Asymmetric Liquid Research Articles

Blue Phase III from Bent-Core Liquid Crystals: Unveiling Thermal Stability & Unique Traits - A Comprehensive Review.

This review article mainly delves into the comprehensive development, thermal stabilization, characteristics, and applications of Blue Phase III (BPIII) derived from non-calamitic, mainly T-shaped and bent-core liquid crystals (BCLC). The discussion begins with discovering and characterizing various liquid crystal (LC) phases of BCLCs, emphasizing the significance of the nematic (N) phase in three and four-ring BCLCs. Following this, the focus shifts to the stabilization, properties, and potential applications of BPIII, particularly those derived from non-conventionalliquid crystals. The review highlights the exceptional electro-optical (E-O) properties of BPIII, including high Kerr constants and distinct phase transitions. Studies reveal the impact of chirality on thermal behavior, microscopic observations, and the influence of molecular structures on mesophase formation. Investigations into asymmetrical chiral liquid crystal diads and hydrogen-bonded complexes underscore the importance of molecular design in expanding BPIII ranges. Furthermore, achiral unsymmetrical BCLC designs reveal significant insights into the interplay between molecular structure, phase transitions, and E-O behavior.Additionally, the structural transformation and E-O properties of highly polar BCLCs are examined to stabilize BPIII at room temperature, achieving notable Kerr constants and low voltage requirements. These collective studies provide a thorough understanding of BPIII and its promising applications in materials science and technology.

Development of an asymmetric cellulose acetate-ionic liquid P6,6,6,14[PHOS] gel membrane for the perstraction of succinic acid from a model fermentation solution of yarrovia lipolytica

This study introduces a novel approach to separate succinic acid (SA) from fermentation mixtures using an asymmetric membrane based on the gelation of the ionic liquid [P6,6,6,14][PHOS] coated with two layers of cellulose acetate. The membrane was designed to explore the synergistic effect of polymer-ionic liquid interfaces according to the solution-diffusion theory. The gelation of the ionic liquid was achieved using 12-hydroxystearic acid at a concentration of 1.5%, allowing the use of ionic liquid gels as new materials for the generation of membranes. The perstraction performance of the membrane was evaluated over 5 h at two different temperatures (25°C and 37°C), with an initial feed solution concentration of 50 kg m−3 for SA and glycerol and pure water as a receiving phase., Several flow rates and phase-volume ratios were studied anda mass transfer model based on the resistance-in-series theory was assessed to understand the behavior of each mass transfer stage considering the distribution in each interphase. Interestingly, optimal perstraction results were obtained at 37°C, with an average transmembrane flux of 0.22 kg m-2h−1 for SA, an extraction percentage of 43.1% for SA and 0.7% for glycerol, and a SA/glycerol selectivity of 54.98. Besides presenting a novel composite membrane, this study reports pioneering perstraction outcomes, highlighting its potential as an innovative SA separation strategy and structured new materials for selective extractions.

Asymmetric dual-core liquid crystal channel-based tunable mode converter

In this work, a higher order-to-fundamental mode converter is reported and analyzed based on an asymmetric dual channel waveguide (ADC-WG) on silicon. In the reported structure, one of the two waveguides is infiltrated with nematic liquid crystal (NLC) material to add temperature tunability while the other one is a solid BK7 waveguide. The modal characteristics are obtained using the full vectorial finite difference method (FVFDM). In addition, the structural parameters and optical characteristics of the employed materials are investigated to achieve good wavelength selectivity with a short device length (LD). Thus, a compact mode converter that can work at different wavelengths including the telecommunication wavelength i.e., 1.55 μm with LD ~ 482.31 μm and a low crosstalk of − 19.86 dB is presented. To prove the thermal tunability of the suggested mode converter, its operation is tested through a temperature range between 20 and 35 °C and the results show that the mode conversion process is achieved at each temperature with different phase matching wavelengths (λPMW) but with quite similar coupling length (LC). The proposed device can therefore be effectively utilized in integrated photonic circuits.

