Phase transition thermodynamics of phenyl and biphenyl naphthalenes

This work is focussed on the thermodynamics of phase transition for some naphthalene derivatives: 1-phenylnaphthalene, 2-phenylnaphthalene, 2-(biphen-3-yl)naphthalene, and 2-(biphen-4-yl)naphthalene.The Knudsen mass-loss effusion technique was used to measure the vapour pressures of the following compounds: 2-phenylnaphthalene (cr), between T= (333.11 and 353.19) K; 2-(biphen-4-yl)naphthalene (cr), between T = (405.17 and 437.19) K; 2-(biphen-3-yl)naphthalene (l), betweenT = (381.08 and 413.17) K. From the temperature dependence of the vapour pressure, the standard, (p = 10⁵ Pa), molar enthalpies, entropies, and Gibbs free energies of sublimation for 2-phenylnaphthalene and 2-(biphen-4-yl)naphthalene were derived as well as the standard molar enthalpy, entropy, and Gibbs free energy of vaporization for 2-(biphen-3-yl)naphthalene at 298.15 K. The temperatures and the standard molar enthalpies of fusion were measured by differential scanning calorimetry and the standard molar entropies of fusion were derived. For 1-phenylnaphthalene the standard molar enthalpy of vaporization at 298.15 K was measured directly using the Calvet microcalorimetry drop method.The 1-phenylnaphthalene is liquid at room temperature, showing a remarkably low melting point when compared to the 2-phenylnaphthalene isomer and naphthalene. A regular decrease of volatility with the increase of a phenyl group in para position at the 2-naphthalene derivatives was observed. In 2-(biphen-3-yl)naphthalene, the meta substitution of the phenyl group results in a significantly higher volatility than in the respective para isomer.     

Uptake of Hydrocarbons in Aqueous Solution by Encapsulation in Acyclic Cucurbit[n]uril‐Type Molecular Containers

The ability of two water‐soluble acyclic cucurbit[n]uril (CB[n]) type containers, whose hydrophobic cavity is defined by a glycoluril tetramer backbone and terminal aromatic (benzene, naphthalene) sidewalls, to act as solubilizing agents for hydrocarbons in water is described. ¹H NMR spectroscopy studies and phase‐solubility diagrams establish that the naphthalene‐walled container performs as well as, or better than, CB[7] and CB[8] in promoting the uptake of poorly soluble hydrocarbons into aqueous solution through formation of host–hydrocarbon complexes. The naphthalene‐walled acyclic CB[n] container is able to extract large hydrocarbons from crude oil into aqueous solution.     

Two‐step crystal–crystal phase transformation of N‐salicylidene‐p‐aminobenzoic acid by gas–solid reaction with aqua–ammonia vapour

Crystal–crystal phase transformation by external stimuli has attracted significant attention for application in switchable materials, which can change their structures and properties. Herein, it is revealed that N‐salicylidene‐p‐aminobenzoic acid crystals undergo a two‐step crystal–crystal phase transformation through a gas–solid reaction with aqua–ammonia vapour. The photochromic behaviour of the crystals switched from nonphotochromic to photochromic and back to nonphotochromic via a phase transformation. The two‐step phase transformation and photochromic behaviour change were characterized and correlated by X‐ray crystal structure analysis, UV–Vis spectroscopy, differential scanning calorimetry and scanning electron microscopy. This article is the first report to capture the stepwise structural change in the gas–solid (acid–base) reaction of ammonia with benzoic acid derivatives.     

