predicted that the side-chains should be very short. The true Plumber's nightmare reported here, using fluorescent dithienofluorenone rod-like mesogen, has been achieved with, indeed, no side chains at all, but with 6 flexible end-chains. Such molecules normally form columnar phases, but the key to converting a complex helical column-forming mesogen into a framework-forming one was the addition of just one methyl group to each pendant chain. A geometry-based explanation is given.

Design of a Ka‐band low‐cost microstrip line phase shifter and a sum‐difference beam antenna based on liquid crystal technology

AbstractThis letter presents a Ka‐band low‐cost microstrip line phase shifter based on liquid crystal (LC) technology. Furthermore, a sum‐difference beamforming antenna array based on the LC phase shifter is designed. The phase shifter is composed of two coaxial connectors, a metal base, an intermediate dielectric layer, a gradient metal sheet and a top glass layer. The simulated results show that a nearly 360° phase shift coverage can be achieved with the effective permittivity of LC varying from 2.5 to 3.5. The sum‐difference beam antenna array is composed of a circulator, a sum‐difference network, a one‐to‐eight power‐division network, eight liquid crystal phase shifters, and a serious fed antenna array. The simulation results show that the antenna array can achieve sum‐difference beam scanning range of ±30°. A prototype of LC phase shifter is fabricated and tested. The results show that the designed LC phase shifter can achieve a 360° phase coverage by applying a direct current (DC) voltage ranging from 0 to 12 V. Compared to traditional phase shifters, the proposed design offers a simple structure at a lower cost. When applied in the design of a sum‐difference beam antenna array, it can reduce the producing cost and enable integrated design.

Quarter-wave Pancharatnam-Berry phase gradient liquid crystal-enabled dual-polarization optical edge detection.

Here, we present a novel, to the best of our knowledge, optical edge detection scheme that can be operated in both linear and circular polarization modes, leveraging an optical spatial differentiator constructed by quarter-wave Pancharatnam-Berry (P-B) phase gradient element. After explaining the theoretical mechanism, we utilize a quarter-wave P-B phase liquid crystal polarization grating to validate the dual-polarization optical edge detection capability. We demonstrate that the orientation of linear polarization and the spin of circular polarization dictate the transition between edge and bright-field images. Besides, the linear and circular polarization modes exhibit broadband and monochromatic responsive properties, respectively. This mechanism, dependent on wavelength and polarization, holds promise for applications in color image processing, chiral sensing imaging, and polarization-entangled quantum imaging.

Helical Hybrid Nanostructure Based on Chiral M13 Bacteriophage via Evaporation-Induced Three-Dimensional Process.

The use of naturally sourced organic materials with chirality, such as the M13 bacteriophage, holds intriguing implications, especially in the field of nanotechnology. The chirality properties of bacteriophages have been demonstrated through numerous studies, particularly in the analysis of liquid crystal phase transitions, developing specific applications. However, exploring the utilization of the M13 bacteriophage as a template for creating chiral nanostructures for optics and sensor applications comes with significant challenges. In this study, the chirality of the M13 bacteriophage was leveraged as a valuable tool for generating helical hybrid structures by combining it with nanoparticles through an evaporation-induced three-dimensional (3D) printing process. Utilizing on the self-assembly property of the M13 bacteriophage, metal nanoparticles were organized into a helical chain under the influence of the M13 bacteriophage at the meniscus interface. External parameters, including nanoparticle shape, the ratio between the bacteriophage and nanoparticles, and pulling speed, were demonstrated as crucial factors affecting the fabrication of helical nanostructures. This study aimed to explore the potential of chiral nanostructure fabrication by utilizing the chirality of the M13 bacteriophage and manipulating external parameters to control the properties of the resulting hybrid structures.

Emergence of cellular nematic order is a conserved feature of gastrulation in animal embryos.

Cells undergo dramatic changes in morphology during embryogenesis, yet how these changes affect the formation of ordered tissues remains elusive. Here we find that the emergence of a nematic liquid crystal phase occurs in cells during gastrulation in the development of embryos of fish, frogs, and fruit flies. Moreover, the spatial correlations in all three organisms are long-ranged and follow a similar power-law decay with less than unity for the nematic order parameter, suggesting a common underlying physical mechanism unifies events in these distantly related species. All three species exhibit similar propagation of the nematic phase, reminiscent of nucleation and growth phenomena. Finally, we use a theoretical model along with disruptions of cell adhesion and cell specification to characterize the minimal features required for formation of the nematic phase. Our results provide a framework for understanding a potentially universal features of metazoan embryogenesis and shed light on the advent of ordered structures during animal development.

