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Effect of fullerenes C60 on dielectric relaxation and electric conductivity of nematic liquid crystal 4-methoxybenzylidene-4'-butylaniline (MBBA) is investigated. It is shown that the inclusion of ...

In this work, it is proposed a perturbation theory in conjunction with the Convex Peg HERSW model and an adjustable intermolecular potential. The perturbation theory developed can quantitatively predict the density–pressure–temperature experimental behavior at the isotropic–nematic phase transition of MBBA at 1 atm.

Gold nanoparticles have received widespread attention as surface-enhanced Raman scattering (SERS) detection active substrates. In this work, we used the nematic liquid crystal molecule N-(4-methoxybenzylidene)-4-butylaniline (MBBA) at room temperature to synthesize liquid crystal (LC)-Au nanoparticles in one step without adding any other reducing agents or stabilizers. Gold nanoparticles synthesized by this method have good sensitivity and stability as a SERS substrate. The nanoparticles can detect Rhodamine 6G (R6G) molecules with a concentration as low as 10−8 M, and the SERS signal does not decrease significantly in 30 days. Using this synthesis principle, we grew gold nanoparticles in a capillary in one step. We expect the proposed method to result in a highly efficient and portable SERS substrate after subsequent improvements.

The mutual influence of two mesogenic components, namely a nematic liquid crystal N-(p-methoxy-bezylidene)-butylaniline (MBBA) and a lyotropic liquid crystal poly-(phenyl-methacrylic) ester of cety...

The current research on adversarial attacks aims at a single model while the research on attacking multiple models simultaneously is still challenging. In this paper, we propose a novel black-box attack method, referred to as MBbA, which can attack multiple black-boxes at the same time. By encoding input image and its target category into an associated space, each decoder seeks the appropriate attack areas from the image through the designed loss functions, and then generates effective adversarial examples. This process realizes end-to-end adversarial example generation without involving substitute models for the black-box scenario. On the other hand, adopting the adversarial examples generated by MBbA for adversarial training, the robustness of the attacked models are greatly improved. More importantly, those adversarial examples can achieve satisfactory attack performance, even if these black-box models are trained with the adversarial examples generated by other black-box attack methods, which show good transferability. Finally, extensive experiments show that compared with other state-of-the-art methods: (1) MBbA takes the least time to obtain the most effective attack effects in multi-black-box attack scenario. Furthermore, MBbA achieves the highest attack success rates in a single black-box attack scenario; (2) the adversarial examples generated by MBbA can effectively improve the robustness of the attacked models and exhibit good transferability.

In present work, Cu:ZnO nanoparticles (NPs) used to disperse in pure nematic liquid crystal N-(4-methoxybenzylidene)-4-butylaniline (MBBA). Due to their larger dipole moment of NPs have stronger in...

We study rheology, microstructure, and response to an applied electric field (E) in suspensions of fumed alumina (Al2O3) nanoparticles in a nematic liquid crystal (NLC) made of N-(4-methoxybenzylidene)-4-butylaniline (MBBA). Fumed Al2O3/MBBA suspensions exhibit flowability with nanoparticle volume fraction (ϕ) = 0.001 and 0.007, and become solid-like gels at a nanoparticle ϕ = 0.014 and beyond. The dynamic rheology of gel-like suspensions follows the soft glass rheology (SGR) model. The effective noise temperature remains close to 1 for these Al2O3/MBBA suspensions, which serves as an indication of the presence of glassy dynamics. Further, the optical microscopy and the differential scanning calorimetry (DSC) reveal that the incorporation of fumed Al2O3 nanoparticles causes a significant depression in the nematic-isotropic phase transition temperature (TNI). The gel-like suspensions are less sensitive to pre-shear and show a large structural recovery after shear when compared to Al2O3/silicone oil suspensions. At and above a critical nanoparticle ϕ = 0.005, the suspensions exhibit a reversible nematic-isotropic phase transition under the application of E.

