Photoinduced alignment of polymerisable liquid crystals on photoreactive polymers containing 2,6-bis(benzylidene)-1-cyclohexanone units in the main chain

Photoreactive polymers containing 2,6-bis(benzylidene)-1-cyclohexanone (bisBC) units were synthesised and investigated as a photoalignment layer for polymerisable liquid crystals (PLCs) and liquid crystalline polymers (LCPs). The liquid crystalline materials were aligned homogeneously on the photoalignment layers in a wide range of irradiation dose of linearly polarised UV light (LPUVL). Specifically, for the photoalignment layer baked at 80°C, order parameters of the liquid crystalline materials were low due to the disturbance of oriented-photoreactive polymer caused by the contact with the solvent of liquid crystalline materials. However, the liquid crystalline materials were aligned homogeneously even at low irradiation doses on the thermally cured photoalignment layer baked at 180°C. In addition, the liquid crystalline materials were aligned perpendicular to the LPUVL electric field. The alignment mechanism is discussed by comparing the retardation of photoalignment layer with anisotropic polarisabilities of model molecules calculated by density functional theory (DFT). It is suggested that the liquid crystalline materials aligned along the unreacted chromophores in the photoreactive polymer.     

Polyfunctional intermediates for the preparation of liquid-crystalline and anisotropic materials

This paper describes the polyfunctional intermediates for the preparation of various anisotropic and liquid-crystalline compounds with different combinations of cyclic, bridge, terminal fragments and lateral substituents. Both chiral and nonchiral nematic, smectic mesomorphic and anisotropic compounds can be prepared by the transformations of the corresponding 3,6-disubstituted cyclohex-2-enones, trans-2,5-disubstituted cyclohexanones, 3,5-disubstitiuted 2-isoxazolines, substituted cyclohex-2-enonyl 2-isoxazolines, 1,2-disubstitiuted cyclopropanols and substituted unsaturated epoxyketones.     

Photo-induced alignment behaviour of polymerisable liquid crystals on bisazide in a polymer matrix

Photo-reactive bisazide in a polymer matrix containing acryloyl groups on the side chain was investigated as a photoalignment layer for polymerizable liquid crystals (PLC). We found the thin film of bisazide (2,6-bis(4-azidobenzylidene)-4-methyl-1-cyclohexanone) in a polymer matrix, irradiated by linearly polarised ultraviolet light (LPUVL), was able to homogeneously align PLC. The LPUVL irradiation dose changed the orientation direction of the PLC on the thin film of bisazide in the polymer matrix. In addition, the direction of the slow axis for the retardation of the photoalignment layer changed from parallel to perpendicular to the LPUVL electric field with the irradiation dose. From these results, it was suggested that the PLC was likely to be aligned along the slow axis of the retardation of the photoalignment layer. We concluded that the key mechanism that changed the direction of the slow axis in a plane was the photoreaction of azide–acrylate at low irradiation dose and that of bis(benzylidene)cyclohexanone at high irradiation dose. Although the photoalignment as a result of a simple photo cross-linking was previously little known except for photo-dimerisation, we revealed that the photoaddition of azide–acrylate is able to achieve the photoalignment.     

Photosensitivity,substituent and solvent-induced shifts in UV-visible absorption bands of naphthyl-ester liquid crystals: a comparative theoretical approach

The substituent- and solvent-induced shifts in UV-visible absorption bands of naphthyl-ester nematic liquid crystals, viz., 4-octylphenyl-6-octyloxy-2-naphthoate (NAPHE1) and 6-octyloxy-2-naphthylyl-4-octyloxybenzoate (NAPHE2), have been investigated using the DFT, CNDO/S and INDO/S methods. A correlation has been made between molecular charge distribution and phase stability based on Mulliken, Loewdin, AM1, PM3, MNDO, CNDO/S and INDO/S methods. The observed π→π* and n→π* electronic transitions have been reported. The substituent- and solvent-induced shifts in absorption bands, transition energies and energy gaps have been discussed. The photosensitivity of the molecules has been analysed based on these shifts. It has been observed that the substituent has a dominant role on both absorption maxima and energy band gap, whereas the solvent has a dominant role only on absorption maxima, and no effect has been observed on the energy gap. These shifts may provide beneficial consequences in determining the end use of compounds.     

Development of Liquid Crystalline Order During Cure of Mesogenic Epoxy Resins

In the present paper we describe the curing process of a new liquid crystalline epoxy monomer with 4,4′-diaminodiphenylenemethane (DDM). The characteristic of cured product is presented. Both the monomer and cured product have been characterized by IR and NMR spectroscopy, differential scanning calorimetry (DSC), polarized optical microscopy (POM), wide-angle X-ray scattering (WAXS) and dielectric relaxation spectroscopy (DRS).The curing process was analysed with the use of DSC and real-time DRS.     

