Unsaturated Carbon-carbon Double Bond Research Articles

A discovery for phosphorus valence and unsaturated bonds in polyphosphate/polyphosphonate: Promotion or inhibition for its flame-retardant mode of action in PET

Four polyphosphate/polyphosphonate flame retardants (PAP, POP, PAP-UB and POP-UB) have been designed and synthesized to study the effects of phosphorus valence states and the presence of unsaturated carbon-carbon double bonds on self-cross-linking impacting flame-retardant modes of action. It was found that phosphorus valence states affect the proportion of flame-retardant activity between the gas phase and condensed phase. A phosphonate containing +3-valence phosphorus is primarily effective as a gas-phase flame-retardant, while the one containing +5-valence phosphorus mainly exerted an impact in the condensed phase. The introduction of an unsaturated bond enhances the carbon-forming effect promoted by polyphosphates/polyphosphonates in a degrading polymer matrix and increases the melt viscosity for blends at high temperature. The phosphorus-containing fragments which might have been released into the gas phase are locked in the condensed phase due to CC bonds cross-linking, thus forming more high-quality phosphorus-rich char layers. This effect balances the distribution of gas-phase and condense-phase flame-retardant effects and is especially obvious in PET/polyphosphonate blends containing +3-valence phosphorus, which originally plays mainly the role of a gas-phase flame retardant. PET blends containing unsaturated carbon-carbon double bonds display better carbon formation, flame-retardant activity and anti-dripping behavior than these do without this feature.

(Digital Presentation) Renewable Itaconic Acid As a Cathode Additive Stabilizing Ni-Rich Layered Cathode Materials for Lithium-Ion Batteries

Renewable materials applied in lithium-ion batteries industry has obvious advantages because of its wide range of sources and low cost. The residual lithium compounds on the surface of nickel-rich LiNi1-x-yCoxMnyO2 (Ni-rich NCM) cathodes hinder its large-scale industrial application in lithium-ion batteries. In the past, researchers proposed several approaches including coating (Al2O3, Li3PO4), water washing coupling heat treatment. These conventional approaches have been found beneficial for mitigating the residual lithium and improving electrochemical performance of high rich nickel cathode. However, most of these used conventional additions are non-renewable precious metal or salt accompanied by extra processing/handling costs. More seriously, layer Ni-rich NCM cathodes cost more than lithium iron phosphate, because transition nickel salt is expensive. Obviously, it is crucial for Ni-rich NCM cathodes to develop green and low-cost modification process.In this work, renewable itaconic acid (IA) as a cathode addition is used to convert the residual lithium on the Ni-rich NCM cathodes into sacrificial organic lithium salts containing polar carboxylic acid and unsaturated carbon-carbon double bond to build the Li conductive cathode-electrolyte interphase (CEI) rich in organic component containing polycarbonates/polymeric specie during the electrochemical process. As a result, the capacity of the 0.5wt% IA modified NCM cathode retains 94.1 % after 90 cycles. Itaconic anhydride, an important renewable resource, is widely used in food processing and other fields because of its wide range of sources and low price. As such, our work proposes a practical approach to mitigates residual lithium issue and control CEI formation, developing high energy and long spans lithium-ion batteries by utilizing cheap and renewable organic acid. Figure 1

Small change, big impact: Simply changing the substitute on Si atom towards significant improvement of flame retardancy and toughness of epoxy resins