Dielectric anisotropy in self-assembling MXene-based lyotropic nematic compounds

The formation of a lyotropic liquid crystal phase at the level of MXene-based aqueous dispersions due to the self-assembling capacity of these two-dimensional (2D) materials has been previously successfully reported. However, the influence of electrical external factors has been less studied in spite of the fact that understanding the electrical behaviour of 2D-based liquid crystal compounds is vital for fostering the development of new innovative applications. Consequently, within this paper, we report an in-depth evaluation of the dielectric properties of liquid crystalline phases in Ti3C2 MXene aqueous dispersions. The dependence on the low voltage of planar ε⊥′ to homeotropic ε∥′ orientational transition is emphasized and discussed, while the influence of the electric field frequency at the level of dielectric anisotropy is assessed in respect to various concentrations of MXene flakes within the same 2D-based compounds. Nonetheless, dielectric spectroscopy highlights the biphasic nature (containing both nematic and isotropic phases) of the studied aqueous Ti3C2 MXene inks visible up to 20% MXene. Above this concentration, the existence of a pure nematic phase in the dispersion of highMXene concentration (>20 wt%) was detected based on the evaluation of dielectric permittivity against various voltage values.

Phase behavior and rheology of the sucrose laurate/sorbitan mono-laurate (Span 20)/water pseudo-ternary system

In order to develop a lamellar liquid crystal system consisting of temperature-insensitive and mild non-ionic surfactants, we construct the phase diagram of sucrose laurate (L1695)/sorbitan monolaurate (Span 20)/water pseudo-ternary systems at 25 ℃ based on the direct visual inspection and polarized microscopy. In contrast to the phase diagrams of polyoxyethylene alkyl ethers and co-surfactant mixtures reported in relevant studies, the single-phase region of the liquid crystalline phase in sucrose laurate (L1695)/sorbitan monolaurate (Span 20)/water pseudo-ternary systems is shown to be narrower. Moreover, the liquid crystal phase behaviors of the sucrose laurate/sorbitan mono-laurate (Span 20)/water pseudo-ternary systems are examined in depth applying cryo-SEM, X-ray scattering measurements, rheological test and low field NMR experiments. In the abovementioned aqueous systems with a L1695 to Span 20 mass ratio (between 53.9: 46.1 and 43.3:56.7), sucrose mono-laurate combines with a certain number of sorbitan monolaurate molecules to form a single lamellar liquid crystalline phase. Furthermore, the present experimental results as well as their analysis could give the quantitative playground for the interaction between sugar-based surfactants in aqueous system, which has rarely been investigated compared with the phase behavior of polyoxyethylene alkyl ethers in aqueous solution.

Imaging tunable Luttinger liquid systems in van der Waals heterostructures.

One-dimensional (1D) interacting electrons are often described as a Luttinger liquid1-4 having properties that are intrinsically different from those of Fermi liquids in higher dimensions5,6. In materials systems, 1D electrons exhibit exotic quantum phenomena that can be tuned by both intra- and inter-1D-chain electronic interactions, but their experimental characterization can be challenging. Here we demonstrate that layer-stacking domain walls (DWs) in van der Waals heterostructures form a broadly tunable Luttinger liquid system, including both isolated and coupled arrays. We have imaged the evolution of DW Luttinger liquids under different interaction regimes tuned by electron density using scanning tunnelling microscopy. Single DWs at low carrier density are highly susceptible to Wigner crystallization consistent with a spin-incoherent Luttinger liquid, whereas at intermediate densities dimerized Wigner crystals form because of an enhanced magneto-elastic coupling. Periodic arrays of DWs exhibit an interplay between intra- and inter-chain interactions that gives rise to new quantum phases. At low electron densities, inter-chain interactions are dominant and induce a 2D electron crystal composed of phased-locked 1D Wigner crystal in a staggered configuration. Increased electron density causes intra-chain fluctuation potentials to dominate, leading to an electronic smectic liquid crystal phase in which electrons are ordered with algebraical correlation decay along the chain direction but disordered between chains. Our work shows that layer-stacking DWs in 2D heterostructures provides opportunities to explore Luttinger liquid physics.

Photoinduced Phase Transitions of Imine-Based Liquid Crystal Dimers with Twist-Bend Nematic Phases.