An open system is a system driven away from equilibrium by a source that supplies an inflow of energy and a sink to maintain an outflow. A typical example of an open system is a system close to its phase transition temperature under irradiation by a laser. This provides a steady flow of energy through a photon flux. The sink in that case is the environment to which energy is lost in the form of heat dissipation. Creation of such a thermodynamically open state suggests that we can expect generation of exotic spatio-temporal structures length-scale independent correlation maintained under the global dissipative forces provided by the surroundings. Internal long-range forces can bring in additional spatio-temporal correlations, giving rise to states with a very long lifetime, the ‘quasistationary states’ (QSS). In this communication, we report evolution of quasistationary states, in a mixture of the well-known liquid crystal (N-(4-methoxybenzylidene)-4-butylaniline, MBBA) and an iron-based room temperature ionic liquid (RTIL), namely, 1-ethyl-3-methylimidazolium tetrachloroferrate (EMIF) at the Nematic-Isotropic phase transition, when focused radiation with 532 nm wavelength from a Nd:YAG laser (200-300 mW optical power) is incident on the sample. We explain the QSS by invoking a sharp negative thermal gradient due to the laser photon flux and dipolar interactions. In our model, the dipoles are the charge transfer complexes (CTCs) formed in the RTIL by resonant laser pumping, which create an orientational ordering and balance the fluctuating force of the thermal gradient to create the QSS. In the absence of such CTCs in a mixture of MBBA and a Gallium-based RTIL (1-ethyl-3-methylimidazolium tetrachlorogallate, EMIG), the QSS was not observed.

Experimental investigations of the effects of limiting of a beam traversing a different light-scattering medium based on liquid crystals are presented. It is shown that the result of limiting of the beam at the output of the medium depends on the magnitudes of the phase delays of the singly forward scattered partial signals. Investigations of the effects of limiting has been carried out using nematic liquid crystals MBBA with carbon nanotubes (CNT) in comparison wihs a solution of the same liquid crystals doped by carbon nanodots. Liquid crystals dopped by carbon nanotubes or nanodots, located between crossed polarizers, delays external optical radiation as its power increases to a certain critical level. This can be explained by the phase changes in the LC dopped by the nanoparticles under the action of heating aimed by radiation or an applying external electromagnetic field. Observed phenomena strongly influenced by shape, size and concentration of CNT, as well as the sensitivity of the liquid crystal to the illuminating beam power rate has increased.

The ability to quantify protein-ligand interactions in an accurate and high-throughput manner is important in diverse areas of biology and medicine. Multiplex bead binding assays (MBBAs) are powerful methods that allow for simultaneous analysis of many protein-ligand interactions. Although there are a number of well-established MBBA platforms, there are few platforms suitable for research and development that offer rapid experimentation at low costs and without the need for specialized reagents or instruments dedicated for MBBA. Here, we describe a MBBA method that uses low-cost reagents and standard cytometers. The key innovation is the use of the essentially irreversible biotin-streptavidin interaction. We prepared a biotin-conjugated fluorescent dye and used it to produce streptavidin-coated magnetic beads that are labeled at distinct levels of fluorescence. We show the utility of our method in characterization of phage-displayed antibodies against multiple antigens of SARS-CoV-2, which substantially improves the throughput and dramatically reduces antigen consumption compared with conventional phage ELISA methods. This approach will make MBBAs more broadly accessible.

Encapsulation of the nematic liquid crystal N-(4-methoxybenzylidene)-4-butylaniline (MBBA) into the core of poly(vinylpyrrolidone) (PVP) microfibers has been accomplished via coaxial electrospinning for the first time. Data from optical microscopy, two-dimensional Raman mapping, differential scanning calorimetry, and dielectric spectroscopy have been employed to gain detailed insights into the confinement effects on MBBA in a semiflexible polymer sheath. The electrospun fiber diameters could be tuned easily by modifying the flow rate of MBBA, and both the MBBA core and PVP sheath diameters were determined via Raman line cuts. The PVP sheath induced alignment of MBBA, where its long axis is parallel to the fiber axis. Further, the alignment of MBBA led to iridescence in the fibers, which was found to be temperature-sensitive and reversible. Surprisingly, at temperatures below 0 °C, the phase-transition temperatures of confined MBBA are different than the neat and one of its smectic phases is inhibited by t...