Investigating the coupling between transport and reaction within a catalyst pellet using operando magnetic resonance spectroscopic imaging

In heterogeneous catalysis, the distribution of reactant and product species within a catalyst pellet are of central importance to the catalyst performance, and ultimately to the overall conversion and selectivity achieved in commercial-scale reactors. Despite this importance, fundamental understanding of pellet scale behaviour at operando conditions is limited due to the coupled, multi-scale nature of the underlying transport processes, and the limited techniques capable of mapping the intra-pellet composition at industrially relevant length scales. Here, we demonstrate the coupling between transport and reaction at the pellet scale by using operando magnetic resonance spectroscopic imaging (MRSI) to map the liquid composition within Pd/γ-Al2O3 catalyst pellets at an isotropic in-plane spatial resolution of 86 µm during a styrene hydrogenation reaction. The results reveal that asymmetric liquid wetting at the pellet surface, typical of that occurring in trickle-bed reactors, causes significant composition heterogeneity across a catalyst pellet. Due to the wetting inhomogeneity, commonly used 1D reaction-diffusion models are inadequate for describing the observed composition heterogeneity across the pellet. The results reported here provide unique experimental insight into the coupling between transport and reaction at the pellet scale within an operating reactor.

Synthesis, characterization, mesogenic properties, and DFT studies of unsymmetrical liquid crystalline dimers of biphenyl

ABSTRACT A series of asymmetrical liquid crystal dimers (E)-4((4(n([1,1’-biphenyl]-4-yloxy)alkoxy)phenyl) diazenyl)benzonitrile (BpnCN) were synthesized, consisting of two distinct rigid cores: 4-cyanoazobenzene and biphenyl units. Characterization was accomplished through various spectroscopic techniques. The mesomorphic properties were explored via polarizing optical microscopy and differential scanning calorimetry. UV–Visible spectroscopy assessed the photophysical properties. The presence of an even number of atoms in the flexible spacer resulted in linear molecular shapes for Bp4CN and Bp6CN, while Bp3CN and Bp5CN showed nonlinearity, explaining their non-mesomorphic properties. Computational studies showed a clear correlation between theoretical and experimental wave numbers. The enhanced stability of the mesophase in Bp4CN and Bp6CN was attributed to their higher aspect ratios, promoting ordered structures within the material. UV–visible spectroscopy of dimer Bp4CN revealed absorption bands at 445 nm (n–π* transitions) and 365 nm (π–π* transitions), with photoisomerization observed under UV exposure, reaching a photostationary state in 2.5 min and reversible isomerization back to the trans form in approximately 2.3 h. Notably, even in the absence of substitutions on the biphenyl core, the dimers in our present series demonstrated an enantiotropic nematic mesophase.

Asymmetrical liquid crystals synthesis for effective sensing: Fluorescence investigations

Currently, a new set of asymmetrical dimeric molecules with a Schiff-base at one end and a chalcone alkali substitution by di-ether are made and their liquid crystal and fluorescence properties are investigated. The proposed chemical structure was confirmed by routine analytical methods using FT-IR and NMR spectroscopy. Additionally, polarized optical microscopy (POM); was used to assess the pointed compounds' liquid crystalline characteristics, while differential scanning calorimetry (DSC); was employed to confirm the compounds' transitions. The results report the length of the alkali chain at one end of the molecule is critical to the creation of the mesophase type. Compounds with medium-length chains exhibit nematic mesophases with moderate transition temperatures. The fluorescence of compounds was analyzed, with blue-emitting results indicating the presence of blue-light-emitting features. The 10a had higher ɛ; as well as red-shifted λmax; and Fmax; compared to the others and has blue light emission properties. Eventually; the expanding range of possible uses to include OLED material and fluorescent probes for sensing applications.