Enhancing simultaneously the flame retardancy and mechanical properties of polymer materials is a good expectation but always a tough challenge. In this work, two multifunctional compounds: phosphaphenanthrene/vinylsiloxane (DDVS) and phosphaphenanthrene/phenylsiloxane (DDPS) were synthesized, and both effectively improved the flame-retardant properties, toughness and UV shielding performance of epoxy resins (EPs) with high transparency. It was further found that the flame retardancy and toughness of EPs were greatly affected by simply changing the substituents from phenyl to vinyl groups on Si atom. Compared with DDPS, DDVS with vinyl group on Si showed more efficiency in improving flame retardancy (higher LOI value), self-extinguishing properties (higher UL 94 grade) and higher quality retention (more carbon residue) in EP. For example, DDVS was added in two-thirds of the amount of DDPS to make EPs achieve UL94 V-0 rating. This attributed to the high-temperature self-crosslinking of unsaturated carbon-carbon double bonds in DDVS, which can increase the charring ability of EPs and form more high-temperature stable char residues. Meantime, this also inhibited the release of volatile phosphorus-containing pieces from DDVS decomposition and retained more P in condense phase, thus improving the compactness and graphitization degree of char layers. The introduction of unsaturated bonds strengthened the condense-phase flame-retardant function of DDVS in EP, while retaining the original gas-phase flame-retardant actions of DOPO groups. The mechanism of gas-phase and condensed-phase mechanisms cooperated with each other, obtaining better flame retardant effect. Meanwhile, DDVS possessed greater efficiency than DDPS in increasing the fracture toughness of matrix due to the difference of steric hindrance between the substituents on silicon. Furthermore, the introduction of DDVS and DDPS did not significantly affect the transparency of EPs and the high visual transparency of materials was still maintained. In brief, the coordination design of phosphaphenanthrene and vinylsiloxane groups provided a theoretical basis to simultaneously improve the flame retardancy and toughening of EPs without losing glass transition temperature, while maintaining the high visual transparency of EPs with good UV shielding performance.

A novel colorimetric and red-emitting fluorescent probe based on benzopyrylium derivatives for selective detection and imaging of SO2 derivatives in cells and zebrafish

Abnormal levels of endogenous sulfur dioxide in organisms will cause cardiovascular, respiratory and neurological diseases. Therefore, the development of an effective detecting method for real-time, quantitative detection of sulfur dioxide derivatives in organisms is of great importance in physiological and pathological aspects. In this work, a red-emitting SO2 fluorescent probe based on benzopyrylium derivatives were designed and synthesized to specifically detect SO2 derivatives by nucleophilic addition of unsaturated carbon-carbon double bonds. The probe is characterized with rapid response, “naked eye” visualization, broad detection range and high sensitivity (8.1 μM) for SO2 derivatives. In addition, it has been applied to track the dynamic, real-time, visual detection of exogenous and endogenous SO2 in cells, and imaging of exogenous SO2 derivatives in zebrafish.

(Digital Presentation) Phosphonium Salts As Potential Guest Substances for Ionic Semiclathrate Hydrates

Semiclathrate hydrates (SCHs) are ionic crystalline compounds consisting of an organic guest cation in several cages formed by hydrogen bonding of water1. SCHs have recently been considered for application to air conditioning systems and refrigeration systems since desirable equilibrium temperatures and the considerable decomposition enthalpies are observed in the solid-liquid equillibria2. Ionic guest substances of SCHs include quaternary onium compounds such as tetrabutylammonium2 and tetrabutylphosphonium based salts3. We report here the preparation and thermodynamic properties of SCHs based on quaternary phosphonium bromides containing an unsaturated carbon-carbon double bond, as shown in Fig. 1, in comparison with the conventional saturated phosphonium salt, such as tetrabutylphosphonium bromide (P4444-Br).The unsaturated phosphonium bromides (P444(1All)-Br and P444(2All)-Br) were synthesized by quaternarization reaction of tributylphosphine with alkenyl bromides in a nitrogen atmosphere. The aqueous solutions were prepared from 5 to 50 w/w %. After thorough stirring, the aqueous solutions were cooled in a freezer to form SCHs. The SCHs were immersed into a thermostatic bath at 268 K for at least 1 day. The temperature in the thermostatic bath was raised from 268 K at a rate of 0.1 K/step (1 step: more than 5 h). The equilibrium temperatures were defined as the temperature at which SCHs were completely dissolved. The ionic crystal structure was analyzed by a powder X-ray diffraction (PXRD) technique, the dissociation enthalpy was measured by a micro differential scanning calorimeter (μDSC).Fig. 2 depicts the solid-liquid phase equilibrium diagram representing the phase equilibrium temperatures of SCHs. The equilibrium temperature of P444(1All)-Br SCH was higher than P4444-Br SCH. These results might be due to the steric effect of alkenyl group. As shown in Fig. 3, the ionic crystal structure of both P444(1All)-Br and P444(All)-Br SCHs were orthorhombic. The dissociation enthalpy of P444(1All)-Br SCHs and P444(2All)-Br SCHs were 188 J/g and 199 J/g, respectively. The unsaturated phosphonium bromides would be regarded as potential guest substances used for latent heat storage materials in air conditioning systems.References M. Oshima, et al, J. Chem. Thermodynamics, 90, 277 (2015).H. Oyama, et al, Fluid Phase Equilibria, 234, 131 (2005).J. Shimada, et al, Chem. Eng. Sci., 236, 116514 (2021). Figure 1