Stabilization of Bicontinuous Cubic Phase and Its Two-Sided Nature Produced by Use of Siloxane Tails and Introduction of Molecular Nonsymmetry

A recent intriguing finding that a helical network arrangement forms the bicontinuous cubic phase is attracting great attention for the possibility of new routes to asymmetric synthesis by achiral molecules. However, the design of the molecular structure for the cubic phase is still unrevealed. In this work, a nonsymmetric core molecule with larger naphthalene and smaller benzene moieties at each side of the central linkage and the same disiloxanyldecyloxy terminal at both terminals is shown to be the first example of molecule forming both single-layered and double-layered core assembly modes in the Ia3d phase as a single molecule system. The molecule forms the former mode at high temperatures as a thermodynamically stable phase, similarly to the symmetric naphthalene core system, whereas, on cooling below a temperature (∼350 K), a metastable Ia3d phase forms a double-layered core state down to room temperature, which is common to the benzene core system. As another effect of the nonsymmetric core, the cubic phase is maintained at room temperature for more than 100 days with slight distortion. Infrared spectral studies and quantum chemical calculations suggested the easy transformation between the two core assembly modes. The core nonsymmetry can be a versatile fine-tuning of the core assembly mode and phase stability for the cubic phase molecules.     

Monitoring of carcinogenic PAHs in air under mild–warm ambient temperatures: relative importance of vapour- and particulate-phase analyses in assessing exposure and risk

Atmospheric polycyclic aromatic hydrocarbons (PAHs) are often determined by collecting only the particulate phase. The aim of this study was to ascertain in the field to what extent not collecting the vapour phase may affect the exposure assessment and the risk assessment for carcinogenic PAHs, under ambient temperatures typical of Southern Europe. PM₁₀ 24-h samples were collected in Rome every two months throughout one year on a filter backed by two polyurethane foam sections. Daily mean temperatures during sampling reached 31°C, with hourly maximum values up to 36°C. While four-ring PAHs were found in the vapour phase to a large extent, the calculated annual means of five-ring PAHs, including benzo[a]pyrene, were not affected significantly by the amounts collected as vapour phase. By using the “toxicity equivalence factor” approach, the carcinogenic risk overall attributable to particle-bound PAHs accounted for at least 97% of the risk attributable to total (particulate + vapour phase) PAHs.     

The role of the interface in a Ti‐based metallic glass matrix composite with in situ dendrite reinforcement

Many in situ metallic glass matrix (MGM) composites have been developed as promising engineering materials having distinguished properties because of sharing virtues of high strength of metallic glasses and large plasticity of crystal phase, for example, Ti₄₇Zr₁₉Be₁₅V₁₂Cu₇ MGM composites (the yield strength: 1600 MPa, the fracture strength: 3024 MPa and the total strain 32.6%). Although the toughening mechanisms in these materials have been investigated, the role of the interface bridging the ductile dendrite and the glass phase is still unclear. To this aim, specimens of the as‐received and after compression of this Ti‐based MGM composite were investigated to by using the transmission electron microscopy and the high‐resolution transmission electron microscopy. The results of the microstructure investigation indicated that the interface in the composite consists of a nanosized transform layer with an approximate width of 4 nm. During plastic deformation, the interface either suppresses plastic deformation caused by dislocations on the dendrite side or initiates nucleation of multiple shear bands throughout nanocrystallization on the glass phase side nearby the interface, which is favorable for the plastic deformation of the material. Copyright © 2014 John Wiley & Sons, Ltd.     

Preparation and Evaluation of 3,5-Dinitrobenzoyl-Bonded Silica Gel Stationary Phase for HPLC

Column packing materials are always a key factor influencing the development of high-performance liquid chromatography (HPLC). In this paper, a new preparation method of 3,5-dinitrobenzoyl-bonded silica gel stationary phase (DNB) for HPLC was developed by using N-(β-aminoethyl)-γ-aminopropyl-methyldimethoxy silane as coupling reagent. Its structure was characterized by elemental analysis, diffuse reflectance infrared Fourier transform spectroscopy, and thermal analysis. The surface concentration of 3,5-dinitrobenzoyl ligand is 2.082 μmol m⁻², according to the carbon content of elemental analysis. The chromatographic performance of new packing was evaluated by using different solute probes, such as alkylbenzenes, polycyclic hydrocarbons (PAHs), phenols, naphthalene derivatives, nitrophenol positional isomers, and sulfonamides. The results show that DNB was of the reversed-phase packing kind with weak hydrophobicity and versatile chromatographic property compared with octadecyl silane. The charge transfer between the dinitrobenzoyl ligand and the analytes plays a significant role in the separation of phenols and naphthalene derivatives. In addition, electrostatic, hydrogen-bonding, and dipole-dipole interactions are responsible for the above separations, which improve the selectivity of DNB for solutes. An advantage of DNB is that it is suitable for the separation of the basic compounds containing nitrogen atoms without a capped process because the spacer containing nitrogen atoms can shield the residual silanols from DNB. Translated from Chinese Journal of Chromatography, 2005, 23(3) (in Chinese)     