Revealing the causes of degradation of an asymmetric ionic liquid supercapacitor with a composite polyaniline/carbon electrode

The extended window of electrochemical stability of ionic liquids and the high specific capacitance values of activated carbon (AC)/conductive polymer (polyaniline, Pani) composite materials are promising approaches to improve the performance of supercapacitors (SC).In this work, we studied the stability of an asymmetric AC//Pani-C cell with 1 M solution of 1-butyl-3-methylimidazolium tetrafluoroborate (BMIMBF4) in acetonitrile as an electrolyte. Pani-C (56 wt% of Pani) composite was prepared by oxidative polymerization of aniline in the presence of high surface area AC (SBET = 2300 m2‧g−1). Fourier-transform infrared spectroscopy, X-ray photoelectron spectroscopy, transmission and scanning electron microscopies data confirmed the formation of Pani-C composite. Combination of cyclic voltammetry, galvanostatic charge/discharge method, and electrochemical impedance spectroscopy in 2- and 3-electrode cell configurations gave information about anodic (1 V vs. Ti) and cathodic (−1.8 V vs. Ti) potential limits of electrochemical stability, and potential of zero charge of Pani-C and AC.From these data, optimal mass ratio of Pani-C and AC electrodes was obtained for asymmetric SC assembly. It was found that after 500 charge/discharge cycles, the capacitance of the asymmetric AC//Pani-C SC decreased by 15% from 46.8 to 39.9 F·g−1 as a result of Pani-C degradation. The specific capacitance of AC remained virtually unchanged (decreased from 144 to 141 F·g−1), while that of Pani-C decreased by 8.7% from 230 to 210 F·g−1. Electrochemical measurements showed that degradation is accompanied by an increase in the working potential window of Pani-C (from 0.85 V to 0.97 V) and a shift in Emin…Emax working potentials from 0.15 … 1 to 0.52 … 1.49 V vs. Ti in the beginning and in the end of stability test, respectively. The last region is related to the potential for non-conductive pernigraniline formation (1.3 V vs. Ti). It was shown that the main reason of AC//Pani-C SC capacitance decay is a gradual increase in the operating potential window with a constantly shifts towards anodic values of positive Pani-C electrode, which resulted in accumulation of nonconductive polymer form that does not participate in charge accumulation.

Proton-decoupled deuterium NMR study of an asymmetric liquid crystal dimer having two nematic phases.

Proton-decoupled deuterium NMR spectra were obtained for an asymmetric liquid crystal dimer 1-(4-cyanobiphenyl-4'-yloxy)-6-(4-cyanobiphenyl-4'-yl)hexane (CB6OCB) containing a single -CD_{2}- group. The sample has two nematic liquid crystal phases: a twist-bend nematic, N_{TB}, at the lowest temperature followed by a uniaxial nematic, N_{U}, on increasing the temperature. Proton decoupling reduces the linewidths of the peaks in the deuterium spectrum from kHz to ∼100Hz, enabling quadrupolar splittings, Δν, to be obtained with enhanced precision as well as the dipolar coupling between deuterium nuclei within the CD_{2} group, hence enhancing the information content.

Dielectric Study of Liquid Crystal Dimers: Probing the Orientational Order and Molecular Interactions in Nematic and Twist-Bend Nematic Phases.

Dielectric spectroscopy in frequencies that range from 10 Hz to 1 GHz has been used to study the molecular orientational dynamics of the two types of dimers that form the twist-bend nematic phase over a wide range of temperatures for both nematic and twist-bend nematic phases. The symmetrical and asymmetrical liquid crystal dimers with the cyanobiphenyl mesogenic groups were investigated. The results were analyzed within the framework of the molecular theory of dielectric permittivity for nematogens. The two molecular processes can be assigned to the reorientation of the monomeric unit: the high frequency one to the precessional rotation of the longitudinal components of the cyanobiphenyl groups (CN) and the second (low frequency) to the end-over-end rotation of the CN dipole around the short molecular axis. The precession mode, which is determined by the local order and is almost unaffected by the phase transition from the nematic to the twist-bend phase, while the end-over-end rotation clearly slowed down at the transition, as it is affected by the growth of the intermolecular interactions. The latter corresponds well to the fact revealed by IR spectroscopy about the longitudinal correlation of the molecular dipoles.

Bionic Jaw-Like Micro One-Way Valve for Rapid and Long-Distance Water Droplet Unidirectional Spreading.