Multifunctional organosilicon compound contributes to stable operation of high-voltage lithium metal batteries

With the increasing demand for high-energy–density energy storage devices, lithium metal batteries have rekindled the interest of researchers due to ultra-high specific capacity. However, the extremely unstable interfaces between the electrolyte and electrodes limit its application seriously. Herein, we introduce an organosilicon compound, 1,3-Divinyltetramethyldisiloxane (DTMDS), as multifunctional electrolyte additive to enhance the performance of LiNi0.5Mn1.5O4/Li batteries. DTMDS contains two functional groups: siloxane groups (Si-O) and unsaturated carbon-carbon double bonds (CC). Siloxane groups can capture hydrogen fluoride (HF) in electrolyte, and the carbon-carbon double bonds can form thin and dense passivation layer on both cathode and anode surfaces by polymerization. As a result, the capacity retention of the batteries can retain more than 95% after 500 cycles. This work provides a valuable reference for the design of multifunctional additives and stabilizing the interfaces of high-voltage lithium metal batteries.

Reaction mechanism of halogenated rubber crosslinking using a novel environmentally friendly curing system

Iron (III) acetylacetonate (Fe (acac)) in the presence of triethanolamine (TEOA) was utilized as a novel crosslinking agent for halogenated diene rubber. Following the assumption that the mechanism of the crosslinking bases on the Heck-type reaction mechanism, which requires the presence of a halogen and an unsaturated carbon-carbon double bond, chloroprene rubber (CR) and brominated butyl rubber (BIIR) were utilized as rubber matrices. The results of FTIR spectra analysis confirm the proposed mechanism and indicate that a Heck-type reaction is feasible for performing a crosslinking of halogenated diene rubbers. The use of the Fe (acac)/TEOA curing system results in a significant torque increase during the vulcanization, which confirms the high activity of those compounds. The elimination of halogen from a rubber macromolecular structure or elimination of a basic environment of the crosslinking reaction results in a deactivation of the new curing system.

High activity Pd-Fe bimetallic catalysts for aqueous phase hydrogenations

Palladium-iron bimetallic catalysts were synthesized using carbon-coated silica supports that provided high hydrogenation activity relative to monometallic palladium under condensed-phase hydrothermal conditions. The catalysts were applied to the hydrogenation of carbonyl groups in acetone, 2-pentanone, and propionaldehyde. While Fe incorporation independent of Pd-to-Fe ratio gave enhanced activity, the catalysts having more Fe than Pd gave more than a three-fold increase in hydrogenation activity relative to the Pd only counterpart. The activity enhancement appeared to be related to the influence of Fe on the Pd as Fe under the condensed-phase reaction conditions was inert. The catalysts were also tested for hydrogenation of unsaturated carbon-carbon double bond and aromatic rings in which more moderate activity enhancement was observed. Through evaluating the influence of Pd-to-Fe ratio on catalyst properties and catalytic performance for the range of molecules, it is proposed that the turnover frequency enhancement can be attributed to the formation of Pdδ− via Pd-Fe interaction.

