Aliphatic acid esters of (2-hydroxypropyl) cellulose—Effect of side chain length on properties of cholesteric liquid crystals

A series of aliphatic acid esters of (2-hydroxypropyl) cellulose (C_nPC) were synthesized via the esterification of aliphatic acid chloride and (2-hydroxypropyl) cellulose (HPC). The liquid crystalline (LC) phases and transitions were investigated using differential scanning calorimetry, wide-angle X-ray diffraction (WAXD), and polarized light microscope (PLM) techniques. This series of C_nPC polymers exhibited characteristic features of cholesteric LC phases between their glass transition and isotropization temperatures. The cholesteric LC characteristics were studied utilizing an ultraviolet/visible/near infrared spectrometer in a reflection mode. It was confirmed that, with an increase in the number of methylene units in the side chains of this series of C_nPC polymers, there was an increase, on the scale of nanometers, in the layer spacing values for the cholesteric LC phases measured by WAXD. This periodic layer spacing represents the thickness of the neighboring twisted layers in a helical structure. Based on a unique significant red shift of the maximum reflection peak for the LC phases in this series of C_nPCs, it is evident that the pitch distance in the helical structure also increases with an increase in the length of methylene units in the side chains.     

Preparation and thermal properties of liquid crystalline ionomers having mesogenic ester side chains containing three phenyl groups

A series of liquid crystalline (LC) copolymers having both the repeat units of mesogenic ester side chains containing three phenyl groups and the repeat units possessing an acid group were prepared. The acid groups of the LC copolymers were neutralized with sodium acetate to give a varying degree of neutralization. It was found that the LC properties of the ionomers depended strongly on both the relative amount of the units having the mesogenic side chains and the amount of ionic units. It was also observed that the formation of the nematic phase of the LC ionomers was suppressed by the increase in ion contents. After the analysis of the thermal data of the phase transitions, it was suggested that the transition temperatures of the LC phases of the copolymers and their ionomer forms, and the temperature ranges for the LC phases were affected by the relative amounts of both mesogenic and acidic units and by the degree of neutralization, simultaneously.     

Curcumin Remedies Testicular Function and Spermatogenesis in Male Mice with Low-Carbohydrate-Diet-Induced Metabolic Dysfunction

Increasing reports on the significance of dietary patterns in reproduction have arisen from both animal and human studies, suggesting an interactive association between nutrition and male fertility. The aim of this study was to investigate the effects of curcumin supplementation on low-carbohydrate-diet-induced metabolic dysfunction, testicular antioxidant capacity, apoptosis, inflammation and spermatogenesis in male mice. Male C57BL/6 mice were fed a normal diet (AIN-93M group, n = 12) and a low-carbohydrate diet for 12 weeks (LC group, fed with low-carbohydrate diet, n = 48), and mice randomly chosen from the LC group were later fed their original diet (LC group, n = 12). This diet was changed to AIN-93M feed (LC/AIN-93M group, n = 12), a ketogenic diet (LC/KD group, n = 12), or a ketogenic diet treated with curcumin supplementation for the final 6 weeks (LC/KDCu group, n = 12). A poor sperm morphology and mean testicular biopsy score (MTBS) were observed in the LC and LC/KD groups, but they were eliminated by the normal diet or ketogenic diet with curcumin. The LC group exhibited a lower testicular testosterone level and a lower 17β-HSD activity and protein expression. This also enhanced apoptosis protein expressions in testis tissue, including Bax/BCl₂, cleaved caspase 3, PARP and NF-κB. Meanwhile, we found a statistically significant increase in lipid peroxidation and decreased superoxide dismutase (SOD), catalase (CAT) and glutathione peroxidase levels in the LC group. Our study indicated that a replacement of a normal diet or ketogenic diet supplemented with curcumin attenuated poor semen quality and reduced testosterone levels by the LC diet by reducing oxidative stress.     