A surface with asymmetric microstructures for self-driven directional spreading of liquid has attracted keen interest from researchers in recent years for its great application prospects. Inspired by the jaws of tiny insects, such as ants, a surface textured with novel jaw-like microstructures as micro one-way valves is reported. These microstructures are almost two-dimensional, thus being simple and easy to fabricate. Whereas surfaces with such jaw-like micro one-way valves exhibit amazing rapid and long-distance water droplet unidirectional spreading behaviors. The maximum forward-backward distance ratio of water droplets on surfaces with the optimized microstructures is about 14.5, almost twice those of previous research. The capillary attraction at the location of the mouth of the jaws and the pinning effect brought by the sharp edge of the jaws for the precursor film are analyzed and deduced as the main mechanisms. The findings open a promising avenue for 2D asymmetric microstructure design and effective self-driven liquid unidirectional spreading.

Leaning induced layer undulated tilted smectic phase of asymmetric bent-core liquid crystals.

We report the synthesis and experimental studies on the liquid crystalline phase of a homologous series of compounds comprised of strongly asymmetric bent-core banana shaped molecules. Our x-ray diffraction studies clearly indicate that the compounds exhibit a frustrated tilted smectic phase with layer undulated structure. The low value of the dielectric constant as well as switching current measurements indicate the absence of polarization in this layer undulated phase. In spite of the absence of polarization, a planar aligned sample can be transformed irreversibly to a higher birefringent texture on the application of a high electric field. The zero field texture can only be retrieved by heating the sample to the isotropic phase and cooling it subsequently to the mesophase. We propose a double tilted smectic structure having layer undulation to account for the experimental observations with the layer undulation arising due to the leaning of the molecules in the layer.

Improvement of thermal conductivity of novel asymmetric dimeric coumarin liquid crystal by doping with boron nitride and aluminium oxide nanoparticles

Coumarin compound-derived dimeric molecules are synthesized and characterized for enhancing the thermal conductivity of liquid crystals. The chemical structures are characterized and confirmed by standard spectroscopic techniques such as FT-IR, 1D and 2D NMR, and elemental analysis. Mesophases were analysed and characterized by the combination of POM, DSC, and X-ray analysis techniques. Most compounds show SmA mesophases upon heating and cooling run except compounds 5b and 5d which are non-mesogenic in the cooling cycle. Mixing coumarin compounds with boron nitride nanosheets (BNNS) and aluminium oxide nanoparticles (Al2O3) dramatically increased the thermal conduction of the liquid crystals (LCs). Doping with 15 wt % of Al2O3 increased the thermal conductivity of LCs from 0.26 W/m K to 0.51 W/m K. While mixing LCs with 35 wt% BNNS increased the thermal conductivity to 0.91 W/m K. The outstanding thermal conductivity of 1.6 W/m K and the specific TCE (per 1 wt% of nanofillers) of ∼12.5% were obtained by mixing LCs with a combination of 15 wt% Al2O3 and 35 wt% BNNS. In addition, the thermal stability of LCs was intensified when doping with nanofillers due to occupying the free volumes between molecules and reducing the overall mobility of the compound. The obtained thermal performance from the prepared LCs nanocomposites of this work illustrated vast potential in specific electronic applications such as photonic systems and solar energy collectors.

DNMR measurements of an asymmetric odd liquid crystal dimer: determination of the intramolecular angle and the degree of order of the two rigid cores.

In this work, we present a Deuteron Nuclear Magnetic Resonance (DNMR) study of the non-symmetric odd liquid crystal dimer α-(4-cyanobiphenyl-4'-yloxy)-ω-(1-pyrenimine-benzylidene-4'-oxy) heptane (CBO7O.Py), formed by a pro-mesogenic cyanobiphenyl unit and a bulky pyrene-containing unit, linked via alkoxy flexible chain. We have synthesized two partially deuterated samples: one with the deuterium atoms in the cyanobiphenyl moiety (dCBO7O.Py) and the other one with the deuterium atoms in the pyrenimine-benzylidene unit (CBO7O.dPy). We have performed angular distribution analysis in the SmA glassy state, obtaining the degree of order of both rigid cores and an estimation of the internal molecular angle between both structures. With the results from the angular study, we have been able to determine the degree of order of both rigid units in either the N phase and the SmA phase, far enough from the glass transition. Both rigid cores have the same degree of order close to the nematic-isotropic phase transition, but as the compound is cooled down, the degree of order of the cyanobiphenyl moiety is clearly higher than that of the pyrene-containing unit. The critical behaviour of the order parameter of the pyrene-containing moiety is consistent with the fact that, for CBO7O.Py, the N-I phase transition is tricritical, which seems to indicate that the uniaxial order parameter of the dimer is dominated by the degree of order of the pyrene-containing core.

