Pseudo-rodlike molecules with hockey-stick-shaped mesogen

Hockey-stick-shaped molecules were newly synthesised to obtain pseudo-rodlike molecules. The designed molecules consist of a polar terminal ring (i.e. 2,3,4-, 2,4,6- or 3,4,5-trifluorophenyl group), a rigid middle block (i.e. four rings with aligned ester linkages) and a flexible terminal chain (i.e. dodecyloxy group). We found that the compounds with 2,3,4- and 3,4,5-trifluorophenyl groups formed a smectic A mesophase with head-to-head bi-layer building blocks, whereas the compound with 2,4,6-trifluorophenyl group formed a nematic mesophase. This might be concerned with the behaviour of pseudo-rodlike molecules     

双酚-F不饱和液晶化合物的合成与表征

以4,4'-二羟基二苯基甲烷(双酚-F),3-溴1-丙烯(或6-溴1-己烯)为原料合成了p-BAMBP,p-MBPAB和p-MBPHB三种新型含有不同长度不饱和末端基的液晶化合物,并用POM﹑FTIR、1H-NMR、DSC和XRD进行了表征.结果表明它们均为近晶型液晶,且熔点随柔性末端基增长而降低,相转变温度范围变宽.此类化合物有望作为新型液晶化合物或设计新型液晶功能高分子材料使用.     

A new fluorescence chemosensor based on benzothiazole derivative for Zn2+ and its logic gate behavior

A novel benzothiazole derivative J as a fluorescent chemosensor for Zn²⁺ has been designed and synthesized. The chemosensor J exhibits high selectivity and sensitivity to Zn²⁺ as fluorescence “turn-on” behavior, which the other cations do not make sense. The detection limit calculated by fluorescence titration method was 1.64 × 10^?8 M. Furthermore, the generated J-Zn²⁺ ensemble could recover the enhanced fluorescence upon the addition of EDTA generating an “on-off-on” recycle. In addition, the test strip based on J was fabricated, which could act as a convenient and efficient Zn²⁺ test kit.     

Solid phase synthesis of benzothiazole and thiophene derivatives based on resin-bound cyclic malonic acid ester

A new method for the solid phase synthesis of benzothiazoles and 2-arylamino-3-carboxyl-4-hydroxy-5-arylthiophenes is described. Resin bound cyclic malonic acid ester was reacted with aryl isothiocyanates and then with bromine or α-bromoketones, followed by treatment with perchloric acid or sodium methoxide to afford substituted 2-methylbenzothiazoles or 2-arylamino-3-carboxyl-4-hydroxy-5-arylthiophenes, respectively, in high yields and purities.     

Crystal Structure of 3- (4-Methoxyphenyl )- 1-methylpyrrolo [2, 1-b] benzothiazole

lINTR0DUCTI0NSincebiologicalandpharmacol0gicalactivitieshavebeenwellknownfornumer-ousheterocyc1icar0matictricyc1es""',muchattenti0nhasbeenpaidtothesynthesisoftheheterocycliccompoundswithnovelringsystem(').Inrecentyears,ourwork-inggr0uphassynthesizedaseries0f1,5-benzothiazepineandl,5-benz0diazepinetri-cyclicderivativesandstudiedtheirstructurest4~10i.l,3-Disubstituded-pyrr0l0F2,1-bjbenz0thiazo1eshavebeenobtainedasmainbyproductsinthecycloadditionreactionofl,5-benzothiazepineswithdichl0rocarbe…     

Corrosion inhibitor by a polymerizable columnar mesogen based on hexabenzocoronene derivative

A hexa-peri-hexabenzocoronene derivative (HBC-1,2,4-Ph-DA-C₁₂) with the central HBC core tethered with three diacetylene (DA)-containing chains and three saturated alkyl chains was applied for the anticorrosion of an iron surface. This compound, which exhibits a columnar liquid crystalline phase, could be polymerized by ultraviolet irradiation through reactions between the DA units. This polymer coating exhibited a good anticorrosion property with good hydrophobicity (contact angle [CA] ~ 84°–105°) and excellent mechanical property. It showed a high resistance of 149 kΩ/cm², much higher than that of known anticorrosion materials.     

Nitro substitution in achiral calamitic liquid crystals

This review examines in some detail the effect of terminal and lateral nitro substitutions in achiral calamitic liquid crystals on their physico-chemical properties. The results of this study are compared with those obtained for other groups, and are rationalized in terms of existing theories.     

