LC Phase Research Articles

Dynamic Switching of the Circularly Polarized Luminescence of Disubstituted Polyacetylene by Selective Transmission through a Thermotropic Chiral Nematic Liquid Crystal

AbstractThe circularly polarized luminescence (CPL) of chiral disubstituted liquid‐crystalline polyacetylene (di‐LCPA) can be dynamically switched and amplified from left‐ to right‐handed CPL and vice versa through the selective transmission of CPL across a thermotropic chiral nematic liquid crystal (N*‐LC) phase. By combining a chiral di‐LCPA CPL‐emitting film with an N*‐LC cell and tuning the selective reflection band of the N*‐LC phase to coincide with the CPL emission band, a CPL‐switchable cell was constructed. The phase change induced by the thermotropic N*‐LC cell by varying the temperature leads to a change in the selective transmission of CPL, which enables the dynamic switching and amplification of CPL. It is anticipated that CPL‐switchable devices might find applications in switchable low‐threshold lasers and optical memory devices.

Dynamic switching of the circularly polarized luminescence of disubstituted polyacetylene by selective transmission through a thermotropic chiral nematic liquid crystal.

The circularly polarized luminescence (CPL) of chiral disubstituted liquid-crystalline polyacetylene (di-LCPA) can be dynamically switched and amplified from left- to right-handed CPL and vice versa through the selective transmission of CPL across a thermotropic chiral nematic liquid crystal (N*-LC) phase. By combining a chiral di-LCPA CPL-emitting film with an N*-LC cell and tuning the selective reflection band of the N*-LC phase to coincide with the CPL emission band, a CPL-switchable cell was constructed. The phase change induced by the thermotropic N*-LC cell by varying the temperature leads to a change in the selective transmission of CPL, which enables the dynamic switching and amplification of CPL. It is anticipated that CPL-switchable devices might find applications in switchable low-threshold lasers and optical memory devices.

Mesomorphism of a new series of catanionic 4-(1-pentylheptyl)benzenesulfonates.

The effect of cationic chemical structure on the mesophase behavior, and self-assembly of catanionic compounds is studied through a systematic structure variation of six cationic surfactants with anionic sodium 4-(1-pentylheptyl)benzenesulfonate surfactant. A series of cationic surfactants are selected with an increasing number of n-dodecyl chains on the same ammonium headgroup (from one to three), and with an increasing number of ammonium headgroups (from two to four). Thermal and phase behavior of the synthesized products were examined by thermogravimetry, polarizing microscopy, differential scanning calorimetry, powder and grazing incidence X-ray diffraction, and molecular simulation. The compounds are complexes of high thermal stability. Most of the thermotropic mesophases are smectic, although the hexagonal mesophase is also observed. Introduction of the third dodecyl chain into the cationic part leads to pronounced lower melting temperatures and eradicates mesomorphism, while the addition of a fourth ammonium headgroup leads to a catanionic benzenesulfonate that decomposes simultaneously under melting. Melting and crystallization temperatures show nonlinear dependence on the total number of alkyl chains, and on the number of headgroups in the molecule. Molecular dynamics simulation of the smectic phase points to separated hydrophilic and hydrophobic layers, favoring head-to-head packing of antiparallel molecules. On the other hand, there are two ion pairs in the column cross-section of the hexagonal LC phase of didodecyldimethylammonium-4-(1-pentylheptyl)benzenesulfonate.

Hepatitis B surface antigen levels during natural history of chronic hepatitis B: a Chinese perspective study.