Fragmentation of asymmetric liquid filaments and formation of satellite droplets in a microchannel

This study analyzes the breakup dynamic of fluid filament in a T-junction microchannel, including droplet stretching process, liquid filament retraction process and breakup process. The liquid filaments spontaneously evolve into droplets or break into multiple satellite droplets, which can be considered as the result of the competition between the retraction and elongation mechanisms of the liquid filaments. There is an obvious local interfacial tension difference during the shrinkage of the droplet filament, which promotes the discharge of the internal fluid, and then the filament is pinched, resulting in the formation of satellite droplets. On the basis of symmetrical filament pinch-off, and the fully considering of the influence of viscosity and the crossing flow, the elongation and retraction mechanism of droplet filaments in the microchannel are proposed. The study reveals the breakup of asymmetric liquid filaments in a microchannel and the formation of satellite droplets, which provides references for the manipulation of satellite droplets in a microchannel.

An experimental determination of the liquidus and a thermodynamic melt model in the CaCO3-MgCO3 binary, and modelling of carbonated mantle melting

The binary CaCO3-MgCO3 constitutes the reference model system to reconstruct the petrogenesis of carbonated rocks, and of carbonatite magmas possibly generated in the Earth's mantle. We experimentally determined the melting of aragonite and magnesite to pressures of 12 GPa, and of calcite-magnesite mixtures at 3 and 4.5 GPa, at variable Ca/(Mg + Ca) (XCa). The melting curves of aragonite, and magnesite have similar slopes, the latter melting ≈ 30 °C higher than aragonite. In the Ca-Mg binary, the minimum of the liquidus surface situates at an XCa of 0.65–0.60, at 1200 °C − 3 GPa, and 1275 °C − 4.5 GPa. Together with available data at 1 and 6 GPa, the minimum liquid composition remains approximately constant with pressure. All available experimental data are then fit by the first thermodynamic model for CaCO3-MgCO3 liquids. Surprisingly, although carbonate liquids should behave as relatively simple molten salts, the liquids display large non-ideality and a three-component, pressure dependent, asymmetric liquid solution model is required to model the liquidus surface. Attempts to use only the two end-member components fail, invariably generating a very wide magnesite-liquid loop in disagreement with the experimental evidence.The liquid model is then used to evaluate results of experimentally determined phase relationships for carbonated peridotites in CaO-MgO-SiO2-CO2 (CMS-CO2), and CaO-MgO-Al2O3-SiO2-CO2 (CMAS-CO2). Computations highlight that the liquid composition formed in a model carbonated mantle do not represent “minimum melts” but are more magnesian at high pressure. The pressure–temperature position of the solidus, as well as its dP/dT slope, including the appearance or absence of the “carbonatite ledge”, depend on bulk composition, unless truly invariant assemblages occur.

Thermal behavior, decomposition mechanism by TG/MS/FTIR technique and theoretical study of some symmetric and asymmetric bent-core liquid crystals based on 2,7-dihydroxynaphthalene

Thermal behavior, decomposition mechanism by TG/MS/FTIR technique and theoretical study of some symmetric and asymmetric bent-core liquid crystals based on 2,7-dihydroxynaphthalene

High-Efficiency Directional Ejection of Coalesced Drops on a Circular Groove.