带双甲基丙烯酰基偶氮苯液晶化合物的合成与表征

合成了一毓新的带双甲基丙烯酰基偶氮苯液晶化合物，并利用元素分析、红外光谱、核磁共振谱及热台偏光显微镜等方法对其进行了不征。     

Elution factors of synthetic oxotriacylglycerols as an aid in identification of peroxidized natural triacylglycerols by reverse-phase high-performance liquid chromatography with electrospray mass spectrometry

Selected elution factors were determined for model oxotriacylglycerols as an aid in identification of the peroxidation products of natural triacylglycerols by reverse-phase high-performance liquid chromatography (HPLC) with electrospray mass spectrometry (LC/ES/MS). For this purpose synthetic triacylglycerols of known structure were converted to hydroperoxides, hydroxides, epoxides, and core aldehydes and their dinitrophenylhydrazones by published procedures. The oxotriacylglycerols were resolved by normal-phase thin-layer chromatography and reverse-phase HPLC, and the identities of the oxotriacylglycerols confirmed by LC/ES/MS. Elution factors of oxotriacylglycerols were determined in relation to a homologous series of saturated triacylglycerols, ranging from 24 to 54 acylcarbons, and analyzed by reverse-phase HPLC, using a gradient of 20–80% isopropanol in methanol as eluting solvent and an evaporative light-scattering detector. It was shown that the elution times varied with the nature of the functional group and its regiolocation in the triacylglycerol molecule. A total of 31 incremental elution factors were calculated from chromatography of 33 oxygenated and nonoxygenated triacylglycerol species, ranging in carbon number from 36 to 54 and in double-bond number from 0 to 6.     

Dimeric liquid crystalline thermosets from azo-containing diglycidyl ether cured by anhydride

A series of dimeric liquid crystalline (LC) epoxy monomers containing azobenzene group with central spacers of different lengths were synthesized and structurally characterized by ¹H NMR, ¹³C NMR, and elemental analysis. The mesogenic behavior of these monomers was measured by differential scanning calorimetry (DSC), polarized optical microscopy (POM), and X-ray diffraction (XRD). Like other dimeric LC epoxy monomers, the melting points, clear points, and mesophase of these compounds are influenced by the carbon numbers of central spacers. Anhydride was employed to cure the monomers and LCTs with nematic phase were obtained. Thermal properties, dynamic mechanical properties and UV–Vis spectra of the LCTs were studied. The decomposition of the LCTs occurred near 220 °C and followed three stages. The LCTs also had the natural absorbance bonds of azo compounds.     

Liquid-crystalline elastomers produced by chemical crosslinking agents containing sulfonic acid groups

A series of siloxane-based liquid-crystalline (LC) elastomers were synthesized by using chemical crosslinking agents containing sulfonic acid groups. The crosslink densities of the elastomers were determined by swelling experiments. Two kinds of melting temperature corresponding to crystallization of siloxane matrix and crystallization of LC segments were clearly detected. Some of the polymers exhibited smectic mesophase textures or cholesteric mesophase textures. A proposed model containing LC segment structure and ionic crosslinking lamellar structure separated by siloxane chains was given. The ion aggregated in domains forces the siloxane chains to fold and form an irregular lamellar structure. Ionic aggregates and LC segments may be dispersed each other to form multiple blocks with increasing ionic crosslinking content.     

Synthesis and improved mechanical properties of twin-mesogenic epoxy thermosets using siloxane spacers with different lengths

A series of twin-mesogenic epoxy resins with siloxane (di-, tri-, and tetra-siloxane) chain spacers of different lengths were successfully synthesized. Results showed that the melting point of the twin-mesogenic epoxy monomers decrease by more than 50 °C due to the change of siloxane spacer length. In particular, the tri- and tetra-incorporated siloxane twin-mesogenic epoxy monomers showed a liquid crystalline (LC) phase below 100 °C during the cooling process. Epoxy thermosets with isotropic and smectic (S_m) LC phases were then prepared using an aromatic amine and the dependence on curing temperature was investigated. Furthermore, the relationship between the ordered network chain structure and mechanical properties was investigated. Results were compared with isotropic and S_m LC phases. The tensile strain and fracture energy in the S_m type LC thermosets increased without a decrease in the tensile modulus, and this occurred in all systems irrespective of siloxane spacer length. The maximum value of the fracture energy (283 kJ m⁻²) reached by LC thermosets with increased spacer lengths was twice as large as that using the alkyl chain spacer (144 kJ m⁻²). © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019 , 136, 47891.     