To determine the baseline hepatitis B surface antigen (HBsAg) levels during the different phases of chronic hepatitis B (CHB) patients in China. Six hundred and twenty-three hepatitis B virus or un-infected patients not receiving antiviral therapy were analyzed in a cross-sectional study. The CHB patients were classified into five phases: immune-tolerant (IT, n = 108), immune-clearance (IC, n = 161), hepatitis B e antigen negative hepatitis (ENH, n = 149), low-replicative (LR, n = 135), and liver cirrhosis (LC, n = 70). HBsAg was quantified (Abbott ARCHITECT assay) and correlated with hepatitis B virus (HBV) DNA, and serum alanine aminotransferase/aspartate aminotransferase (ALT/AST) in each phase of CHB was also determined. Median HBsAg titers were different in each phase of CHB (P < 0.001): IT (4.85 log10 IU/mL), IC (4.36 log10 IU/mL), ENH (2.95 log10 IU/mL), LR (3.18 log10 IU/mL) and LC (2.69 log10 IU/mL). HBsAg titers were highest in the IT phase and lowest in the LC phase. Serum HBsAg titers showed a strong correlation with HBV viral load in the IC phase (r = 0.683, P < 0.001). No correlation between serum HBsAg level and ALT/AST was observed. The mean baseline HBsAg levels differ significantly during the five phases of CHB, providing evidence on the natural history of HBV infection. HBsAg quantification may predict the effects of immune-modulator or oral nucleos(t)ide analogue therapy.

Separation of enantiomers on chiral stationary phase based on chicken α1-acid glycoprotein: Effect of silica particle diameters on column performance

The effects of silica particle diameters on performances of chicken α1-acid glycoprotein (c-AGP)-immobilized silica particle columns were investigated. c-AGP was immobilized onto aminopropyl silica particles, whose nominal particle diameters were 5, 3 and 2.1μm, activated with N,N′-disuccinimidyl carbonate. The retention factor (k), enantioseparation factor (α), resolution (Rs) and height equivalent to a theoretical plate (H) of solutes on three c-AGP columns were evaluated using a mixture of phosphate buffer and organic modifier as a mobile phase in LC. There were not so much differences in their k and α values among three c-AGP columns, while their Rs values were in the order of 2.1μm>3μm>5μm silica particles and their H values were in the reversed order. Since three c-AGP columns gave almost the same enantioseparation factors for solutes, their highest Rs and lowest H values on a c-AGP-immobilized column prepared with 2.1-μm silica particles came from its highest column efficiency among there c-AGP columns. These results suggest that 2.1-μm silica particles could be useful for the preparation of c-AGP- or protein-based CSPs.

Modulated SmA(b) phases formed by anchor shaped liquid crystalline molecules.

Bent-core molecules with a linear alkyl chain in the bay position (anchor shaped molecules) form new liquid crystalline phases combining periodicities with different coherence lengths in distinct directions; in these LC phases the molecules are organized on average orthogonal in modulated layers (ribbons or patches) with restricted rotation around the long axis, thus representing modulated SmA(b) phases.

Detecting complex eruption sequence and directionality from high-rate geodetic observations: The August 6, 2012 Te Maari eruption, Tongariro, New Zealand

The Tongariro Te Maari crater, New Zealand, erupted for the first time in over 80years on August 6, 2012. Because it occurred at night, the short-lived eruption prevented direct visual observations, hence presenting some challenges for understanding the complex eruptive sequence and reach of the various explosions. Using 1Hz Global Positioning System (GPS) data from the local volcano monitoring network, we computed the GPS LC phase residuals and SNR data at the time of the eruption and show that several processes successively affected the signal at the closest GPS station. Firstly, the signal from one of the satellites shows two successive drops of SNR caused by the presence of two distinct dense ash-laden plumes near the vent, produced successively by the second and last of the main eruption pulses. Secondly, we show that a gas-charged debris avalanche and a lateral blast successively entrained hot and/or humid air over 3km away from the vent, atop the VGKR GPS station. While the limited amount of data prevents fully quantitative analyses and estimates of temperature or humidity in the lateral air flow, our results document the first recorded detection of a small-scale lateral plume by GPS technology. They highlight the potential of GPS data analysis for improving our understanding of eruptive sequences when visual observations are limited.