Barrier and mechanical properties of modified starches

The study addressed starch-based coatings on paper and fabrics. Coated materials and free starch films containing different amounts of a well-established plasticizer (glycerol) or potential plasticizer (mainly polyols) were tested with respect to water vapour permeance (WVPe), water vapour permeability (WVP), glass transition temperature (T_g), and mechanical strength (tensile tests). Both normal and high- amylose potato starch were used. These starches were modified by (a) oxidation, (b) oxidation and hydroxypropylation or (c) oxidation and hydrophobically modified by reaction with octenyl- or alkenyl-substituted succinic acid anhydride. Free films of hydroxypropylated high-amylose potato starch showed a lower WVP than did the corresponding starches based on regular potato starch. The WVP of the hydrophobically modified regular potato starches was substantially higher than that of films of the corresponding hydroxypropylated starches. The expected hydrophobic effect of the succinic acid anhydrides in terms of a reduced WVP could not be observed. When glycerol was used as a plasticizer, about 30 parts (by wt.) per hundred parts of starch were needed in order to reduce the T_g and to cause observable changes in the mechanical properties of the free films.     

Solid-liquid equilibrium using the SAFT-VR equation of state: Solubility of naphthalene and acetic acid in binary mixtures and calculation of phase diagrams

A solid-liquid equilibrium (SLE) thermodynamic model based on the SAFT-VR equation of state (EOS) is presented. The model allows for the calculation of solid-liquid phase equilibria in binary mixtures at atmospheric pressure. The fluid (liquid) phase is treated with the SAFT-VR approach, where molecules are modelled as associating chains of tangentially bonded spherical segments interacting via square-well potentials of variable range. The equilibrium between the liquid and solid phase is treated following a standard thermodynamic method that requires the experimental temperature and enthalpy of fusion of the solute. The model is used to calculate the solubilities of naphthalene and acetic acid in common associating and non-associating organic solvents and to determine the solid-liquid phase behaviour of binary mixtures with simple eutectics. The SAFT-VR pure component model parameters are determined by comparison to experimental vapour pressure and saturated liquid density data with the choice of association models according to the nature of the molecule; in addition, an unlike adjustable parameter (k_ij) is used to model the solutions. The solubility data of naphthalene and acetic acid in both associating and non-associating solvents are reproduced essentially within the accuracy of the experimental measurements. The phase boundaries and the position of the eutectic points in the binary mixtures considered are, in most cases, reproduced with the accuracy commensurate with the industrial applications. Overall, the results presented show that the SAFT-VR EOS can be used with confidence for the prediction of the SLE of binary systems at atmospheric pressure.     

Direct observation of a 220 cm structure in the lowest π–π* absorption band in the vapour phase of trans-azobenzene

In this work we present the first direct observation of a 220 cm⁻¹ progression in the absorption spectrum of trans-azobenzene in the vapour phase. The mode at 220 cm⁻¹ is essential to explain both the electronic absorption spectrum and the Raman excitation profiles of the most intense Raman bands of trans-azobenzene in the 1000–1600 cm⁻¹ shift range. Our data in the vapour phase assure that this frequency pertains to an internal molecular mode.     