Liquid crystalline polyesters by staged-addition polycondensation

Summary A series of model liquid crystalline (LC) polyesters have been prepared by low temperature solution polycondensation using staged addition methods. The model thermotropic polyesters were composed of aliphatic spacers and mesogenic groups made from substituted terephthalic acid and methyl hydroquinone. Both the mesogenic groups and the spacers were placed in the main chain. Attractive properties of these polymers include solubility in many organic solvents such as THF and DMSO with softening temperatures below 150°C. Some of these polymers show no melting transitions, and depending on the terephthalate group substituent, either smectic or nematic phases are formed. Results from GPC analysis show good solubility of polymers in THF with M_w lower than 10,000 compared to polystyrene standards. The synthesis and characterization of these LC polyesters are reported here.     

Main‐chain liquid‐crystalline ionomers bearing potassium sulfonate groups

A series of thermotropic main‐chain liquid‐crystalline (LC) ionomers were prepared, which contained potassium sulfonate groups pendent to the chains. The polymers were prepared in an esterifying reaction with potassium ion contents ranging between 0 and 3.9 wt %. The content of potassium ion was characterized by spectrophotometric analysis with sodium tetraphenylboron as the titrant. Chemical structures were determined by various experimental techniques including Fourier transform IR spectroscopy and ¹H‐NMR. LC properties were characterized by differential scanning calorimetry, polarizing optical microscopy, and X‐rays. All of the polymers displayed nematic or smectic mesophases. With increasing potassium sulfonate ionic concentration in the polymers, the melting temperatures and isotropic transition temperatures changed little, whereas the temperature of the smectic A–nematic phase transition increased. The ionic aggregation was tangled with the rigid mesogenic groups of LC segments to form multiple block domains, leading the soft main chains to fold and form a lamellar structure due to their electrostatic interactions. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 96: 2021–2026, 2005     

亚致死浓度氟啶虫胺腈对桃蚜体内能量物质的影响

[目的]明确氟啶虫胺腈亚致死浓度对桃蚜体内能量物质的影响,旨在为氟啶虫胺腈对靶标害虫的解毒代谢机理提供更多的理论参考.[方法]通过GC-MS分析法,测定氟啶虫胺腈亚致死浓度(LC10和LC30)胁迫下,桃蚜体内脂肪酸、氨基酸及可溶性糖的组成及含量变化.[结果]氟啶虫胺腈亚致死浓度作用下,桃蚜体内的总脂肪酸含量显著降低,...     

Display forming polymer/liquid crystal composite layers and their stability against external mechanical distortions

The liquid crystal display (LCD) technology is confronted with the task to substitute rigid glass plates enclosing the electro‐optically active liquid crystal (LC) material by plastic substrates. In particular, the commercialization of flexible displays requires a sufficient stabilization against external mechanical distortions. To achieve LC layer stabilization, several procedures have been suggested. In this work, the thermal‐induced phase separation (TIPS) technique has been applied to generate composite films consisting of LC compartments which are encased by coherent polymer walls after binodal phase separation. Composite films were prepared from a series of poly(methacrylates) and various commercial nematic LC mixtures. Furthermore, the use of copolymers as well as binary blends from “hard” and “soft” poly(methacrylates) broadens the possibilities to control the film morphology. To compare different polymer/LC composite films regarding their stability under compression load, the samples were investigated by indentation tests using an inverse reflected‐light microscope combined with a digital image acquisition technique. The deformation of the composite layers was evaluated by the uniDAC image analysis which relies on the more general method of Digital Image Correlation (DIC). Some of the fabricated composites show a remarkably high indentation resistance, especially such prepared from poly(1‐tetralyl methacrylate) and poly(4‐tert‐butylcyclohexyl methacrylate). The results facilitate the selection of suitable composite systems for the fabrication of mechanically stabilized flexible LC displays. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

Effect of nano‐silica filler on the rheological and morphological properties of polypropylene/liquid‐crystalline polymer blends