Ferroelectric phases in non-symmetric achiral bent liquid crystals towards ambient temperatures: a novel series with oxadiazol as central moiety

Extensive survey carried out in bent liquid crystals (BLCs) exhibiting ferroelectric (FE) phases suggested for the design of non-symmetric (NS) frame. Novel series of BLCs (C8Cm) with distinct lateral moieties and heterocyclic central (oxadiazole) moiety, viz., octyl 4-(5-(4´-(alkyloxy) biphenyl-4-yl)-1,2,4-oxadiazol-3-yl)benzoates, are reported. NS BLC frame is realised by incorporating differing number of aromatic cores and varied length of end chains in the lateral moieties. Lateral moiety with biphenyl core is prepared by Suzuki coupling. Purity of the BLC product is confirmed by 1H NMR and elemental analysis. LC phases exhibited by C8Cm series of BLCs for m = 8, 10, 12, 15 and 16 are characterised by polarisation optical microscopy (POM), differential scanning calorimetry (DSC) and spontaneous polarisation (PS) techniques. C8Cm series are found to exhibit SmA, CrystalB, B2, B5, SmG and SmE phase variance. SmG occurs as monotropic phase. Temperature variation of PS(T) studied in FE B2 and B5 phases by field reversal method infers a moderate PS value of ~80–100 nC · cm−2. Order parameter growth in FE B2 and B5 phases is analysed through PS(T). Normalised order parameter θN exhibits asymptotic behaviour with universal temperature TU. Influence of aromatic cores and length of end chains (in lateral moieties) on the thermal stability of FE phases is discussed in the wake of the data on other BLCs.

The influence of intraannular templates on the liquid crystallinity of shape-persistent macrocycles.

A series of shape-persistent phenylene–ethynylene–naphthylene–butadiynylene macrocycles with different extraannular alkyl groups and intraannular bridges is synthesized by oxidative Glaser-coupling of the appropriate precursors. The intraannular bridges serve in this case as templates that reduce the oligomerization even when the reaction is not performed under pseudo high-dilution conditions. The extraannular as well as the intraannular substituents have a strong influence on the thermal behavior of the compounds. With branched alkyl chains at the periphery, the macrocycles exhibit liquid crystalline (lc) phases when the interior is empty or when the length of the alkyl bridge is just right to cross the ring. With a longer alkyl or an oligoethylene oxide bridge no lc phase is observed, most probably because the mesogene is no longer planar.

A Small Change in Central Linker Has a Profound Effect in Inducing Columnar Phases of Triazine‐Based Unconventional Dendrimers

Four unconventional triazine-based dendrimers have been prepared and characterized by (1) H and (13) C NMR spectroscopies, mass spectrometry, and elemental analysis. Based on DSC studies, polarizing microscopy, and powder XRD, two of these dendrimers, containing linkers with an odd number of carbon atoms, were observed to display columnar liquid-crystalline phases during thermal treatment. However, the other two dendritic analogues, containing linkers with an even number of carbon atoms, were not observed to behave correspondingly. Based on computer simulation, we reasonably assume that the dendrimers with an odd number of carbon atoms in their linkers distort their molecular shape and adopt two isomeric structures due to asymmetrical congestion. This reduces the molecular π-π face-to-face interaction, which in turn causes the dendrimers to form columnar LC phases during thermal treatment. However, the dendrimers with an even number of carbon atoms in their linkers have more symmetrical skeletons and do not display any liquid-crystalline phase upon thermal treatment. This new strategy should be applicable for eliciting the columnar liquid-crystalline properties of other types of unconventional dendrimers with rigid frameworks.

Photoresponsive Smectic Liquid Crystalline Multipods and Hyperbranched Azo Polymers

Liquid crystalline azobenzene containing triped and tetraped monomers were designed and synthesized and further used as B3 and B4 type monomers to form hyperbranched polymers with tetraethylene glycol as the A2 type comonomer. The mesophase characteristics of the multiarm-star mesogens and hyperbranched polymers were analyzed using various instrumentation techniques like differential scanning calorimetry (DSC), polarized light microscopy (PLM) and variable temperature XRD. The multipod monomers as well as hyperbranched polymers exhibited thermotropic smectic liquid crystalline characteristics with a tendency toward higher ordered smectic LC phases with increased branching. The hyperbranched polymers exhibited lamellar organization even in the as-solvent precipitated powder sample indicating higher extent of nanosegregation. Their potential application as fast switching photochromic materials was highlighted by carrying out isothermal photoswitching experiments in the LC state. Reversible isothermal smectic-isotropic phase transition could be achieved by UV irradiation in <1 s in the multipod monomers, while it required >2 s UV irradiation in the case of the hyperbranched polymers.