Photonic crystal fiber (PCF) is employed as a refractive index sensor (RIS) for solving a lot of problems in biological, physicochemical, medical, engineering fields and many environmental challenges, where it is used in many industries of food, medicines, chemical materials and material diagnosis. The kind of the PCFs was HC-1550 with three wavelengths of laser source were used; 638 nm, 850 nm, and 1550 nm that are useful for recording the intended transmitted signal intensity. Therefore, the measured RI was in the range (1.469 - 1.455 RIU) at the temperature range (36 - 70)°C for the EBBA and it was (1.621 - 1.612 RIU) at the temperature range (22 - 42)°C for the MBBA. The results showed that the highest RI sensitivity was 96.335 dBm/RIU for the HC-1550 infiltrated with MBBA using the laser of wavelength 638 nm, Also, the highest temperature sensitivity was 0.2505 dBm/°C for empty HC-1550 using the laser of wavelength 1550 nm.

One-step synthesis of nanocrystals with tunable morphology is an area of both basic and technological interest, the former due to the lack of our understanding regarding the pre-conditions and the mechanism through which entropy is reduced spontaneously and the free energy becomes enthalpy-driven, while the latter stems from the need to grow nanocrystals reproducibly and without external adducts for seeding. Here we will present and discuss results of using the liquid crystalline material MBBA (N-(4-methoxybenzylidene)-4-butylaniline) as a matrix for the synthesis of Au and Ag nanocrystals of tunable morphology. MBBA lacks the smectic phase in its phase diagram and has only the nematic and isotropic phases as equilibrium phases while the other phases are non-equilibrium or glassy phases. We have proved that even the nematic-isotropic phase transition is a non-equilibrium transition that can, however, be turned into an equilibrium transition in presence of enthalpic forces. Using this self-organizing property and the fact that the imine group in MBBA is a reducing agent, we have grown Au and Ag nanocrystals, as also Au-Ag core-shell nanocrystals, of a number of shapes that can be tuned by the temperature and the time of growth. The principle behind the method can be utilized for one-step nanocrystal synthesis in general. In particular, the simultaneous growth of the core and the shell in the highly miscible metals shows that the non-equilibrium conditions set a differential in the growth rates of Au and Ag, causing phase segregation.

In the present work, multiwall carbon nanotube dispersed/doped nematic liquid crystal mixture have been synthesized by ultrasonication technique and studied using dielectric spectroscopy tools in the frequency range of 10 kHz-40 MHz. We have observed that the dielectric permittivity, loss and relaxation frequency of a nematic liquid crystal (MBBA) are influenced by the presence of multiwall carbon nanotube as a function of frequency and temperature. The value of dielectric permittivity increases with the dispersion of multiwall carbon nanotube due to π-π interaction of MWCNT and LC molecules. However, an increase in relaxation frequency is also found in dispersed samples. The MWCNT with almost identical size within themselves are dispersed at 0.5% concentration into nematic LC. The MWCNT-nematic LC composites are not only of fundamental importance, but also useful materials for device applications such as liquid crystal displays.

A new series of chiral dopants, (R)-6,6′-halogenated (1b–1e, X = F, Cl, Br and I) and -methylated (1f) binaphthyl compounds, were designed and synthesized to create chiral liquid crystals by doping them into an achiral nematic liquid crystal (NLC). The influence of halogen (X = F, Cl, Br and I) and methyl substituent factors, such as steric, polar, and polarizability properties, on the helical twisting power (HTP) and their temperature dependences on the chiral dopants were investigated in two host NLCs with different characteristics, fluorinated JC-1041XX and N-(4-methoxybenzylidene)-4-butylaniline (MBBA). The chiral dopants possessing less steric and larger polarizability factors increased the HTP values. The structural similarity and electrostatic arene–arene interactions between the chiral dopants and the NLC molecules also exerted important influences on these values. The temperature dependence of the HTP (HTPt.d.) values also correlated well with the steric and polarizability substituents factors in the two host NLCs. Their correlation coefficients (R2) depended on the molecular structural similarity between the chiral dopant and the NLC.

Influence of fullerenes C60 and single-walled carbon nanotubes (SWCNTs) with concentration of 0.5 wt.% on the Carr-Helfrich electrohydrodynamic instability in nematic liquid crystal 4-methoxybenzylidene-4′-butylaniline (MBBA) is investigated. It is shown that the inclusion of these dopants into liquid crystal leads to decreasing of the threshold voltage of Williams domains formation. Critical frequency of disappearance of the EHDI decreases for the MBBA + fullerenes colloid and it increases for the MBBA + SWCNTs colloid with respect to the pure LC. A decrease of time characteristics in the MBBA + fullerenes colloid and their increase in the MBBA + SWCNTs colloid compared with the pure MBBA are observed. The experimental results are explained on the base of the Carr-Helfrich theory for electrohydrodynamic instability in nematic liquid crystal.