ω-3 fish oil fat emulsion preconditioning mitigates myocardial oxidative damage in rats through aldehydes stress

ω-3 fish oil fat emulsions contain a considerable quantity of unsaturated carbon-carbon double bonds, which undergo lipid peroxidation to yield low-dose aldehydes. These aldehydes may stimulate the production of antioxidant enzymes, thereby mitigating myocardial oxidative damage. This study aims to (1) verify the cardioprotective effect of ω-3 fish oil fat emulsion in vivo and in vitro, and (2) determine whether aldehyde stress is a protective mechanism. For modeling purposes, we pretreated rats with 2 ml/kg of a 10% ω-3 fish oil fat emulsion for 5 days in order to generate a sufficient aldehyde stress response to trigger the production of antioxidant enzymes, and we obtained similar response with H9C2 cells that were pretreated with a 0.5% ω-3 fish oil fat emulsion for 24 h. ω-3 fish oil fat emulsion pretreatment in vivo reduced the myocardial infarct size, decreased the incidence of arrhythmias, and promoted the recovery of cardiac function after myocardial ischemia/reperfusion injury. Once the expression of nuclear factor E2-related factor 2 (Nrf2) was silenced in H9C2 cells, aldehydes no longer produced enough antioxidant enzymes to reverse the oxidative damage caused by tert-butyl hydroperoxide (TBHP). Our results demonstrated that ω-3 fish oil fat emulsion enhanced the inhibition of oxidation and production of free radicals, and alleviated myocardial oxidative injury via activation of the Nrf2 signaling pathway.

Asymmetric Synthesis of α,β-Unsaturated δ-Lactones through Copper(I)-Catalyzed Direct Vinylogous Aldol Reaction

A simple methodology for the asymmetric synthesis of chiral α,β-unsaturated δ-lactones was achieved by copper(I)-catalyzed direct vinylogous aldol reaction (DVAR) of β,γ-unsaturated esters and various aldehydes, including aromatic aldehydes, heteroaromatic aldehydes, α,β-unsaturated aldehydes, and aliphatic aldehydes. For aromatic and heteroaromatic aldehydes, a one-pot reaction consisting of DVAR, isomerization of the unsaturated carbon-carbon double bond from ( E)-form to ( Z)-form, and subsequent intramolecular transesterification was required to get the lactones in moderate to high yields with high enantioselectivity. For α,β-unsaturated and aliphatic aldehydes, the DVAR proceeded directly to afford the lactones in moderate yields with high enantioselectivity. In the DVAR, various functional groups were well tolerated. Moreover, the methodology was nicely applicable to the aldehyde group distributed in natural products, derivatives of natural product, and derivatives of drug molecules (atomoxetine and naproxen). The mechanism studies revealed that α-addition was reversible and not favored, which accounted for the excellent regioselectivity in the DVAR. The copper(I)-dienolate species generated through deprotonation was proposed to form an equilibrium with an allylcopper(I) species, which reacted with aldehydes to afford the DVAR products through a catalytic asymmetric allylation of aldehydes. Finally, the robustness of the present reaction was demonstrated by a gram-scale reaction, and the utility of the present methodology was showcased by the formal asymmetric synthesis of ezetimibe and fostriecin.