Miniaturized overlapped LC phase delay line

A novel miniaturized ultra-wide bandwidth (DC–35 GHz) LC phase delay line (PDL) based on overlapped meander inductors and air-bridge capacitors is proposed and fabricated. Two 45º and 90º PDLs were designed using a semi-lumped model, and the parameters were calculated and optimized based on transmission line theory and 3D simulations. The lengths of the 45º and 90º delay lines are 110 μm and 286 μm, respectively, which represent respective length reductions of 50% and 75% when compared with the corresponding conventional transmission lines. Over the entire operating band, the phase error is less than 0.6º for the 45º PDL and 2.5º for the 90º PDL. The return loss (S11) for both PDLs is better than 15.5 dB, while the insertion loss (S21) is less than 0.62 dB for both devices. Measured results show perfect consistency with the simulation results for these PDLs, and demonstrate the validity of the corresponding model.

The effects of Saccharomyces cerevisiae strains on the rumen fermentation in sheep fed with diets of different forage to concentrate ratios

The objective of this study was to compare the effects of two different Saccharomyces cerevisiae yeast strains on the rumen fermentation of sheep fed with two different total mixed rations. Three rumen-cannulated Merino wethers were used in a pilot study in which a phase of feeding a higher proportion of concentrate in the diet (HC; forage to concentrate ratio 40:60, as fed) was followed by a phase of lower proportion of concentrate in the diet (LC; forage to concentrate ratio 49:51, as fed). Both phases consisted of three 3-week periods as follows: no yeast supplementation, trehalose non-producing and trehalose-producing S. cerevisiae supplementations, respectively. Rumen fluid samples taken in the last days of each period were measured for pH, short chain fatty acid (SCFA) concentrations and ammonia content. The degradability of neutral detergent fibre (NDF) and starch was estimated by the in sacco method. Supplementation with the trehalose non-producing strain did not alter any variables tested in the HC phase. In the LC phase, though degradability was not altered, total SCFA concentration increased, resulting in a decrease of rumen fluid pH. The trehalose-producing strain increased total SCFA content and effectively prevented the consequent decrease in pH in both phases. These effects were more pronounced in the high-concentrate phase, as shown by higher molar proportion of propionate, increased level of ammonia content, and higher ruminal degradability of NDF and starch compared to control and the trehalose non-producing yeast strain.

Supramolecular transformation from ordered columnar to disordered columnar to tetragonal micellar structures in clicked dodeca-alkylated discotic triphenylene liquid crystals

We prepared three discotic liquid crystals (DLCs) based on a triphenylene (TP) disc functionalized with twelve alkyl peripheries. The synthesis of the discogens was performed by a click reaction using Cu(OAc)2 as the catalyst, with six triazolyl groups connecting the TP core with twelve alkyl chains. According to thermal data from differential scanning calorimetry (DSC), discogen , which has the shortest hexyl peripheries, exhibited two LC phases, and and , with decyl and tetradecyl peripheries, respectively, displayed three LC phases as a function of the temperature. Structural analyses using small- and wide-angle X-ray scattering (SAXS and WAXS) techniques revealed ordered and disordered hexagonal columnar LC phases in all the discogens. On the other hand, an unconventional micellar phase with P42/mnm symmetry consisting of thirty micelles was found only in and , when the temperature increased. The thermally induced transformation from the columnar to the micellar phase can be explained by increased chain entropy at higher temperatures. The complex micellar packing in the noncubic phase is attributed to the softness of the DLC micelles because the micellar corona consists of flexible alkyl chains. The discogen design concept in this study (i.e., the introduction of multibranched alkyl peripheries to the discotic mesogens via click chemistry) resulted in unconventional columnar-to-micellar transformation in conventional TP DLCs.