A fumed hydrophilic nano‐silica‐filled polypropylene (PP) composite was blended with a liquid‐crystalline polymer (LCP; Rodrun LC5000). The preblended polymer blend was extruded through a capillary die; this was followed by a series of rheological and morphological characterizations. The viscosity of the PP matrix increased with the addition of the hydrophilic nano‐silica. At shear rates between 50 and 200 s^?1, the composite displays marked shear‐thinning characteristics. However, the incorporation of LC5000 in the PP composite eliminated the shear‐thinning characteristic, which suggests that LC5000 destroyed the agglomerated nano‐silica network in the PP matrix. Although the viscosity ratio of LCP/PP was reduced after the addition of nano‐silica fillers, the LCP phases existed as droplets and ellipsoids. The nano‐silicas were concentrated in the LC5000 phase, which hindered the formation of LCP fibers when processed at high shear deformation. We carried out surface modification of the hydrophilic nano‐silica to investigate the effect of modified nano‐silica (M‐silica) on the morphology of the PP/LC5000 blend system. Ethanol was successfully grafted onto the nano‐silica surface with a controlled grafting ratio. The viscosity was reduced for PP filled with ethanol‐M‐silica when compared to the system filled with untreated hydrophilic nano‐silica. The LC5000 in the (PP/M‐silica)/LC5000 blend existed mainly in the form of fibrils. At high shear rates (e.g., 3000 s^?1), the LC5000 fibril network was formed at the skin region of the extrudates. The exclusion of nano‐silica in the LC5000 phase and the increased viscosity of the matrix were responsible for the morphological changes of the LCP phase. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 87: 1484–1492, 2003     

Polyimide blend alignment layers for control of liquid crystal pretilt angle through baking

Polyimide films were used for liquid crystal (LC) alignment layers to control LC pretilt angles over the full range (8°-90°). The pretilt angles could be controlled using polyimide films prepared from polyamic acid for vertical LC alignment and using polyimide blend films prepared from two types of polyamic acids, one for vertical LC alignment and the other for planar LC alignment, by changing the baking times ranging from 40 to 180 min at 230 °C. The polyimide blend film could control the pretilt angle better than the polyimide prepared from just one polymer component. The LC alignment behavior was well correlated with the wettability of the polyimide films due to the fragmentation of the long alkyl side group on the polyimide surfaces by the baking process.     

Distinct Mechanisms for Processing Autophagy Protein LC3-PE by RavZ and ATG4B

Autophagy is a conserved catabolic process involved in the elimination of proteins, organelles and pathogens in eukaryotic cells. Lipidated LC3 proteins that are conjugated to phosphatidylethanolamine (PE) play a key role in autophagosome biogenesis. Endogenous ATG4-mediated deconjugation of LC3-PE is required for LC3 recycling. However, the Legionella effector RavZ irreversibly deconjugates LC3-PE to inhibit autophagy. It is not clear how ATG4 and RavZ process LC3-PE with distinct modes. Herein, a series of semisynthetic LC3-PE proteins containing C-terminal mutations or insertions were used to investigate the relationship of the C-terminal structure of LC3-PE with ATG4/RavZ-mediated deconjugation. Using a combination of molecular docking and biochemical assays, we found that Gln116, Phe119 and Gly120 of LC3-PE are required for cleavage by both RavZ and ATG4B, whereas Glu117(LC3) is specific to cleavage by RavZ. The molecular ruler mechanism exists in the active site of ATG4B, but not in RavZ. Met63 and Gln64 at the active site of RavZ are involved in accommodating LC3 C-terminal motif. Our findings show that the distinct binding modes of the LC3 C-terminal motif (116–120) with ATG4 and RavZ might determine the specificity of cleavage site.     

Mesomomorphism enhancement of modified side‐chain liquid‐crystalline polysiloxanes by copolymerization

The liquid‐crystalline (LC) monomer 4‐allyoxybenzoyloxy‐4′‐buthylbenzoyloxy‐p‐phenyl (M₁), whose LC phase appeared at lower temperatures, from 137 to 227°C, and the modified mesogenic monomer 4‐allyoxybenzoyloxy‐4′‐methyloxybenzoyloxy‐p‐biphenyl (M₂), whose LC phase appeared at higher temperatures, from 185 to 312°C, were prepared. A series of side‐chain LC polysiloxanes containing M₁ and M₂ were prepared by graft copolymerization. Their LC properties were characterized by differential scanning calorimetry, thermogravimetric analysis, polarizing optical microscopy, and X‐ray diffraction. The results show that the introduction of the modified mesogenic monomer M₂ into the polymeric structure caused an additional increase in the clearing point (isotropic transition temperature) of the corresponding polysiloxanes, compared with unmodified polysiloxanes, but did not significantly affect the glass‐transition temperature. Moreover, the modified polysiloxanes exhibited nematic phases as the unmodified polymer did. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 97: 1196–1201, 2005     

Synthesis and characterization of side‐chain cholesteric liquid‐crystalline polysiloxanes containing different space groups

