The features of nitric acid ‘mercerization’ of cellulose

Transformation of native cellulose species into cellulose-II polymorph through the additive Knecht compound formed under the action of 68.5% nitric acid has been studied. Probable causes of peculiar temperature effects in the course of phase transformations taking place in cellulose of various origin, crystallite dispersity, or morphologic structure are discussed. The processes of hydrolytic destruction and esterification of starting materials during their mercerization by this non-traditional agent at 20 °C and 0 °C are quantitatively characterized. In the case of mercerization of wood microcrystalline cellulose at 20 °C a decrystallizing effect due to side reactions of partial nitration is noted.     

HPLC-spectrophotometric detection of trace heavy metals via ‘cascade’ separation and concentration

A cascade pre-concentration and separation system involving continuous solid-phase extraction and one-drop solvent concentration was developed to enable high-performance liquid chromatography (HPLC) determination of trace levels of Ni(II), Co(II), Cu(II), Se(IV) and Cr(VI) ions in aqueous solution via complexation with sodium diethyldithiocarbamate. The metal complexes were almost completely adsorbed on the solid phase (octadecylsilyl packed column). Ethyl acetate (eluent) containing the metal complexes was then placed in a centrifuge tube, to which a microvolume of dimethyl sulfoxide (DMSO) was added. Successful pre-concentration of the metal complexes into the DMSO phase was accomplished by removing the ethyl acetate using a compact evaporator in a water bath (40°C); 1000-fold concentration was achieved within 45 min. A portion of the residual DMSO phase was then subjected to HPLC analysis. The proposed method has high reproducibility and high sensitivity with detection limits (3σ) for Ni(II), Co(II), Cu(II), Se(IV) and Cr(VI) ions of 0.08, 0.11, 0.12, 0.44 and 0.20 µg/L, respectively. Relative standard deviations (RSDs) (n = 5) at Ni(II) 5.87 µg/L, Co(II) 5.89 µg/L, Cu(II) 6.35 µg/L, Se(IV) 7.90 µg/L and Cr(VI) 5.20 µg/L (1.0 × 10^?7 mol/L each) were 4.0%, 4.6%, 4.6%, 7.2% and 3.4%, respectively.     

The electro‐optical properties of ‘charged’ PDLCs

The application of high intensity electric fields to polymer dispersed liquid crystal (PDLC) films can induce changes in their electro‐optical properties and morphology. In particular, a quasilinear electro‐optical response to an external electric field can be achieved if an internal built‐in d.c. field is induced. In this work, we show how the liquid crystal/polymer weight ratio influences the electro‐optical response of ‘charged’ PDLCs, i.e. of PDLC films after the application of a high intensity electric field. We observed that a quasilinear electro‐optical response can be achieved in a well determined range of composition. Larger liquid crystal concentrations are unable to maintain the built‐in field, while PDLCs with lower liquid crystal loadings do not allow the onset of a built‐in d.c. field.     

The Emergence and Properties of Selectively Fluorinated ‘Janus’ Cyclohexanes

This account describes the evolution of a research programme that started by linking fluoromethylene (−CHF−) groups along aliphatic chains and then progressing to alicyclic rings with contiguous fluorine atoms. Different stereoisomers of aliphatic chains tend to adopt low polarity conformations. In order to force polar conformations, the programme began to address ring systems and in particular cyclohexanes, to restrain conformational freedom and co-aligned C−F bonds. The flagship molecule, all-cis-1,2,3,4,5,6-hexafluorocyclohexane 7 , emerged to be the most polar aliphatic compound recorded. The polarity arises because there are three co-aligned triaxial C−F bonds and the six fluorines occupy one face of the ring. Conversely the electropositive hydrogens occupy the other face. These have been termed Janus face cyclohexanes after the Roman god with two faces. The review outlines progress by our group and others in preparing derivatives of the parent cyclohexane 7 , in order to explore properties and potential applications of these Janus cyclohexanes.     