One donor–two acceptor (D–A1)‐(D–A2) random terpolymers containing perylene diimide,naphthalene diimide,and carbazole units

A series of one donor–two acceptor (D–A₁)‐(D–A₂) random terpolymers containing a 2,7‐carbazole donor and varying compositions of perylene diimide (PDI) and naphthalene diimide (NDI) acceptors was synthesized via Suzuki coupling polymerization. The optical properties of the terpolymers are weighted sums of the constituent parent copolymers and all show strong absorption over the 400 to 700 nm range with optical bandgaps ranging from 1.77 to 1.87 eV, depending on acceptor composition. The copolymers were tested as acceptor materials in bulk heterojunction all‐polymer solar cells using poly[(4,8‐bis‐(2‐ethylhexyloxy)‐benzo[1,2‐b;4,5‐b′]dithiophene)‐2,6‐diyl‐alt‐(4‐(2‐ethylhexanoyl)‐thieno[3,4‐b]thiophene)‐2,6‐diyl] (PBDTTT‐C) as the donor material. In contrast to the optoelectronic properties, the measured device parameters are not composition dependent, and rather depend solely on the presence of the NDI unit, where the devices containing any amount of NDI perform half as well as those using the parent polymer containing only carbazole and PDI. Overall this is the first example of a one donor–two acceptor random terpolymer system containing perylene diimide (PDI) and naphthalene diimide (NDI) acceptor units, and demonstrates a facile method of tuning polymer optoelectronic properties while minimizing the need for complicated synthetic and purification steps. © 2014 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2014 , 52, 3337–3345     

Thermodynamics and vacuum distillation studies of liquid Al–Ga and In–Sn alloys

Activities of components in liquid Al–Ga and In–Sn alloys, the separation coefficients and vapour–liquid phase equilibrium in vacuum distillation were predicted using the molecular interaction volume model as a function of the activity coefficients. The results indicated that both Al and In are preferentially volatilised into vapour phase while Ga and Sn remain in residue. Similarly, we found that both the mass fraction and the content of Al and In in vapour phase increase as distillation temperature increases such that when the content of Al is 0.005985 wt% and In is 0.004141 wt% in vapour phase, respectively, in liquid phase, it was 70 wt% at T = 1073 K for both. The calculated values of activity and activity coefficients at various temperatures are presented. Comparison of the predicted values with experimental data indicates good agreement, thus verifying from statistical thermodynamics viewpoint that the model is stable and reliable.     

Use of Chemically Bonded β‐Cyclodextrin Silica Stationary Phase for Liquid Chromatographic Separation of Structural Isomers

The retention behavior of five disubstituted benzene derivatives and two naphthalene derivatives is examined by using a chemically bonded β‐cyclodextrin silica stationary phase with the moiety containing the s‐triazine. The chromatographic results of five disubstituted benzene derivatives and two naphthalene derivatives show that effective separation is achieved on this stationary phase by high‐performance liquid chromatography. The results of the present investigation indicate that the formation of inclusion complexes plays a dominant role in the separation mechanism. However, the selectivity can be significantly enhanced by the n‐n interactions between the s‐triazine ring of the chemically bonded β‐cyclodextrin silica stationary phase and the aromatic ring of solutes. For example, the effective separation of the o‐, m‐, and p‐toluidine isomers on this stationary phase with the moiety containing the s‐triazine ring was better than on that of some β‐cyclodextrin bonded stationary phases without the moiety containing s‐triazine ring.     

Ferroelectrically Switching Helical Columnar Assembly Comprising Cisoid Conformers of a 1,2,3‐Triazole‐based Liquid Crystal

The 1,2,3‐triazole molecule, which is a product of click chemistry, possesses a high dipole moment and can be a useful polar motif for ferroelectric columnar liquid crystal (LC) materials—though it has not been used to date. Herein, we report the helical assembly and ferroelectric switching properties of a columnar liquid crystal comprising a naphthalene core and 1,2,3‐triazolyl linkages. The molecule assembles into a double‐stranded helical columnar LC structure (Col_hel). The X‐ray simulations of cisoid and transoid columnar models suggest that the helical assembly comprises cisoid conformers with a non‐zero dipole moment. The helical columns in the Col_hel phase are aligned homeotropically under an electric field. The ferroelectric switching of the axial polarization can be observed in the temperature range of 105–115 °C in the Col_hel phase, wherein the triazolyl hydrogen bonding along the column axis is weakened. The ferroelectric switching event is attributed to the rotation of the polar triazolyl units in response to the electric field.     