We study the influence of confinement on the rheology and structure of nematic liquid crystals (NLCs). NLCs get confined in networks of titania (TiO2, primary particle size = 21 nm) nanoparticles in suspensions of TiO2 and NLC, N-(4-methoxybenzylidene)-4-butylaniline (MBBA). Suspensions with TiO2 nanoparticle volume fraction (ϕ) of 0.006–0.017, form viscoelastic solids with low elastic modulus (G′) of 101 Pa–102 Pa and short relaxation times. Increase in TiO2 nanoparticle ϕ leads to a rise in G′ with TiO2 nanoparticles forming a percolating network at a critical volume fraction (ϕ c) = 0.023, and G′ of ~103 Pa. TiO2/MBBA NLC suspensions at and above ϕ c = 0.023 show G′ ~ ω x−1 scaling, where ω is the angular frequency and the minimum in loss modulus (G′′) with ω. The effective noise temperature, x decreases and approaches 1 with the increase in the TiO2 nanoparticle ϕ from 0.023–0.035, is indicative of an increase in the glassy dynamics. Through the polarized light microscopy and differential scanning calorimetry experiments, we propose that the progressive addition of TiO2 nanoparticles introduces a quenched random disorder (QRD) in the NLC medium which disturbs the nematic order. This results in metastable TiO2/MBBA NLC suspensions in which NLC domains get confined in the network of flocs of TiO2 nanoparticles. We also show that the salient rheological signatures of soft glassy rheology develop only in the presence of NLC MBBA and are absent in the isotropic phase of MBBA.

Helical twisting powers of a series of ruthenium complexes with screw-like Δ, Λ chirality were investigated in N-(4-Methoxybenzylidene)-4-butylaniline (MBBA). Λ-[Ru(acac)2(trop)] (acac = acetylacetonate, trop = tropolonate) shows a fairly low HTP of 18 µm−1, while we found that the HTP increased almost double by connecting with an achiral bulky unit [Ru(Cp)(dppe)] (Cp = cyclopentadienyl, dppe = 1,2-bis(diphenyl)phosphinoethane) that was found to behave as a molecular “picket fence” to force the orientation of surrounding MBBA molecules.

In this work, MBBA liquid crystal-doped hydrogels are investigated through of Scanning Electron Microscopy (SEM), Polarized Optical Microscopy (POM), Optical Transmittance (OT) and Dielectric Spectroscopy (DS) techniques. For the synthesis of the hydrogels and of their composites a solution (20% water and 80% acetone) of the potassium periodate (KIO 4 ) was prepared. The samples were prepared by radicalar photochemical polymerization of acrylamide monomer (AAm) in the presence of N , N ′-methylene-bis-acrylamide (MBAAm) as a cross-linking agent. Potassium periodate (KIO 4 ) was used as a photopolymerization initiator. In such synthesis, acrylamide monomer (AAm-Aldrich, 14, 866–5) was added with cross-linking agent MBAAm (N, N-methylene-bis-acrylamide) and liquid crystals MBBA (N-(4-methoxybenzilidene)-4(butylaniline)). The acetone was used to solubilize the liquid crystal MBBA in the solution. The resulting solution was placed and sealed between two glass plates coated with transparent and conducting films of tin oxide (SnO 2 ) with spacer of 25 μm. All samples were investigated at 15.0 °C, 23.0 °C and 35.0 °C. The electrical behavior of the samples was characterized by using a Solartron 1260A impedance-gain phase analyzer in the frequency range from 10 mHz to 10 MHz with amplitude of 10 mV. The experimental results from DS technique are discussed by using Davidson–Cole and Havriliak–Negami approaches. As one of main results of this work we noticed that the cavities of the hydrogels synthesized with the use of acetone can be able to confine the free ions of the liquid crystal added to the polymeric matrix.