Correlating surface activity with structural and environmental parameters for alkylamidosulfobetaine surfactants

Surface activities of 3-(N-alkylamidopropyl-N,N-dimethyl ammonium) alkanesulfonates [(U)n-DAS-m] and their dependence on the environmental and structural parameters were studied systemically. Environmental parameter–property relationship was investigated by changing salinity, pH, and temperature while using 3-(N-tetradecanoamidopropyl-N,N-dimethyl ammonium) propanesulfonates (14-DAS) as a model surfactant, whereas structure–property relationship was studied by changing the length of hydrophobic tail, the introduction of an unsaturated carbon-carbon double bond to the hydrophobic tail, and the distance between the positive and negative charges. Notably, the critical micelle concentration (cmc) of alkylamidosulfobetaine surfactants decreases monotonously with increasing NaCl content, following a linear function as lgcmc = A[NaCl] + B. The increase in temperature causes a slight decrease of γ cmc and a slight increase of cmc. The change in pH has no obvious effect on the solution properties of alkylamidosulfobetaine surfactants. The introduction of every two methylene units or an unsaturated carbon-carbon double bond in the hydrophobic tail results in the decrease of cmc by nearly one order of magnitude. The spacer length between the positive and negative charges has little effect on the surface activity of alkylamidosulfobetaines.

Thermal polymerization of lacquer sap and its effects on the properties of lacquer film

Abstract A series of thermal polymerized lacquers (TPL) were prepared from a dead lacquer at the temperature of 120–200 °C under nitrogen atmosphere. The thermal polymerization of lacquer sap was analyzed by GPC, UV–Vis, FT-IR and NMR methods. The results showed that the higher the temperature, the faster the polymerization of urushiol monomer in the lacquer sap. Different from the laccase-catalyzed oxidative polymerization in air which formed the biphenyl structures, the thermal polymerization mainly occurred in the unsaturated side chain of urushiol and could involve the pericyclic reaction between the unsaturated carbon-carbon double bonds and the reactions of the side chains with the phenolic hydroxyl groups and the carbons in the aromatic ring. Addition of the thermal polymerized lacquer into a raw lacquer sap with high activity of laccase at a suitable mixing ratio promoted its drying in air, and the higher the extent of thermal polymerization of lacquer sap, the shorter the drying time of lacquer film. In addition, due to the combination of the thermal polymerization and the laccase-catalyzed polymerization, the blend lacquer films showed higher degree of crosslinking, smoother surfaces, and more uniform and compact structure. This resulted in significant improvement in the pencil hardness and gloss of lacquer film and slight enhancement of its flexibility.

Prepolymerization of Lacquer Sap under Pure Oxygen Atmosphere and Its Effects on the Properties of Lacquer Film

A series of lacquer saps were prepared by prepolymerization under oxygen atmosphere. The prepolymerization process was investigated by GPC, UV-Vis, FT-IR, NMR, and microscope. The results showed that the polymerization of urushiol monomer was accelerated. The content of monomer in the lacquer sap swiftly decreased from 82.68% to 47.75% in 0.5 h. The mechanism of polymerization was complex and was involved in the coupling reaction of phenyl ring, the addition reaction of the unsaturated carbon-carbon double bond groups with urushiol hydroxyl groups, and other reactions that occurred on the side chains. In addition, the prepolymerization also improved significantly the drying property of lacquer film, especially at low relative humidity. At the same time, the sizes of the water drops in the lacquer saps significantly decreased with increasing the stirring time and the surface of lacquer film became smoother, which resulted in its excellent gloss (109–125). Due to the prepolymerization, the pencil hardness and the thermal stability of lacquer film were slightly improved as well.

A polyaromatic molecular tube that binds long hydrocarbons with high selectivity.

Long hydrocarbon chains are essential components of biomolecules used for structure and function in living organisms. The selective recognition and effective binding of hydrocarbons within synthetic host compounds are problematic owing to their conformational flexibility and the lack of specific binding sites. Here we report a molecular tube with polyaromatic frameworks prepared by the Zincke cross-coupling reaction. The tube has a well-defined cylindrical cavity with a diameter and length of ~1 nm encircled by multiple anthracene panels and thereby binds long hydrocarbons containing branched methyl groups and/or unsaturated carbon-carbon double bonds (for example, heptamethylnonane, nervonic acid ester and squalene) with high selectivity in aqueous solutions.