In situ control of surface molecular order in liquid crystals using a localised polymer network and its application to electro-optical devices

A liquid crystal (LC) alignment technique has been developed that allows local control of the polar pretilt angle over the range of 0–90°. This was achieved through the formation of a polymer network localised in the vicinity of the LC cell substrates. The network was formed as a result of in situ UV-induced polymerisation of a photo-reactive monomer added at concentrations of 0.5–1%. Localisation of the polymer network at the LC–substrate boundary was achieved by the application of a high voltage before polymerisation. The resultant pretilt angle was determined by the voltage applied during the polymerisation and/or the duration of the voltage application before the polymerisation step. The desired pretilt angle could be set over a small area of the sample, which allows the fabrication of LC devices with spatially variable optical retardation. Using this method we fabricated a converging lens, a bi-prism, and a phase diffraction grating with resolution greater than 50 lines mm^?1.     

纳米氧化锆沉积棉花纤维的制备及其在磷酸化多肽快速富集中的应用

采用液相沉积法在棉花纤维的表面成功沉积了纳米氧化锆颗粒,并将其装填在移液枪的吸头内,通过移液枪的抽吸实现对磷酸化多肽的萃取,萃取过程只需要2 min,方法简单、快速。该材料不仅可以从β-酪蛋白酶解物这种简单的体系中萃取出9个磷酸化多肽,还可以从物质的量比为1∶100的β-酪蛋白酶解物和牛血清白蛋白（BSA）酶解物混合物这类含有大量非磷酸化多肽的复杂样品中萃取出4种磷酸化多肽,且没有非磷酸化多肽被检出,表现出较好的萃取选择性。将该材料应用于人血清和脱脂牛奶这两种复杂实际样品的酶解物中磷酸化多肽的快速富集萃取,分别检测出5种和9种磷酸化多肽,均表现出较好的选择性。     

Effects of humidity and surface on photoalignment of brilliant yellow

Controlling and optimising the alignment of liquid crystals is a crucial process for display application. Here, we investigate the effects of humidity and surface types on photoalignment of an azo-dye brilliant yellow (BY). Specifically, the effect of humidity on the photoalignment of BY was studied at the stage of substrate storage before coating, during the spin-coating process, between film coating and exposure, and after exposure. Surprising results are the drastic effect of humidity during the spin-coating process, the humidity annealing to increase the order of the BY layer after exposure and the dry annealing to stabilise the layer. Our results are interpreted in terms of the effect of water on the aggregation of BY. The type of surface studied had minimal effects. Thin BY films (about 3 nm thickness) were sensitive to the hydrophilicity of the surface while thick BY films (about 30 nm thickness) were not affected by changing the surface. The results of this paper allow for the optimisation of the BY photoalignment for liquid crystal display application as well as a better understanding of the BY photoalignment mechanism.     

Anisotropic derivatives of (-)-L-lactic acid and their nanocomposites

The paper describes the synthesis and physical-chemical properties of anisotropic derivatives of (-)-L-lactic acid and their nanocomposites. Anisotropic optically active aryl (S)-2-(ω-halogenalkoxy)lactates and (R)-2-aryloxypropionic acids have been synthesised by the modification of corresponding 3,6-disubstituted cyclohex-2-enones, (-) ethyl L-lactate and ethyl esters of (S)-2-(4-bromobutoxy)- and (S)-2-(6-bromohexyloxy)propionic acids. The optically active (R)-2-aryloxypropionic acids were used for the preparation of mesomorphic nanocomposite materials and their properties were studied. Anisotropic materials based on the derivatives of lactic acid are capable to interact with inorganic nanoparticles providing a tool for the creation of new nanocomposite materials.     

Liquid chromatography of phenolic compounds in natural water using on-line trace enrichment

Summary Two packing materials, C18 and PLRP-S, are studied for on-line trace enrichment of phenolic compounds in water. Various precolumns of different internal diameter are also tested and the addition of an ion-pair reagent to increase retention and thus, breakthrough volumes of phenolic compounds, is studied. Best results are obtained when a PLRP-S precolumn is coupled on-line with a C18 analytical column and DAD detector. Addition of TBA considerably increases breakthrough volumes. In contrast, when a C18 precolumn is used, breakthrough volumes are lower and it is impossible to determine TCP and PCP, under the experimental conditions used, because of interference of other nonpolar compounds in the samples. The performance of the system is evaluated with river and tap water and the preconcentration of 10 ml of sample in a PLRP-S precolumn involves a linear range between 1 g 1^–1 and 20 l^–1 and limits of determination between 0.5 g l^–1 and 1 g l^–1 are obtained.     