This article shows the measured dependences of the Frederiksz threshold field for liquid crystal (LCD) MBBA and ferromagnetic suspension (FN) based on it. Magnetite particles (Fe3O4) were used as magnetic particles, the volume fraction of which was f = 4∙10 -4 . Electron microscopy showed that magnetite particles have a quasispherical shape. The particle size distribution is constructed. The average particle diameter was 10 nm. A technique for preparing samples for doping a nematic matrix with ferromagnetic particles and a liquid crystal cell device are described. Dielectric measurements are performed on a precision RLC WK 6505B analyzer in a constant magnetic field with induction from 0 to 0.6 T. It is shown that the Frederiksz threshold field for the FN is significantly smaller than for the nematic matrix. Temperature dependences of the Frederiksz threshold field are constructed. It is shown that with a temperature rise the threshold field values decrease.

This study presents a new method to develop a thin controllable retarder/modulator with spatial axial symmetry by rotating a freely suspended of 4-Cyano-4- n -pentylbiphenyl (5CB) and N -(4-methoxybenzylidene)-4-butylaniline (MBBA) liquid crystal films using mechanical method or as a liquid film motor.

In this work, we explore fluctuations during phase transitions of uniaxial and biaxial liquid crystals using a phenomenological free energy functional. We rely on a continuum-level description of the liquid crystal ordering with a tensorial parameter and a temperature dependent Landau polynomial expansion of the tensor's invariants. The free energy functional, over a three-dimensional periodic domain, is integrated with a Gaussian quadrature and minimized with a theoretically informed Monte Carlo method. We reconstruct analytical phase diagrams, following Landau and Doi's notations, to verify that the free energy relaxation reaches the global minimum. Importantly, our relaxation method is able to follow the thermodynamic behavior provided by other non-phenomenological approaches; we predict the first order character of the isotropic-nematic transition, and we identify the uniaxial-biaxial transition as second order. Finally, we use a finite-size scaling method, using the nematic susceptibility, to calculate the transition temperatures for 4-Cyano-4'-pentylbiphenyl (5CB) and N-(4-methoxybenzylidene)-4-butylaniline (MBBA). Our results show good agreement with experimental values, thereby validating our minimization method. Our approach is an alternative towards the relaxation of temperature dependent continuum-level free energy functionals, in any geometry, and can incorporate complicated elastic and surface energy densities.

This study reported the photoluminescence (PL) of nematic liquid crystal (LC) doped with gold nanoparticles (AuNPs). Our results demonstrated PL emission intensity of MBBA LC is improved with doping AuNPs, and the improvement of PL intensity increased with elevating concentration of AuNPs. As well as, the emission peak is changed due to presence of AuNPs. It was showed PL emission peak of LC has been shifted towards longer wavelength by 78nm in presence of 0.1 AuNPs. A small amount of AuNPs can be improved the PL intensity.

The nonlinear optical (NLO) properties of nematic liquid crystal (LC)N-(4-methoxybenzylidene)-4-n-butylaniline (MBBA)doped with various concentrations of multi walled carbon nanotubes (MWCNTs) have been investigated utilizing Z- scan technique. The obtained results showed that the NLO properties of MBBA LC sample can be varied by changing the concentration of CNTs. A small concentration of carbon nanotubes (CNTs) can be enhanced optical nonlinearity, and the maximum nonlinearity was noticed at the sample doped with 0.1 wt% concentration of CNTs.

This study aimed to evaluate the potential DNA photoprotection of nano-based hydrogels containing a novel benzofuroazepine molecule. Photoprotective property of three benzofuroazepine derivative compounds was assessed by determining a UV light absorptive profile. Nanocapsule suspensions (Eudragit® RS 100 as polymeric wall and medium-chain triglyceride or vitamin E as oil core) containing the benzofuroazepine compound that had the best UV spectral absorption were developed and physicochemically characterized. Photostability assay, bioadhesive property as well as preliminary toxicity parameters (HET-CAM and Artemia salina lethality assays) for free or nanoencapsulated forms were assessed. Among the molecules, the UV absorbance spectrum of free MBBA showed a broad and high intensity absorbance at UVB and UVA ranges. MBBA-nanocapsule suspensions had nanometric and homogeneous size distribution, bioadhesiveness property, and increased the UV light scattering in comparison to the free compound. Besides, all formulations triggered no irritative responses and the nanoencapsulation mitigated the toxic effect to Artemia salina observed to free MBBA. Following, hydrogels were prepared by thickening nanocapsule suspensions with gellan gum and their DNA photoprotection properties were determined by the exposure of DNA samples to the UVB and UVA radiation. Hydrogels showed acid pH values, compound content close to the theoretical value (3 mg/g), particle size in nanometric range, and spreadability profile suitable for cutaneous application. All MBBA hydrogels were effective against photoproducts formation induced by UVB and UVA radiation. In conclusion, these data show the identification of a compound with promising UV absorptive potential and the preparation of a final nano-based hydrogel for cutaneous application.