Determination of total mercury in environmental and biological samples using k0-INAA, RNAA and CVAAS/AFS techniques: Advantages and disadvantages

The accuracy and precision of the results obtained for total mercury in various environmental and biological samples and certified reference materials (CRMs) by various analytical methods, including k ₀-instrumental neutron activation analysis (k ₀-INAA), radiochemical neutron activation analysis (RNAA) and cold vapour atomic absorption (and atomic fluorescence) spectrometry (CVAAS/AFS) used in routine analysis in our laboratory, were investigated. Three natural matrix reference materials (RMs) from the International Atomic Energy Agency (IAEA), five CRMs from the Institute for Reference Materials and Measurements (IRMM), six CRMs from the National Institute of Standards and Technology (NIST) and one from the Jožef Stefan Institute (IJS) were analyzed. The results obtained show good agreement between certified or assigned values, and between the methods used, except for some data obtained by k ₀-INAA in biological samples. This can be explained by losses during irradiation in semi-open systems (irradiation in plastic ampoules) and/or spectral interferences. This revised version was published online in August 2006 with corrections to the Cover Date.     

Combination of analytical and microbiological techniques to study the antimicrobial activity of a new active food packaging containing cinnamon or oregano against E. coli and S. aureus

The aim of this work is the optimization and application of a group of analytical and microbiological techniques in the study of the activity of essential oils (EOs) incorporated in a new antimicrobial packaging material and the research in depth of the interaction between the microbial cells and the individual compounds present in the active material. For this purpose the antimicrobial activity of the active packaging containing cinnamon or oregano was evaluated against E. coli and S. aureus. The vapour phase activity and the direct contact between the antimicrobial agents themselves, or once incorporated in the packaging material, and the microbial cells have been studied. The direct contact was studied using a broth dilution method. The vapour phase was evaluated by using a new method which involves the use of a filter disk containing the EOs. Furthermore, the kill time assay was used to determine the exposure time for the maximum efficiency in packaging, and transmission electron microscopy was used to investigate the antimicrobial activity and the possible mechanism of action against E. coli and S. aureus. Finally, the compounds absorbed by cells were identified. The results showed that the techniques used provide relevant information about the antibacterial activity of cinnamon and oregano in direct contact as well as in the vapour phase. The antimicrobial packaging showed a fast efficiency which supports its likely application as a food packaging material. Bacteria treated with EOs exhibit a wide range of significant abnormalities; these include formation of blebs, coagulation of cytoplasmatic constituents, collapse of the cell structure and lack of cytoplasmatic material. Some of these observations are correlated to the ability of some of these substances to disrupt envelop structure, especially the inner membrane. After an extraction from dead cells, cinnamaldehyde was detected by GC-MS in E. coli exposed to the active packaging containing cinnamon.     

Fluorophore-labeled Polyamidoamine (PAMAM) Dendritic Architectures: Synthesis and Fluorescence Sensing Properties

Novel polyamidoamine (PAMAM) dendrimers (G=0.5–2.5) with a naphthalene core unit have been prepared. They were found to display acid as well as metal ion sensitive fluorescence signal amplification, making them of potential use as chemosensing materials. PAMAM dendritic wedges as well as naphthalene-centered PAMAM dendrimers were characterized by FT-IR, ¹H and ¹³C NMR spectroscopic methods and elemental analysis.     