A self-correcting quadrature voltage controlled oscillator

A self-correcting quadrature voltage controlled oscillator (QVCO) with phase correcting loop is proposed. It comprises the QVCO core and phase correcting loop, which corrects the quadrature phase error. Two LC VCOs, buffers, and phase shifters are coupled in circular configuration to achieve IQ symmetry. This paper introduces the idea of realizing QVCO with low phase noise and accurate quadrature phase by using the phase correcting loop. The simulation results based on the 65 nm CMOS process show that the self-correcting QVCO has a phase error less than 0.5° and 1 MHz offset phase noise of −120 dBc/Hz at 3.7 GHz with 49% tuning range.

Synthesis and mesomorphic properties of laterally fluorinated alkyl 4′′-alkylterphenyl-4-yl carbonate liquid crystals

Fifteen series of homologues of a variety of mono-, di- and trifluorosubstituted alkyl 4′′-alkylterphenyl-4-yl carbonates have been synthesized and their mesomorphic properties have been determined. From among 95 prepared compounds, 40 pure nematogens have been found, as well as 55 mesogens with orthogonal and tilted smectic phases in broad temperature ranges. The type and combination of the LC phase strongly depend on the position and number of the fluorine atoms. Physical properties and correlations between the molecular core fluorosubstitution, the length of the terminal chains and the type and sequence of the liquid crystalline phases, have been determined. The compounds are useful for the formulation of nematic mixtures as well as ferroelectric ones.

4-Methylresorcinol based bent-core liquid crystals with azobenzene wings – a new class of compounds with dark conglomerate phases

Stochastic achiral symmetry breaking in soft matter systems, leading to conglomerates of macroscopically chiral domains (so-called dark conglomerate = DC phases) is of contemporary interest from a fundamental scientific point of view as well as for numerous potential applications in chirality sensing and non-centrosymmetric materials. Herein we report the synthesis and investigation of first azobenzene containing bent-core mesogens derived from 4-methylresorcinol forming DC phases with a new structure, distinct from the known fluid sponge-like distorted smectic phases as well as from the helical nano-filament phases (HNF phases, B4 phases). The effects of chain length and other structural modifications on achiral symmetry breaking were investigated. Homologues with relatively short alkyl chains form achiral intercalated lamellar LC phases (B6 phases), but on increasing the chains, these are replaced by the chiral and optically isotropic DC phases. Compounds with the longest alkyl chains form low birefringent crystalline conglomerates which represent less distorted versions of the optically isotropic DC-phases. Introducing additional peripheral substituents at both outer rings removes the DC phases. The DC phases were also removed and replaced by modulated smectic phases if the azo groups were replaced by ester units, showing that azo groups favour DC phase formation with new nanostructures, distinct from the previously known types.

Stimuli responsive chiral liquid crystal phases of phenylboronic acid functionalized rodlike viruses and their interaction with biologically important diols.

The rodlike M13 viruses with chemically decorated phenylboronic acid moieties form pH responsive chiral nematic liquid crystal (LC) phases. Binding with biologically important diols results in LC phases with microstructures that closely correlate with the molecular structure of the diols and can be conveniently discerned by visual cues.

Helical polydiacetylene prepared in the liquid crystal phase using circular polarized ultraviolet light

Herein the enantio-selective polymerization of diacetylene (DA) units in the discotic hydrogen-bonding complex is carried out in an asymmetric reaction field consisting of the lamellar columnar LC phase and CPUL stimulus.

LC phase bias investigation of ASG-EUPOS stations

Abstract Monitoring of permanent stations that make up the reference frame is an integral part of the geodesists work. Selection of reference stations is based on analysis of parameters characterizing them (hardware, coordinates’ stability, mounting, location). In this paper, we took into account phase residual as an indicator of unmodelled signal. Phase residuals were computed based on ASG-EUPOS and EPN observation processing. The results show the connection between the method of mounting the antenna and the residuals. We have reviewed multipath effect at ASG-EUPOS stations, and chosen those which are characterized by the highest value of phase residual. The results show that LC phase residual is a good factor to characterize site’s solutions’ reliability. For majority of sites RMS values were less than 10 mm. Modulations associated with multipath effect were observed for few ASG-EUPOS sites only. Phase residuals are distributed specifically for sites, which antennas are mounted on pillars (more common for EPN sites). For majority of analysed sites phase residual distribution was similar for different days and did not depend directly on atmosphere condition.