Photoisomerizable molecules in liquid crystals (LCs) allow for photoinduced phase transitions, facilitating applications in a wide variety of photoresponsive materials. In contrast to the widely investigated azobenzene structure, research on the photoinduced phase-transition behavior of imine-based LCs is considerably limited. We herein report the thermal and photoinduced phase-transition behaviors of photoisomerizable imine-based LC dimers with twist-bend nematic (NTB) phases. We synthesize two homologous series of ester- and thioether-linked N-(4-cyanobenzylidene)aniline-based bent-shaped LC dimers with an even number of carbon atoms (n = 2, 4, 6, 8, and 10) in the central alkylene spacers, namely, CBCOOnSBA(CN) and CBOCOnSBA(CN), possessing oppositely directed ester linkages, C=OO and OC=O, respectively. Their thermal phase-transition behavior is examined using polarizing optical microscopy and differential scanning calorimetry. All dimers form a monotropic NTB phase below the temperature of the conventional nematic (N) phase upon cooling. Remarkably, the NTB phases of CBCOOnSBA(CN) (n = 2, 4, 6, and 8) and CBOCOnSBA(CN) (n = 6 and 8) supercool to room temperature and vitrify without crystallization. In addition, the phase-transition temperatures and entropy changes of CBCOOnSBA(CN) are lower than those of CBOCOnSBA(CN) at the same n. Under UV light irradiation, the NTB and N phases transition to the N and isotropic phases, respectively, and reversibly return to their initial LC phases when the UV light is turned off.

An overview on cubic liquid crystalline nanoparticles-trig lipid drug delivery system

This type of complex structure allows them greater drug loading ability, because of increased surface area and cuboidal structures, they have simple method of preparation and have ability to encapsulate hydrophilic, hydrophobic and amphiphilic substances. Cubosomes increases the solubility of poorly soluble drugs. Cubosomal dispersions are bioadhesive and biocompatible in nature. These are versatile systems, administered by different ways such as oral, perctuneous and parental routes. Cubosomes have broad vast applications in many areas and are characterized by various parameters consequently cubosomes are in move forward of awareness by pharmaceutical development division. Cubosomes, sometimes referred to as bicontinuous cubic phase liquid crystals, are spherical, quadruple nanoparticles with an interior cubic lattice mostly composed of certain amphiphilic lipids in a particular proportion. Cubosomes often arise when a solid-like phase is dispersed into smaller particles after a surfactant or polar lipid is hydrated to form a cubic phase. With distinct qualities of practical interest, they exhibit solid like rheology. They are thermodynamically stable, self-assembling drug delivery devices. Water and lipid bicontinuous domains give cubosomes their carvenous structure. Three-dimensional bilayers are formed by tightly twisted honeycomb arrangements.

Difluorinated tolane-based photoluminescent liquid crystals with imidazolium salt-terminated flexible chains: Thermophysical and photophysical properties

Photoluminescent liquid crystal (PLLC) molecules have attracted significant interest because they exhibit both photoluminescent (PL) and liquid crystal (LC) properties within a single-composition molecular system. In the quest to develop PLLC molecules, researchers have explored ionic compounds incorporating ionic moieties in flexible chains or mesogenic structures. Notable examples include disk-shaped columnar PLLCs and smectic (Sm) PLLCs, which exhibit distinct layers of ionic moieties, counterions, and luminescent mesogens. Ionic LC molecules exhibiting the Sm phase at low temperatures and whose phase transition temperatures can be modulated by tuning the ionic moiety show promise as PLLCs. However, reports on Sm PLLC molecules remain scarce. Based on previous findings that difluorinated tolanes can emit fluorescence in the crystalline (Cr) state, we explored their potential as luminescent mesogens for the development of efficient Sm PLLC compounds. In this study, we designed a rod-shaped compound featuring a difluorinated tolane skeleton as a luminescent mesogen, a decyleneoxy chain for stabilizing the LC phase, and an imidazolium ion as an ionic moiety at the chain end to induce the smectic A (SmA) phase. Upon investigating their thermophysical properties, all compounds demonstrated thermotropic LC attributes and contained a SmA phase. Notably, the melting temperature decreased with increasing anion volume. Photophysical property evaluation revealed that the compounds displayed blue photoluminescence in both dilute solutions and Cr states, with no counteranion-dependent variations in photoluminescence observed in the solution. However, the photoluminescence behavior in the Cr-state specimens varies with different counteranions, demonstrating an increased photoluminescence wavelength with increasing anion volume. Furthermore, the Cr ⇄ LC phase transition altered the photoluminescence behavior, highlighting the potential of our molecular design strategy for developing temperature-responsive PL materials. These findings provide valuable insights for designing new PLLC molecules that can serve as effective fluorescent sensors across a range of temperatures, including room temperature.