Coalescence-induced drop jumping has received significant attention in the past decade. However, its application remains challenging as a result of the low energy conversion efficiency and uncontrollable drop jumping direction. In this work, we report the high-efficiency coalescence-induced drop jumping with tunable jumping direction via rationally designed millimeter-sized circular grooves. By increasing the surface-droplet impact site area and restricting the oscillatory deformation, the energy conversion efficiency of the jumping droplet reaches 43.5%, 600% as high as the conventional superhydrophobic surfaces. The droplet jumping direction can be tuned from 90° to 60° by varying the principal curvature of the circular groove, while the energy conversion efficiency remains unchanged. We show through theoretical analysis and numerical simulations that the directional jumping mainly originates from reallocation of droplet momentum enabled by the asymmetric liquid bridge impact. Our study demonstrates a simple yet effective method for fast, efficient, and directional droplet removal, which warrants promising applications in jumping droplet condensation, water harvesting, anti-icing, and self-cleaning.

Alkylthio-based asymmetric liquid crystals: unravelling the substituent effects and intercalated cybotactic nematic and smectic phases

A homologous series of alkylthio- and alkoxy-based asymmetric calamitic liquid crystal (LC) molecules was developed. The effects of alkylthio groups on the phase transition properties and unexpected intercalated LC phase structures were studied.

Thermodynamic modelling of the ternary Bi-Ga-Te system for potential application in thermoelectric materials

Thermoelectric materials have drawn widespread attention because they can enable the direct conversion between electric and thermal energy. Over the years, different materials such as skutterudites, clathrates, intermetallic alloys, eutectic alloys, chalcogenides have been explored for Thermoelectric (TE) applications. Amongst the eutectic alloys, the Bi-Ga-Te system exhibits promising potential as a TE material. Accordingly, in this study, we performed the thermodynamic optimization and critical evaluation of binary Bi–Ga, Bi–Te, Ga–Te, and ternary Bi-Ga-Te systems using the CALPHAD method. It is observed that the Ga–Te system shows asymmetric liquid solution properties with strong negative enthalpy of mixing, whereas the Bi–Te liquid exhibits the symmetric regular solution behavior. Moreover, the Bi–Ga liquid solution has a positive enthalpy of mixing. Therefore, Modified Quasichemical Model (MQM) using pair approximation was utilized to describe the diversified thermodynamic properties of liquid solution in sub-binaries by taking into account the Short-Range Ordering (SRO). By merging the binary optimization results with a proper interpolation method, the liquid solution properties and phase diagram information in the Bi-Ga-Te ternary system were also reproduced successfully without any adjustable ternary parameter. Several ternary eutectic compositions were suggested for designing TE alloy with enhanced properties using the developed database.

Chiral Polymorphic Hydrazine-based Asymmetric Liquid Crystal Trimers with Resorcinol as Linking Group.

This is the first report on chiral polymorphic hydrazine-based asymmetric liquid crystal trimers, 1-[4'-(4''-(5-Cholesteryloxy)carbonyl)butyloxy]-3-[N-benzylideneoxy-N'-(4'''-decyloxybenzylidene) hydrazine] butyloxybenzenes, and 1-[4'-(4''-(10-cholesteryloxy)carbonyl)nonyloxy]-3-[N-benzylideneoxy-N'-(4'''- decyloxybenzylidene)hydrazine]butyloxybenzenes., in which the hydrazine and cholesterol arms were connected via two flexible methylene spacers (n = 3-12 units and m = 4 or 9, respectively) to the central resorcinol core. FT-IR, 1D and 2D NMR spectroscopy, and CHN microanalysis were used to elucidate the structures of the trimers. Differential scanning calorimetry, polarizing optical microscopy and X-ray diffraction were used to study the transitional and phase properties of the trimers, which were length and spacer parity dependent. Trimers with short spacer length in the cholesteryl arm, m = 4 showed an interesting phase sequence of BP/N*-TGBA*-SmA*. The TGBA* phase was sensitive to spacer length as it was only observed in trimers with short ester linkage. For the long analogues, m = 9, characteristic visible reflection and a much simpler phase sequence with only N* and SmA* phases were observed. The X-ray diffraction measurements revealed that layer periodicities of the SmA* phase were approximately half the estimated all-trans molecular length (d/L ≈ 0.44-0.52), thus suggesting that the molecules are either strongly intercalated or bent.