Upgrading of bio-oil molecular distillation fraction with solid acid catalyst

Molecular distillation technology has been adopted to obtain a bio-oil fraction rich in carboxylic acids and ketones. This unique bio-oil fraction was then upgraded with a La-promoted solid acid catalyst. Three washing pretreatments were used to prepare catalysts A, B, and C, with the intention of reducing the amounts of residual sulfuric acid. Model reactions were used to estimate their catalytic activities and the residual amounts of sulfuric acid. Catalyst B, with washing after calcination, displayed higher catalytic activity (80.83%) and lower residual amount of sulfuric acid (50 μmol/g). The catalysts were characterized by techniques such as BET, XRD, and SEM to explain the differences in their catalytic activities. The optimum catalyst B was used in the upgrading of the bio-oil molecular distillation fraction. After upgrading, the corrosivity of the bio-oil fraction declined and its storage stability was improved. The carboxylic acid content in the upgraded bio-oil fraction decreased from 18.39% to 2.70%, while the ester content increased from 0.72% to 31.17%. The conversion of corrosive carboxylic acids to neutral esters reduced the corrosivity of the bio-oil fraction. Moreover, the ketones with unsaturated carbon-carbon double bonds (such as 2-cyclopenten-1-one, 3-methyl-2-cyclopenten-1-one, etc.) were converted into saturated compounds, which improved the stability of the bio-oil fraction.

Controllable Synthesis of New Polymerizable Macrosurfactants via CCTP and RAFT Techniques and Investigation of Their Performance in Emulsion Polymerization

We reported herein the synthesis of poly(methacrylic acid)-b-poly(butyl acrylate) (PMAA-b-PBA) block copolymers (surfmers) and their performance as novel polymerizable macrosurfactants in emulsion polymerization. The surfmers bearing terminal unsaturated carbon-carbon double bonds were first successfully designed and sythesized via catalytic chain transfer polymerization (CCTP) and radical addition-fragmentation polymerization (RAFT) techniques. The structures of surfmers were characterized by Raman spectra, nuclear magnetic resonance ((1)H NMR), and gel permeation chromatography (GPC). The critical micelle concentration of surfmers was determined. Subsequently, the surfmers were used as emulsifier to prepare polyacrylate latexes (PA-surf). The influence of the surfmer concentration as well as PMAA and PBA chain segment ratios of surfmer on their performance in emulsion polymerization was discussed thoroughly. The particle size, amount of coagulum, and stability against electrolyte solutions of the latexes were evaluated. Also, the relations between monomer conversion in emulsion polymerization, polymerization rate, emulsion particle size, surface tension, and reaction time were investigated, which showed some interesting information for the probable mechanism underlying this emulsion polymerization system. Atomic force microscopy (AFM) and attenuated total reflection Fourier transform infrared spectra (ATR FT-IR) were performed to investigate the surface morphology and component distribution of the latex films. The results show high efficiency of these surfmers in emulsion polymerization, suggesting that the resultant PMAA-b-PBA block copolymers act not only as the emulsifier but also as the stabilizer of monomer droplets as well as the so-called comonomer.

Structure and Properties of Natural Rubber-Organoclay Nanocomposites Prepared by Grafting and Intercalating Method in Latex