The Viscosity of Dilute Solution of a Novel Polymer ‘Dextran’ in Different Solvents

Abstract

The viscosity of dilute solution of a water soluble polysaccharide “Dextran” has been studied in 6(M) Urea, 2(M) Glycine and 50% Glucose solution in three different temperatures - 40°C, 45°C and 50°C. From the solution viscosity measurement, thermo viscosity parameters like Huggins' constant (k′_H). Kraemer's constant (k″_H) and the viscosity concentration coefficient (a₂) have been estimated from viscosity concentration plots. The value of these parameters have been characterized and compared with the theoretical value. The evaluation of these constants enable to know the fate of polymer molecules in the solution.     

Thermal investigation of ‘molten starch’

Detailed thermal analysis studies have shown that a ‘molten starch’ phase is obtained during controlled heating of starch. Before the ‘molten’ stage, depolymerisation of starch produces lower molecular weight compounds like dextrins, oligo, di- and monosaccharides, as well as other types of compounds. These compounds should have ideal properties for plasticizing starches because of the similarities of the molecules, helping lower phase changes in collaboration with molecular weight decrease. Interestingly, it was found previously that these materials only act as adhesives in a narrow temperature range around 523 K (250 °C) (Shuttleworth et al. J Mater Chem 19(45):8589–8593, 2009). Materials were investigated using thermal and mechanical analyses of single lap joints.     

The low concentration aggregation of sodium oleate–sodium linoleate aqueous mixtures

Sodium oleate (NaOL, C₁₈H₃₃O₂Na)–sodium linoleate (NaLin, C₁₈H₃₁O₂Na) mixtures were studied in the micellar and in the air/water interface states at 298.15 K. Three aggregation steps were found: a premicellar aggregation, the critical micelle concentration (CMC), and a structural change of micelles. Micelles, both at the CMC and at the structural change concentration, are richer in oleate than the overall mixture composition. Micelles are strongly non-ideal and the interaction is repulsive. The non-ideal behavior and the dependence of the micelle ionization degree with micelle composition are explained on the basis of the interaction of the π electrons of the surfactants’ chains with water at the hydrocarbon/water micellar interface. The air/solution adsorbed monolayer is also non-ideal, but the interaction is attractive and there is a preferential composition with a mole fraction of sodium oleate of about 0.7. The surface pseudophase behaves as if oleate were the solvent and linoleate a strongly soluble solute. This behavior and the dependence of the average area per adsorbed molecule were explained on the basis of the interaction of the double bonds with water. At the air/solution interface, the linoleate molecule area was similar to that of a heterogemini surfactant having a spacer with seven carbon atoms.     

The application of ‘Z’-shaped UV cells in open-tubular capillary column liquid chromatography

Summary Z-shaped UV cells for packed capillary columns cannot be used in open-tubular capillary column liquid chromatography (OT-LC) because of their relatively large volume. With post-column solvent make-up, a commercial Z-shaped cell (volume 100 nl) was used in our OT-LC system, resulting in 9-fold sensitivity increase against on-column UV detection and with little efficiency loss. A small volume (5 nl) Z-shaped cell allows the direct coupling of the cell to high efficiency columns. For dilute samples, 9-19-fold sensitivity enhancement could be obtained. However, column efficiency decreases with increasing signal level as a result of peak deformation.     

The effect of agitation speed,enzyme loading and substrate concentration on enzymatic hydrolysis of cellulose from brewer’s spent grain

Brewer’s spent grain components (cellulose, hemicellulose and lignin) were fractionated in a two-step chemical pretreatment process using dilute sulfuric acid and sodium hydroxide solutions. The cellulose pulp produced was hydrolyzed with a cellulolytic complex, Celluclast 1.5 L, at 45 °C to convert the cellulose into glucose. Several conditions were examined: agitation speed (100, 150 and 200 rpm), enzyme loading (5, 25 and 45 FPU/g substrate), and substrate concentration (2, 5 and 8% w/v), according to a 2³ full factorial design aiming to maximize the glucose yield. The obtained results were interpreted by analysis of variance and response surface methodology. The optimal conditions for enzymatic hydrolysis of brewer’s spent grain were identified as 100 rpm, 45 FPU/g and 2% w/v substrate. Under these conditions, a glucose yield of 93.1% and a cellulose conversion (into glucose and cellobiose) of 99.4% was achieved. The easiness of glucose release from BSG makes this substrate a raw material with great potential to be used in bioconversion processes.     