A novel modified binary bat algorithm (MBBA) with chaos and Doppler effect in echoes is presented in this paper to deal with the fault diagnosis problem of analog circuits with tolerance. The proposed method focuses on further mimicking the bats' behaviors and improving the binary bat algorithm (BBA) in view of biology. The proposed algorithm utilizes the bats' self-adaptive compensation for Doppler effect in echoes and the chaotic optimization method to improve the BBA. The elitist strategy is also used to store all the possible global best solutions, which will provide us with more possible choices in practice. Since single feature extraction method has limitations during fault diagnosis of analog circuits with tolerance, several kinds of feature extraction methods are used together to build a big feature set firstly in our method, and then, the new proposed MBBA is used to select the optimal feature subset simultaneously optimize the classifier parameters for the analog fault diagnosis. Three analog circuits' examples are given to demonstrate the effectiveness and generalization ability of our method, and other methods are also used to do comparisons. The results indicate that combining different kinds of feature extraction method together to optimally select the feature subset simultaneously optimize the classifier parameters by MBBA can obtain better performance in dealing with analog fault diagnosis problems, and our proposed method provides a better tradeoff between fault diagnosis accuracy and total cost, which is superior to other methods. Therefore, it is an effective method for analog fault diagnosis and has broad application prospects in practice.

Dielectric dispersions in the homogeneous () and the homeotropic () aligned cells in the nematic phase of PCPB/MBBA mixtures have been measured in the frequency range between 100 Hz and 1 MHz. The Cole–Cole formula accounting for DC conduction has been found to reproduce dielectric dispersions well in all of the mixtures. The crossover frequency monotonously increases with increasing the MBBA concentration. It has been also found that the strengths of dielectric anisotropy both in the high and the low frequency regions are enhanced by adding of MBBA at least below 50 mol%. The dielectric anisotropy in the present system has been discussed qualitatively on the basis of the Landau-type free energy density.

We present a 17O and 1H NMR study of molecular endofullerene H2O@C60 dissolved in the nematic liquid crystal N-(4-methoxybenzylidene)-4-butylaniline (MBBA). The 17O NMR peak is split into five components by the 17O residual quadrupolar coupling, each of which is split into a triplet by the 1H–17O residual dipolar coupling and scalar coupling. The splittings are analysed in terms of the partial alignment of the encapsulated water molecules. Order parameters describing the alignment are estimated. It is found that the preferential orientation of the endohedral water molecule has the molecular plane perpendicular to the liquid crystal director.

Photo-responsive double emulsions made of liquid crystal (LC) were prepared by a microfluidic device, and the light-induced processes were studied. The phase transition was induced from the center of the topological defect for an emulsion made of (N-(4-methoxybenzylidene)-4-butylaniline (MBBA), and strange texture change was observed for an emulsion made of 4-cyano-4′-pentylbiphenyl (5CB) doped with azobenzene. The results suggest that there are defect-involved processes in the phase change of LC double emulsions.

In this work, we have analyzed the experimental pressure-temperature behavior at the isotropic-nematic phase transition of the liquid crystals PAP, 5CB, MBBA, and EBBA at 1 atm by using the HERSW Convex Peg model in conjunction with the IPCM model. We have calculated the molecular volume values for the hard and attractive cores from theoretical quantum calculations at the PM3, PM6, B3LYP/6-311++G(d,p)//PM6, and M06/6-311++G(d,p)//PM6 levels of theory. The results suggest that the best theoretical prediction of the experimental pressure-temperature behavior is obtained when the molecular volume is evaluated at the DFT level.