Fluorescence study on a liquid‐crystalline polyester containing naphthoate mesogen units

Using fluorescence spectroscopy, we investigated intermolecular interaction between mesogenic units in a thermotropic main‐chain LC polyester, P(HBA73/HNA27), containing oxybenzoate (HBA) and oxynaphthoate (HNA) mesogenic units. It is known that P(HBA73/HNA27), which has a high molecular weight, shows second harmonic generation (SHG) activity. P(HBA73/HNA27) showed fluorescence at 410 nm and 430 nm, originating from two kinds of intermolecular interaction. Fluorescence with a peak at 410 nm comes from the ground‐state complex between partially overlapping naphthoate units or between naphthoate and oxybenzoate units whose interaction is weak. Fluorescence at 430 nm comes from the ground‐state complex between fully overlapping naphthoate units whose interaction is strong. The relative fluorescence intensity for 430 nm compared to 410 nm increases with increases in inherent viscosity, η_inh, of P(HBA73/HNA27), the composition ratio of HNA/HBA, and temperature. The fluorescence intensity ratio, I₄₃₀/I₄₁₀, of P(HBA73/HNA27) shows the same inherent‐viscosity dependence with its sudden increase at η_inh = 1.4 ∽ 2.2 dL/g as its SHG activity does, supporting the polar structure and uniformity of LC orientation of the present LC polyester. © 2000 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 38: 2922–2928, 2000     

Synthesis and characterization of N‐substituted polyaniline with mesogen molecules

The N‐substituted polyaniline (PANi) was synthesized by incorporation of bromine‐terminated mesogens onto the emeraldine form of polyaniline. Firsty three liquid crystalline molecules containing biphenyl units were synthesized. These mesogenic molecules are named as: 6‐bromo‐ (4‐hexyloxy‐biphenyl‐4′‐oxy) hexane (C₆? C₆Br), 5‐bromo‐(4‐hexyloxy‐biphenyl‐4′‐oxy) pentane (C₆? C₅Br), 6‐bromo‐(4‐octyloxy‐biphenyl‐4′‐oxy) hexane (C₈? C₆Br). Differential scanning calorimetry (DSC) in combination with polarizing optical microscopy (POM) were used to investigate the thermal properties of them. Optical microscopy showed focal conic texture characteristic of the Smectic A phase for (C₆? C₅Br) and (C₈? C₆Br). For (C₆? C₆? Br) smectic phase was determined. DSC experiments were also found in accord with mesophase formation. For the synthesis of N‐substituted polyaniline with these mesogen molecules, the emeraldine base polyaniline was reacted with BuLi to produce the N‐anionic polyaniline and then deprotonated polyaniline was reacted with bromine‐end mesogen to prepare mesogen‐substituted polyaniline through N‐substitution reaction. The degree of N‐substitution can be controlled by adjusting the molar feed ratio of mesogen to the number of repeat units of PANi. The microstructure and compositions of obtained polymers were characterized by FT‐IR, elemental analysis, DSC, and scanning electron microscopy (SEM). The cyclicvoltammetry show that the electroactivity of N‐substituted polyaniline is strongly dependent on the degree of N‐grafting. The solubility of mesogen‐substituted polyaniline in common organic solvents such as THF and chloroform was improved by increasing the degree of N‐substitution and also the samples are partially soluble in xylene. Liquid crystalline behavior of mesogen‐substituted polyanilines was investigated via POM, but no mesophase was observed. Copyright © 2008 John Wiley & Sons, Ltd.     

Effect of the dimeric H-bonded mesogens of chiral acids on the mesogenic and optical properties

A serial of chiral aromatic acid derivatives was systematically prepared to study the effect of dimeric H-bonded mesogens on liquid crystal (LC) and optical behaviours. The lateral fluoro-substituent and the chiral terminal chains were also studied for comparison. When the H-bonded mesogens changed from biphenyl or phenyl benzoate to naphthalene ring or benzene ring, the molecular length?width ratio reduced greatly, which thus led the temperature range of mesophases reduced and the phase transition decreased. The lateral fluoro-substituent, a shorter or meta-substituted terminal chain, could make the mesophase range narrowed or disappeared. Besides the chiral nematic (N*) phase, twist grain boundary C (TGBC*) phase was found in the double aromatic-ring acids with a chiral para-substituted octan-2-yloxyl group. Interestingly, the TGBC* phase could scatter away most incident light in any surface anchoring condition, and the light scattering performance exceeded any other phases of low-molecular-weight LCs known. The unusual H-boned material could be used for preparing reversible optical switches without using any polariser and any surface alignment treatment.     