Trace enrichment of polar pollutants from water and the influence of humic substances

Summary A practical liquid chromatographic early-warning system for polar pollutants in water ought to have detection limits at a level below a microgram per litre. Using ultraviolet absorbance detection this normally necessitates trace enrichment of the samples. In this study ten different sorbents have been tested with respect to their enrichment capacity. The hydrophobic polymeric PLRP-S material, in combination with a C-18 modified analytical column, proved to be the best choice. The influence of humic substances, present in surface water, was also studied. Lowering of the sample pH, resulted in a significant increase in the interferences due to the humic substances.     

Engineered Anisotropic Fluids of Rare-Earth Nanomaterials

The self-assembly of inorganic nanoparticles into well-ordered structures in the absence of solvents is generally hindered by van der Waals forces, leading to random aggregates between them. To address the problem, we functionalized rigid rare-earth (RE) nanoparticles with a layer of flexible polymers by electrostatic complexation. Consequently, an ordered and solvent-free liquid crystal (LC) state of RE nanoparticles was realized. The RE nanomaterials including nanospheres, nanorods, nanodiscs, microprisms, and nanowires all show a typical nematic LC phase with one-dimensional orientational order, while their microstructures strongly depend on the particles’ shape and size. Interestingly, the solvent-free thermotropic LCs possess an extremely wide temperature range from −40 °C to 200 °C. The intrinsic ordering and fluidity endow anisotropic luminescence properties in the system of shearing-aligned RE LCs, offering potential applications in anisotropic optical micro-devices.     

Engineered Anisotropic Fluids of Rare‐Earth Nanomaterials

The self‐assembly of inorganic nanoparticles into well‐ordered structures in the absence of solvents is generally hindered by van der Waals forces, leading to random aggregates between them. To address the problem, we functionalized rigid rare‐earth (RE) nanoparticles with a layer of flexible polymers by electrostatic complexation. Consequently, an ordered and solvent‐free liquid crystal (LC) state of RE nanoparticles was realized. The RE nanomaterials including nanospheres, nanorods, nanodiscs, microprisms, and nanowires all show a typical nematic LC phase with one‐dimensional orientational order, while their microstructures strongly depend on the particles’ shape and size. Interestingly, the solvent‐free thermotropic LCs possess an extremely wide temperature range from ?40 °C to 200 °C. The intrinsic ordering and fluidity endow anisotropic luminescence properties in the system of shearing‐aligned RE LCs, offering potential applications in anisotropic optical micro‐devices.     

纤维素及其衍生物液晶研究新进展

本文全面地综述了纤维素及其衍生物溶致性液晶和热致性液晶的形成, 液晶性与大分子链结构, 以及具有胆甾型液晶相结构的纤维素衍生物复合材料等方面的最新研究进展。     

Click novel glycosyl amino acid hydrophilic interaction chromatography stationary phase and its application in enrichment of glycopeptides

A novel glycosyl amino acid hydrophilic interaction chromatography (HILIC) stationary phase was prepared via click chemistry. The key intermediate N₃-glycosyl d-phenylglycine was prepared by a three steps procedure, including selective condensation of amino glucose with N-succinimidyl ester of Boc-d-phenylglycine, deprotection and transformation of amino group to azido group. The structure of all the intermediates and functionalized silica beads were confirmed by ¹H NMR, IR, elemental analysis and ¹³C CP-MAS. The chromatography test showed that this new type of separation material possessed good HILIC properties and glycopeptide enrichment characteristics. Nucleosides and bases could be separated in a simple eluent composition (only acetonitrile in combined with water), and with the same condition, these model compounds could not be separated on the commercial HILIC column (Atlantis). Click glycosyl amino acid thus prepared also showed longer retention and better separation ability in the separation of polar organic acids.     

纤维素及其衍生物液晶研究近况

就纤维素及其衍生物溶性液晶和热致性液晶的液晶性及其影响因素,和流变性能等方面的研究作了较为详尽的综述。     

The birefringence and extinction coefficient of positive and negative liquid crystals in the terahertz range

Birefringence and extinction coefficients of positive nematic liquid crystal (NLC) MLC-2142 and negative NLC BHR28000-400 are measured by terahertz time-domain spectroscopy system (THz-TDS). Frequency ranging from 0.1 to 0.6 THz, the birefringence of positive NLC MLC-2142 increases with the increase of frequency, and keeps larger than 0.23, which exhibits application potential in tunable broadband LC THz device where a large birefringence is required. In contrast, the birefringence of BHR28000-400 decreases with the increased frequency, which shows a completely different optical property from the positive NLC. The extinction coefficient of the above two kinds of liquid crystals are also investigated.