A series of liquid‐crystalline (LC) polysiloxanes were synthesized by two different cholesteric monomers, cholest‐5‐en‐3‐ol(3β)‐10‐undecenoate and cholesteryloxycarbonylmethyl 4‐allyloxybenzoate. The chemical structures and LC properties of the monomers and polymers were characterized by various experimental techniques, including Fourier transform infrared spectroscopy, ¹H‐NMR, elemental analysis, differential scanning calorimetry, and polarized optical microscopy. The specific rotation absolute values increased with increasing rigid spacers between the main chain and the mesogens. All of the polymers exhibited thermotropic LC properties and revealed cholesteric phases with very wide mesophase temperature ranges. With a reduction in the soft‐space groups in the series of polymers, the glass‐transition temperature and the isotropic temperature increased slightly on heating cycles. Reflection spectra of the cholesteric mesophase of the series of polymers showed that the reflected wavelength shifted to short wavelengths with decreasing soft‐space groups in the polymers systems, which suggested that the helical pitch became shorter with increasing rigid‐space groups. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

Preparation and thermal characterisation of some new liquid crystalline copolymers involving a spacer unit based on vinylacetic acid

Summary Three series of new liquid crystalline (LC) copolymers having a polysiloxane backbone and two different mesogenic pendant groups, one involving a vinylacetic acid moiety in the spacer, have been synthesised. Thermal characterisation of these polymeers has allowed comparison of behaviour between a number of different copolymer systems. It was found that increasing amounts of the vinylacetic acid moiety lowered the clearing points (T_i) of the copolymers in an almost linear fashion whilst also inhibiting crystallinity in these polymers.     

Binders for higher-solids coatings. IV. Liquid–crystalline acrylic lacquers

A previously reported synthetic procedure was used to graft oligo-p-hydroxybenzoic acid (oligo-PHBA) to COOH-functional acrylic copolymers. Most of the products were side-chain LC copolymers. Length of the mesogenic oligo-PHBA groups averaged up to five aromatic rings per group. Because these long mesogenic groups have a strong tendency to form LC domains, it was possible to prepare LC side-chain copolymers having as little as 5 mol % of mesogenic monomer. Thus this synthetic procedure provides a versatile route for exploration of the properties of LC copolymers having relatively few but especially effective mesogenic groups. The potential utility of such LC copolymers as binders for nonbake coatings was assessed. Variables studied were molecular weight and T_g of the acrylic copolymer backbone, number and average length of oligo-PHBA segments, and the presence or absence of a flexible spacer between the acrylic backbone and the PHBA segments. Optimum LC copolymers have moderate (15,000–30,000) M_n, low (?10°C) backbone T_g, and low (5–7.5 mol %) population of long (5 PHBA units) oligo-PHBA units. Such copolymers have two major advantages as coatings binders: They form concentrated, stable, low-viscosity dispersions in common solvents, a very desirable characteristic for application. Coating films have excellent adhesion to metal, and they have an extraordinary combination of hardness (H–2H) and impact resistance (> 80 in. Ib). These properties are key indicators of coating performance and indicate that LC copolymers have excellent potential for use as binders for nonbake coatings. Other properties remain to be investigated.     

Synthesis of side group liquid crystal-coil triblock copolymers with cyanobiphenyl moieties and PEG as coil segments by atom-transfer radical polymerization and their thermotropic phase behavior

Summary A series of side group liquid crystal-coil(SGLC-coil) triblock copolymers with narrow polydispersity was synthesized by atom transfer radical polymerization (ATRP), which was designed to have LC conformation of poly(11-(4′-cyanophenyl-4″-phenoxy)undecyl methacrylate) and coil-conformation of polyethylene glycol (PEG) (Mn=6000) segment. The SGLC block was prepared with a rang of molecular weights from 3.5×10³ to 1.4×10⁴. The macro-initiator PEG6000-Br was synthesized with PEG and 2-Bromo-2-methylpropionyl bromide by reaction of acid bromide. Their characterization was investigated using proton nuclear magnetic resonance (¹H NMR), Fourier Transform Infrared (FT-IR) spectra, gel permeation chromatograph (GPC), differential scanning calorimetry (DSC) and polarized optical microscope (POM). All the block polymers exhibited a smectic A mesophase. The phase transition temperatures of the smectic to isotropic (T_S-T_I) phase increased and the crystallizability of PEG depressed with increasing of the molecular weight of the LC block. Received: 12 March 2002/Revised version: 25 April 2002/ Accepted: 30 April 2002