Luminescent mesogen jacketed poly(1‐alkyne) bearing lateral terphenyl with hexyloxy tail

Mesogen jacketed liquid crystalline poly(1‐alkyne) and poly(1‐phenyl‐1‐alkyne) linked pendants of terphenyl mesogens with hexyloxy tails at the waist position (? {RC?C? [(CH₂)₃OOC‐terpheyl‐(OC₆H₁₃)₂]}_n? , where R?H, PHATP(OC6)2 ; R?C₆H₅, PPATP(OC6)2 ) were synthesized. The influences of structural variations on the thermal, mesomorphic, and luminescent properties were investigated. Polymerizations of all monomers are carried out by WCl₆‐Ph₄Sn catalysts successfully. The polymers are stable (T_d ≥ 340 °C) and soluble in common solvents. The monomers and polymers show enantiotropic SmA phases in the heating and cooling processes, and the lateral side chains of the mesogenic units are perpendicular to the main chain. The “jacket effect” of chromophoric terphenyl core “shell” around the main chain also contributes to polymers with high photoluminescence, and the pendant‐to‐backbone energy transfer path is involved in the luminescence process of this polymers. In comparison with monosubstituted polyacetylene PHATP(OC6)2 , the disubstituted polyacetylene PPATP(OC6)2 shows better photoluminescence in both THF solution and film, and exhibited about 40 nm red‐shifted than PHATP(OC6)2 , indicating that the “jacket effect” of terphenyl mesogens forces poly(1‐phenyl‐1‐alkyne) backbone to extend in a more planar conformation with a better conjugation. © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2010     

Infrared analysis of phase transitions in liquid crystal acrylate monomers bearing urethanic groups and cholesteryl as mesogen

An infrared analysis of phase transitions in three enantiotropic liquid crystalline acrylate monomers with different spacer lengths bearing urethane groups and cholesteryl as mesogen was carried out. Through heating and cooling, spectral modifications especially at the level of carbonyl, –NH– and urethane alkoxyl oxygen groups were found. These findings reveal the influence of hydrogen bonding on mesomorphic properties of the studied compounds mentioning that both liquid crystal transitions are evidenced by the spectral changes. For all the compounds studied, the values of the transition temperatures deduced from the spectral modifications are in good agreement with those obtained from DSC measurements.     

固相萃取-高效液相色谱法测定地表水中的苯并三唑和苯并噻唑

建立了固相萃取-高效液相色谱分析地表水中苯并噻唑、苯并三唑、5-甲基-苯并三唑、5-氯-苯并三唑及5,6-二甲基-苯并三唑的方法。地表水样品采用HLB固相萃取柱富集净化后,在甲醇-水(55:45, v/v)流动相中用ZORBAX SB-C18色谱柱(250 mm×4.6 mm, 5 μm)分离,紫外检测,外标法定量。结果表明,5种目标化合物在0.064～80 mg/L范围内均呈良好的线性关系,线性相关系数均大于0.9999,仪器检出限为1.9～3.2 μg/L。空白自来水样中的加标回收率为87.8%～125.6%,相对标准偏差(n=3)为0.4%～9.4%。应用该方法测定了大连自来水及辽河入海口水样,在辽河入海口地表水中检出苯并噻唑、苯并三唑、5-甲基-苯并三唑、5-氯-苯并三唑。     

Synthesis and optical behaviour of hydrogen-bonded liquid crystals based on a chiral pyridine derivative

Three series of cholesteryl-containing supramolecular hydrogen-bonded (H-bonded) liquid crystal (LC) complexes with different number of fluoro-substituent were synthesised and characterised. Cholesteryl isonicotinate as proton acceptor and 4-n-alkoxybenzoic acids with or without fluoro-substituent as proton donor had been mixed in tetrahydrofuran to obtain H-bonded LC complexes. The effect of lateral substitution and the length of terminal chain in the H-bonded precursors on the formation of the supramolecular complexes had been examined. It was found that the introduction of fluoro substituent on the induced mesogens could widen the molecular width and thus reduce the molecular aspect ratio of the complexes, therefore it could lead to compress the formation of the LCs. However, the fluoro substituent played a positive role in enhancing the intermolecular interactions and stabilising the H-bond structure of the complexes. The influence of terminal length on the mesogenic behaviours is also discussed. On increasing the spacer length, the clear point and the thermal range of induced mesophase-like cholesteric phase decreased, and an induced chiral smectic phase began to appear in some complexes with long terminal tails.     

Fast switching beam steering based on ferroelectric liquid crystal phase shutter and polarisation grating

We report on fast-switching and high-efficient optical beam steering based on a polymerisable liquid crystal polarisation grating (PG) in combination with ferroelectric liquid crystal (FLC) phase shutter. The PG was fabricated in a convenient single-step holographic exposure process using photo-sensitive azo-dye material as alignment layer for liquid crystal (LC) director. A binary electro-optical FLC was employed for circular polarisation selection, which enables the electro-tunable steering of the combined system. The efficiency of 95.7% with 82 μs switching time is obtained for 1064 nm laser. This work provides a versatile candidate for non-mechanical beam steering devices.     