Synthesis and Crystal Structure of N—（1‘’‘’—Phenyl—2‘’‘’—hydroxyethyl）—2,3—naphthylenedicarboximide

IntroductionThe design and the synthesis of new chiral ox-azoline[1,2 ] and C2 symmetric bis( oxazoline) ligandsand the application of their metal complexes inasymmetric catalytic reactions have inspired manyscientists to great exertions in recent years[3— 8] .Our interest has been focussed on the studies ofenantioselective transition metal catalysis ofhetero-cyclic ligands[9— 11] . In the synthesis of our new de-signed ligands,what is crucial is to select a rigidcyclic backbone. Bis( oxazo…     

The estimation of ether’s enthalpies of formation

Taking hydrocarbon as gerneratrix, the differences of enthalpies of formation of ether and their corresponding generatrixes were compared and concluded and the equation to estimate ether’s enthalpy of formation, which was Δ_f H _e^°/(kJ/mol) = K(Δ_f H _m^ℴ − 90 + A) was obtained. The results can be elucidated with bond dissociation energies data, bond-enthalpy of formation method, induction effect and conjugative effect. The more essential account to explain the results can be got by using quantum chemistry theories, etc. Using replacement and comparison method, the way of estimation of organic compounds’ thermodynamic properties including enthalpy of formation can be obtained either. The article is published in the original.     

The Biochemistry of Life’s Energy

On December 10, 1997, the 101st anniversary of Alfred Nobels death, in Stockholms Concert Hall Swedish King Carl XVI Gustav awarded one half of the 1997 Nobel Prize in Chemistry (3.75 million kronor, about $500,000) to Professor Emeritus Paul Delos Boyer, age 79, of the University of California, Los Angeles and Dr. John Ernest Walker, age 56, of the Medical Research Council Laboratory of Molecular Biology, Cambridge, England for their elucidation of the enzymatic mechanism underlying the synthesis of adenosine triphosphate (ATP) and one half (3.75 million kronor, about $500,000) to Professor Emeritus Jens Christian Skou, age 79, of Århus University, Århus, Denmark for the first discovery of an ion-transporting enzyme, Na⁺, K⁺-ATPase.     

‘Intelligent’ alarm detector of gas leaks

Three types of tin oxide gas sensors have been developed and a gas-detecting apparatus using the developed sensors has been manufactured. This apparatus has the ability to identify the type of leaking gas out of isobutane, ethanol, hydrogen and carbon monoxide. It can also be used for accumulating data as the terminal unit of a microcomputer. When city gas or carbon monoxide gas is leaking, a pulse is output from the apparatus to an electromagnetic valve which cuts off the path of the gas. The use of the apparatus and microcomputer composes a countermeasure system against gas leak accidents.     

Consequences of the ‘jacketed’ effect on mesomorphic and orientational properties of ‘side-on fixed’ liquid crystalline polymers

Abstract

The mesomorphic properties have been studied as a function of the degree of polymerization for certain ‘side-on fixed’ polyacrylates. A peculiar evolution of the clearing temperature, T _IN, as well as of the glass transition temperatures, T _g, revealed that beyond a certain backbone length, T _IN and T _g decrease as the main chain length increases. The nematic ‘jacketed’ structure of these polymers induces a more or less high anisotropy of the polymer backbone conformation in the nematic phase and this can counterbalance the usual effect of an increase in the degree of polymerization on the thermodynamical properties of these systems. This evolution allows us to explain the unusual diamagnetic anisotropy anomaly observed as a function of temperature for this type of polymer.     

Elemental mercury vapour in air: the origins and validation of the ‘Dumarey equation’ describing the mass concentration at saturation

The Dumarey equation has been the dominant relationship used to calculate the mass concentration of saturated elemental mercury vapour in air for the calibration of mercury vapour measurement equipment for over 25 years. However, the origin of the equation, and the validation data supporting its accuracy have never been published. This paper addresses that deficiency, compares the Dumarey equation with other data sets to which it has been wrongly attributed in the past, and describes why it remains superior to the use of mercury vapour pressure data in combination with the ideal gas law, for the purposes of calibrating mercury vapour measurement equipment.