Microwave heating effects are widely used in the acceleration of organic, polymerization and enzymatic reactions. These effects are primarily caused by the local heating induced by microwave irradiation. However, the detailed molecular mechanisms associated with microwave heating effects on the chemical reactions are not yet well understood. This study investigated the microwave heating effect of N-(4-methoxybenzylidene)-4-butylaniline (MBBA) in liquid crystalline and isotropic phases using in situ microwave irradiation nuclear magnetic resonance (NMR) spectroscopy, by obtaining (1)H NMR spectra of MBBA under microwave irradiation. When heated simply using the temperature control unit of the NMR instrument, the liquid crystalline MBBA was converted to the isotropic phase exactly at its phase transition temperature (Tc) of 41 °C. The application of microwave irradiation at 130 W for 90 s while maintaining the instrument temperature at 20 °C generated a small amount of isotropic phase within the bulk liquid crystal. The sample temperature of the liquid crystalline state obtained during microwave irradiation was estimated to be 35 °C by assessing the linewidths of the (1)H NMR spectrum. This partial transition to the isotropic phase can be attributed to a non-equilibrium local heating state induced by the microwave irradiation. The application of microwave at 195 W for 5 min to isotropic MBBA while maintaining an instrument temperature of 50 °C raised the sample temperature to 160 °C. In this study, the MBBA temperature during microwave irradiation was estimated by measuring the temperature dependent chemical shifts of individual protons in the sample, and the different protons were found to indicate significantly different temperatures in the molecule. These results suggest that microwave heating polarizes bonds in polar functional groups, and this effect may partly explain the attendant acceleration of organic reactions.

We report the NMR of the molecular endofullerenes H2@C60, H2O@C60 and HF@C60 dissolved in the nematic liquid crystal N-(4-methoxybenzylidene)-4-butylaniline (MBBA). The 1H NMR lines of H2 and H2O display a doublet splitting due to residual dipole–dipole coupling. The dipolar splitting depends on temperature in the nematic phase and vanishes above the nematic–isotropic phase transition. The 19F spectrum of HF@C60 dissolved in MBBA displays a doublet splitting in the nematic phase, with contributions from the 1H–19F dipole–dipole coupling and J-coupling. The phenomena are analyzed using a model in which the fullerene cages acquire a geometrical distortion, either through interaction with the liquid crystal environment, or through their interaction with the endohedral molecules. The distorted cages become partially oriented with respect to the liquid crystal director, and the endohedral molecules become partially oriented with respect to the distorted cages.

The prediction of a theory developed with allowance for the processes of orientational order parameter relaxation in liquid crystals about two independent acoustic mechanisms of orientational instability in the planar layer of a cholesteric liquid crystal (CLC) in a wave field, manifesting itself in the occurrence of a system of 2D domains, is experimentally substantiated for the first time. The distortions of the layer macrostructure for the mesophase of this type was observed in the field of longitudinal waves in a wide frequency range, including frequencies above the relaxation frequency of the orientational order parameter in CLC. The values of the spatial domain period at the effect threshold and the threshold compression amplitudes are determined for CLC layers 10–100 μm thick with a helix pitch of 2–30 μm in the frequency range of 0.3–45 MHz. It is shown that a complete theoretical description of the phenomenon, consistent with the experimental data, can be obtained only with allowance for the action of the convection and the nonlinear relaxation mechanisms of the mesophase layer structure destabilization, which have different natures.

The influence of the orientational order of molecules in a nematic liquid crystal on the mean value and anisotropy Δγ of the molecular polarizability has been studied in the framework of the molecular sta� tistical approach with allowance for the perturbation of the electronic structure of molecules due to the change in the conformation of their aromatic core and intermolecular interactions. Experimental depen� dences of and Δγ on the molecular orientational order parameter S have been derived, and their specific features for the known objects have been explained. The possibility of separating the contributions of opposite signs to the dependence Δγ(S) due to the change in the conformation of molecules and intermolecular inter� actions has been shown using nematic MBBA as an example.