The nanocomposites of natural rubber (NR) and organoclay with unsaturated carbon-carbon double bonds (C1/4C) on interlayer surfaces (USMMT) are prepared by the grafting and intercalating method in latex in the presence of butyl acrylate (BA) monomer. The conversion, grafting efficiency, and grafting percentage of BA onto NR and USMMT are determined. The structure and morphology of the nanocomposites are characterized by X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), transmitted electron microscopy (TEM), differential scanning calorimetry (DSC), dynamic mechanical analysis (DMA), and swelling experiments. The mechanical properties of the nanocomposites are measured. The results show that graft copolymerization of BA monomer onto NR molecular chains can take place with high conversion, grafting percentage, and grafting efficiency. At the same time, BA can intercalate into the interlayer galleries of USMMT and polymerize in situ together with C1/4C bonds on the interlayer surfaces. As a result, the interlayer spacing of organoclay is increased and the interfacial combination between the silicate layers and rubber is strengthened. The results of XRD and TEM demonstrate the formation of the nanocomposites of NR-M-USMMT. The glass transition temperatures of the nanocomposites are higher than that of the NR vulcanizate. The mechanical properties of the nanocomposites are remarkably improved compared with those of the NR and NR-USMMT vulcanizate.

ニッケル触媒により水と亜鉛末とから水素を生成する簡便法

Under nitrogen atmosphere an unsaturated carbon-carbon double bond was hydrogenated to give a saturated one with nickel catalyst system(NiBr2/Zn/H2O/EtOH). It was found that hydrogen gas was generated from water and zinc powder by using metallic nickel catalyst, which was prepared from anhydrous nickel bromide and zinc powder. Metallic nickel was an active species for the reaction and zinc powder was a reagent to produce hydrogen. A probable pathway was presented.

Degradation of hyaluronate by Streptococcus intermedius strain UNS 35.

Streptococcus intermedius strain UNS 35, a brain abscess isolate, produced extracellular hyaluronidase when grown in brain heart infusion broth. Chemical assays with this enzyme indicated that hyaluronate depolymerisation resulted in the formation of carbohydrate moieties with N-acetylglucosamine at the reducing terminal and containing an unsaturated carbon-carbon double bond. The nature of the products of this hyaluronidase were investigated further by high-field (400 MHz) proton (1H) NMR spectroscopy. Treatment of hyaluronate with the enzyme resulted in a series of new, sharp resonances in spectra (acetamido methyl group singlets located at 2.03 and 2.07 ppm, sugar ring proton multiplets in the 3.5-4.2 ppm chemical shift range, and doublets at 5.16 and 5.87 ppm) characteristic of low-M(r) oligosaccharide species, predominantly those containing glucuronosyl residues with delta 4,5-carbon-carbon double bonds. Comparison of spectra acquired from hyaluronidase-treated samples with that of an authentic sample of 4-deoxy-L-threo-hex-4-enopyranosyluronic-acid-N-acetylglucosamine (delta UA GlcNAc) indicated that this disaccharide was a major product arising from the actions of this enzyme. When used in minimal media, hyaluronate supported growth of S. intermedius, with lactate as the major metabolic end-product.

Smectic C phenylpyridines with an alkenyloxy chain

Abstract The known 5-n-alkoxy-2-[4-(n-alkoxy)phenyl]pyridines exhibit high smectic C transition temperatures as well as various highly ordered smectic mesophases. An unsaturated carbon-carbon double bond has now been introduced into the terminal alkoxy chain of these heterocyclic materials to produce the corresponding alkenyloxy substituted derivatives. The postion and nature (E/Z) of the double bond has been varied systematically and the effect on the liquid crystal transition temperatures determined. A number of homologous series of the most promising alkenyloxy substituted materials has been prepared and evaluated. The position and nature (E/Z) of the double bond changes the conformation of the alkenyloxy chain to a significant degree. This can lead to slightly higher smectic C transition temperatures for compounds with a trans-double bond (E) at an even number of carbon atoms from the molecular core. However, the highly ordered mesophase transition temperatures are increased to a greater degree leading to a reduction in the smectic C temperature range. Significantly lower transition temperatures (including the melting point) are observed for materials with a cis-double bond (Z) at an odd number of carbon atoms from the molecular core. Comparisons with the corresponding alkoxy substituted materials (i.e. without a double bond) are made. These new alkenyloxy materials can be used to increase the smectic C and nematic transition temperatures of chiral mixtures for electrooptical display devices based on ferroelectric effects.