Synthesis and curing of liquid crystalline epoxy resin based on naphthalene mesogen

Aromatic liquid crystalline epoxy resin (LCE) based on naphthalene mesogen was synthesized and cured with aromatic diamines to prepare heat‐resistant LCE networks. Diaminodiphenylester (DDE) and diaminodiphenylsulfone (DDS) were used as curing agents. The curing reaction and liquid crystalline phase of LCE were monitored, and mechanical and thermal properties of cured LCE network were also investigated. Curing and postcuring peaks were observed in dynamic DSC thermogram. LCE network cured with DDE displayed liquid crystalline phase in the curing temperature range between 183 and 260°C, while that cured with DDS formed one between 182 and 230°C. Glass transition temperature of cured LCE network was above 240°C, and crosslinked network was thermally stable up to 330°C. © 1999 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 37: 419–425, 1999     

在还原剂存在下CO2作为碳源合成苯并噻唑反应的研究进展

CO₂是一种来源丰富、价廉易得的C1资源。将CO₂高值化利用是“双碳”目标实现的途径之一。苯并噻唑类化合物广泛应用于医药、农药等领域。因此,从绿色和可持续发展角度来看,利用CO₂作为碳源合成杂环化合物苯并噻唑具有重要的意义。本文综述了氢气、硅烷和硼烷三类还原剂还原CO₂与邻氨基苯硫酚反应合成苯并噻唑的方法,分析了各种方法的优缺点,阐述了采用不同还原剂的反应机理,并指出了这一领域面临的问题。另外,对该领域未来的发展方向进行了展望,如绿色环保溶剂的使用、新型高效还原剂的研究、苯并噻唑新合成路线的设计等。     

Time‐dependent deformation of structurally chiral polymer networks in stabilized cholesteric liquid crystals

Polymerization of crosslinkable liquid crystal monomers in chiral liquid crystalline media stabilizes the phase and enables distinct electro‐optic properties relative to small‐molecule analogs. Particularly interesting are cases where the polymerization forms a crosslinked polymer network that maintains a “structural” chirality. Recent reports have employed this methodology to realize a diverse set of electro‐optic responses in polymer stabilized cholesteric liquid crystals (PSCLCs) including reflection bandwidth broadening, reflection wavelength tuning, and dynamic scattering modes. It has been proposed that the mechanism at the root of these electro‐optic responses is an ion‐mediated, electromechanical deformation of the stabilizing and structurally chiral polymer network. In an effort to better understand the nature of these deformations, here we have characterized the electro‐optic response of PSCLCs with different polymer concentrations and crosslink densities. The dynamic response of PSCLCs to electric fields exhibits a time‐dependent behavior reminiscent of the creep of polymeric materials to mechanical deformations. The electro‐optic response can be described as the superposition of two contributions: the fast deformation of a relatively soft component of the polymer network (1–2 s) and the slower (10–20 s) deformation of a harder component. © 2018 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2018 , 56, 1087–1093     

Dielectric relaxation spectroscopy and electro-optical studies of a new,partially fluorinated orthoconic antiferroelectric liquid crystal material exhibiting V-shaped switching

In this paper we report the results from detailed electro-optical and dielectric studies in various antiferroelectric and ferroelectric phases of an orthoconic antiferroelectric liquid crystal (OAFLC) material . The material possesses high tilt and high spontaneous polarisation. Such an OAFLC, because of its high tilt, provides an excellent dark state. The material exhibits V-shaped switching in the SmC* phase. Dielectric studies reveal the existence of another phase during heating in the range between 78.6 and 92°C which did not appear in the DSC curve and in polarising microscopy. This phase has been identified as the SmC_γ* phase and is extremely sensitive with respect to the cell conditions, aligning material, purity, etc. Three dielectric modes have been assigned in the above-mentioned temperature range and their origins are discussed.     

Ferroelectric polymer nanocomposite alignment layer in twisted nematic liquid crystal devices for reducing switching voltage

Twisted nematic liquid crystal device (TNLCD) was fabricated using a ferroelectric zinc oxide (ZnO)-doped polyimide alignment layer. The ferroelectric nanoparticle can produce a local electric field, which can trigger the orientation of liquid crystal molecule and reduces the switching voltage. The uniform dispersion of ferroelectric ZnO nanoparticles in the alignment layer was studied using field emission scanning electron microscopy and atomic force microscopy. The ferroelectric property of ZnO-doped polyimide was investigated using dynamic contact electrostatic force microscopy. An increased local electric field due to the presence of nano ZnO was confirmed with the help of scanning tunnelling microscopy. An augmentation of capacitance was observed with an increase in concentration, which substantiates the reduction of switching voltage of TNLCD with the modification of ferroelectric nanoparticle-doped alignment layer.