Ni-intAlx催化剂的化学合成及萘选择加氢性能

非（类）金属掺杂金属形成金属间隙或金属间化合物是一种设计高效、高选择性催化剂的重要手段.我们以萘基锂为强还原剂,NiCl₂与AlCl₃为原料,在室温下化学合成了Ni-^intAl_x纳米催化剂,并采用pXRD、N₂物理吸附、XPS、TEM、H₂-TPR、H₂-TPD等手段对催化剂进行表征.以萘选择加氢为探针反应,结果显示Ni-^intAl_x催化剂对萘选择加氢制四氢萘具有高活性及单一选择性.其中Ni-^intAl₁催化剂具有比Ni样品更纯的FCC晶型,比Ni-^intAl_1/3更适宜的铝掺杂量,及比Ni-^intAl₃更适宜的活性组分含量.镍铝之间的电子效应在一定程度上可调变中间产物四氢萘的吸附性能,避免过度加氢,在优化条件下萘转化率和四氢萘选择性分别达97%和98%,铝可用作第二金属掺杂以提高金属位点的活性和对中间产物的选择性.     

Synthesis of a New Modification of Lithium Chloride Confirming Theoretical Predictions

In accordance with prior calculations, the new polymorph β‐LiCl (wurtzite structure type) has been synthesised, by the low‐temperature atomic‐beam‐deposition (LT–ABD) technique, in a mixture with α‐LiCl (rock salt structure type) by depositing LiCl vapour (2 to 5.3 × 10^–4 mbar) onto a cooled substrate (–30 to –60 °C). The maximum β‐LiCl fraction of 53 % was obtained using a sapphire (0001) substrate at –50 °C and 3.7 × 10^–4 mbar LiCl vapour pressure. The proportion of the new polymorph contained in the bulk sample decreases as temperature or vapour pressure deviate from these values, until finally the rock salt type LiCl is found exclusively. When the samples are warmed up to room temperature, β‐LiCl irreversibly transforms to α‐LiCl. The X‐ray diffraction pattern of the two phase LiCl sample measured at –50 °C has been indexed and refined based on a hexagonal unit cell for β‐LiCl with the lattice constants a = 3.852(1) Å and c = 6.118(1) Å and a cubic unit cell for α‐LiCl with the lattice constant a = 5.0630(8) Å. By Rietveld refinement the wurtzite type ofstructure (P6₃mc, No. 186) was suggested for the new hexagonal modification of LiCl with the Li–Cl distances (2.32 and 2.34 Å) being 8 % smaller than those of α‐LiCl. Moreover, the cell volume decreases as much as 16 % during the transition from β‐LiCl to α‐LiCl. Both the shifts in bond lengths and volume correspond well with the situation encountered for LiBr and LiI. Besides the variation of LiCl vapour pressure and substrate temperature, also different substrate materials were employed for testing their influence on formation of the β‐LiCl polymorph.     

Comparative structural analysis of 2,7‐diethoxy‐1,8‐bis(4‐phenoxybenzoyl)naphthalene and its homologues: orientation of the 4‐phenoxybenzoyl groups at the 1‐ and 8‐positions of the naphthalene ring

The title molecule, C₄₀H₃₂O₆, possesses crystallographically imposed twofold symmetry, with the central two C atoms of the naphthalene unit sited on the rotation axis. The two 4‐phenoxybenzoyl groups in the molecule are twisted away from the attached naphthalene unit, with a torsion angle of 66.76 (15)° between the naphthalene unit and the carbonyl group (C—C—C=O), and are oriented in mutually opposing directions (anti orientation). There is an apparent difference in the conformations of the 4‐phenoxybenzoyl groups at the 1‐ and 8‐positions of the naphthalene ring between the title molecule and its methoxy‐bearing homologue [Hijikata et al. (2010). Acta Cryst. E 66 , o2902–o2903]. Whilst the 4‐phenoxybenzoyl groups in 2,7‐diisopropoxy‐1,8‐bis(4‐phenoxybenzoyl)naphthalene [Yoshiwaka et al. (2013). Acta Cryst. E 69 , o242] are situated in the same anti orientation as the title molecule, those of 2,7‐dimethoxy‐1,8‐bis(4‐phenoxybenzoyl)naphthalene are oriented in the same direction with respect to the naphthalene ring system, i.e. in a syn orientation.