Keywords: nematic liquid crystal, grid pattern, image proces sing, dimensional analysis. Grid pattern (GP) is observed on planarly aligned nematic liquid crystal 4-methoxy-benziledene-4-n-buthyl-aniline (MBBA) when it is applied by a certain frequency and a certain voltage that exceeds a threshold voltage, VGP. The GP appears due to convective movements of MBBA molecules. Dimensions on GP are distinguished into the length and width of GP rectangular shape. Width-area of GP is a product of the length and the width. Dimensional analysis is carried on image processing using ImageJ software. Observation on the pattern shows that the frequency affects GP dimensions, which are proportional to the GP length and inversely proportional to the GP width. Variation on frequency also shows that the frequency is inversely proportional to GP width-area. Dimensional analysis also describes a quadratic relation between frequency and width-area of GP.

This study discusses the fabrication and characterization of optically responsive microfibers with uniaxially ordered nematic liquid crystal molecules at their core. The liquid crystal microfibers were electrospun from a solution of polyvinylpyrrolidone (PVP) and N-(4-methoxybenzylidene)-4-butylaniline (MBBA). A study of phase transition and optical behavior was performed using optical observation by polarized optical microscope, and intermolecular interaction was investigated using Fourier transform infrared (FTIR). The diameter, orientational order of the fibers and light intensity that passed through the fibers depended on the MBBA concentration during the electrospinning process. The nematic–isotropic temperature (T NI) of PVP–MBBA microfibers shifted lower from the T NI of MBBA. Meanwhile a reverse correlation between MBBA concentrations and phase transition was found in the isotropic phase; a significant increase in temperature rate and response time was occurred with small weightage of MBBA. FTIR measurement confirmed that the liquid crystal molecules were self-phase separated from the PVP chains in the fibers.

The Lorentz tensor components Lj and the polarizability tensor components γj of 4-methoxyben-zylidene-4′-butylaniline (MBBA) liquid crystal molecules in nematic and isotropic phases have been determined experimentally. The quadratic dependences of the mean value \(\bar \gamma \) (S) and anisotropy Δγ(S) of the polarizability in the nematic phase on the orientational order parameter S of molecules have been established. Within the phenomenological approach, the dependences \(\bar \gamma \) (S) and Δγ(S) have been derived, and their features for MBBA and other known objects have been interpreted. The relation of the dependences \(\bar \gamma \) (S) and Δγ(S) to the features of the nematic-isotropic liquid phase transition has been found.

Molecular dynamics of 4-methoxybenzylidene-4- n -butylaniline (MBBA) in a liquid crystal cell after the perturbation of a UV pulse was observed using the polarization dependent heterodyne transient grating (HD-TG) method. The response of a refractive index change showed different signs depending on the probe polarization, and each response was composed of 4 exponential components. These components were assigned to disordering, 2 types of ordering, and molecular diffusion, judged from the sign of the refractive index change and the dependence on the grating spacing and the pump intensity. The time constants for the disordering and the ordering processes drastically increased for the pump intensity above 0.10 mJ/pulse. To explain the threshold, we proposed that disordering/ordering of domains were observed for the higher pump intensities, while an individual molecule is subject to disordering/ordering for the lower pump intensity.

In this work, the nematic liquid crystal (LC) N-(4′-methoxybenzylidene)-4-n-butylaniline (MBBA) was prepared and doped with different concentrations (0.025, 0.05, 0.06, 0.07, 0.08, and 0.1 wt.%) of multi-walled carbon nanotubes (CNTs) at room temperature to study the electric properties of (LC–CNTs) cell. The experimental results showed that capacitance of (LC–CNTs) cell became higher than that of pure LC cell. The dielectric permittivity is determined as a function of applied frequency (100 Hz to 100 kHz) at voltage (5 V); it is found that increasing concentration of CNTs (0.1 wt.%) led to increase in the real part dielectric constant and decrease in imaginary part for (LC–CNTs) cell compared with the pure liquid crystal. Also conductivity of (LC–CNTs) cell was increased with increasing concentration of CNTs more than 0.05 wt.%. Theoretical study was carried out by using PM3 method for stable geometries of a nematic liquid crystal molecule of MBBA assembled parallel on a molecule of single-walled carbon nanotube (CNT). The result showed that the interaction caused by π,π-stacking between MBBA molecule and the wall of CNT and that may lead to formation of the local short range orientation order by LC molecules on the surface of the CNT. The binding energy of the LC molecule on the CNT wall was within the typical van der Waals interaction.