2,3,4,6‐Tetra‐O‐acetyl‐α‐d‐glucopyranosyl azide

The Cu^I‐catalysed 1,3‐dipolar cycloaddition of an azide and a terminal alkyne is becoming an increasingly popular tool for synthetic chemists. This is the most representative of the so‐called `click reactions' and it is used to generate 1,4‐disubstituted triazoles in high yield. During studies on such cycloaddition reactions, a reduced reactivity of an α‐glucosyl azide with respect to the corresponding β‐anomer was observed. With the aim of understanding this phenomenon, the structure of the title compound, C₁₄H₁₉N₃O₉, has been determined at 140 K. The glucopyranosyl ring appears in a regular ⁴C₁ chair conformation with all the substituents in equatorial positions, except for the anomeric azide group, which adopts an axial orientation. The observed bond lengths are consistent with a strong anomeric effect, which is reflected in a change in dipolar character and hence reduced reactivity of the α‐glucosyl azide.     

Hydroxyl‐ and amine‐terminated hyperbranched polyurethanes using AB2‐type azide monomers: Synthesis,characterization, fluorescence,and charge‐transfer complexation studies

Novel AB₂‐type azide monomers such as 3,5‐bis(4‐methylolphenoxy)carbonyl azide (monomer 1) , 3,5‐bis(methylol)phenyl carbonyl azide (monomer 2) , 4‐(methylol phenoxy) isopthaloyl azide (monomer 3) , and 5‐(methylol) isopthaloyl azide (monomer 4) were synthesized. Melt and solution polymerization of these monomers yielded hydroxyl‐ and amine‐terminated hyperbranched polyurethanes with and without flexible ether groups. The structures of theses polymers were established using FT‐IR and NMR spectroscopy. The molecular weights (M_w) of the polymers were found to vary from 3.2 × 10³ to 5.5 × 10⁴ g/mol depending on the experimental conditions used. The thermal properties of the polymers were evaluated using TGA and DSC: the polymer obtained from monomer ( 1 ) exhibited lowest T_g and highest thermal stability and the polymer obtained from monomer ( 2 ) registered the highest T_g and lowest thermal stability. All the polymers displayed fluorescence maxima in the 425–525 nm range with relatively narrow peak widths indicating that they had pure and intense fluorescence. Also, the polymers formed charge transfer (CT) complexes with electron acceptor molecules such as 7,7,8,8‐tetracyano‐quino‐dimethane (TCNQ) and 1,1,2,2‐tetracyanoethane (TCNE) as evidenced by UV‐visible spectra. © 2009 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 47: 3337–3351, 2009     

Theoretical prediction of the structural,elastic, electronic,optical and thermal properties of the cubic perovskites CsXF3 (X = Ca,Sr and Hg) under pressure effect

Some physical properties of the cubic perovskites CsXF₃ (X = Ca, Sr and Hg) have been investigated using pseudopotential plane-wave method based on the density functional theory. The calculated lattice parameters within GGA and LDA agree reasonably with the available experimental data. The elastic constants and their pressure derivatives are predicted using the static finite strain technique. We derived the bulk and shear moduli, Young's modulus, Poisson's ratio and Lamé’s constants for ideal polycrystalline aggregates. The analysis of B/G ratio indicates that CsXF₃ (X = Ca, Sr and Hg) are ductile materials. The thermal effect on the volume, bulk modulus, heat capacity and Debye temperature was predicted.     

Structural,elastic, electronic and thermal properties of the cubic perovskite-type BaSnO3

First-principles calculations are performed to investigate the structural, elastic, electronic and thermal properties of the cubic perovskite-type BaSnO₃. The ground-state properties are in agreement with experimental data. The independent elastic constants, C₁₁, C₁₂ and C₄₄, are calculated from direct computation of stresses generated by small strains. A linear pressure dependence of the elastic stiffnesses is found. From the theoretical elastic constants, we have computed the elastic wave velocities along [100], [110] and [111] directions. The shear modulus, Young's modulus, Poisson's ratio, Lamé’s coefficients, average sound velocity and Debye temperature are estimated in the framework of the Voigt-Reuss-Hill approximation for ideal polycrystalline BaSnO₃ aggregate. Using the sX-LDA for the exchange-correlation potential, the calculated indirect fundamental band gap value is in very good agreement with the measured one. The analysis of the site-projected l-decomposed density of states, charge transfer and charge density shows that the bonding is of ionic nature. Through the quasi-harmonic Debye model, in which the phononic effects are considered, the temperature effect on the lattice constant, bulk modulus, thermal expansion coefficient, heat capacity and Debye temperature is calculated.     

μ1,3‐Azido‐di­azidotetrakis(1,10‐phenanthroline)dicopper(II) azide tetra­hydrate

In the title compound, [Cu₂(μ‐_1,3‐N₃)(N₃)₂(phen)₄](N₃)·4H₂O (phen is 1,10‐phenanthroline, C₁₂H₈N₂), each of the two Cu atoms is surrounded by two N atoms of two azide anions and by four N atoms of two 1,10‐phenanthroline ligands [Cu—N distances are 1.964 (3), 2.009 (3), 2.018 (3), 2.054 (3), 2.306 (3) and 2.759 (4) Å], forming an elongated CuN₆ octahedron. An ideally linear μ_1,3‐azide anion bridges two Cu atoms to form a dimeric structure with the central N atom located on a centre of inversion. Moreover, the adjacent dimeric units are connected by hydrogen‐bond interactions to produce one‐dimensional chains. A two‐dimensional supramolecular array is formed by π–π interactions between the aromatic rings of 1,10‐phenanthroline ligands of adjacent dimeric units.     

Structural, electronic and elastic properties of MAX phases M2GaN (M = Ti, V and Cr)

Based on first-principles total energy calculations, we have investigated the systematic trends for structural, electronic and elastic properties of the MAX phases M₂GaN depending on the type of M transition metal (M are Ti, V and Cr). The optimized zero pressure geometrical parameters: the two unit cell lengths (a, c), the internal coordinate z and the bulk modulus are calculated. The results for the lattice constants are in agreement with the available experimental data. The band structures show that all studied materials are electrical conductors. The analysis of the site-projected l-decomposed density of states shows that bonding is due to M d-N p and M d-Ga p hybridizations. The elastic constants are calculated using the static finite strain technique. The shear modulus C₄₄, which is directly related to the hardness, reaches its maximum when the valence electron concentration is in the range 10.5–11.0. The isotropic elastic moduli, namely, bulk modulus (B), shear modulus (G), Young's modulus (E) and Poisson's ratio (σ) are calculated in framework of the Voigt–Reuss–Hill approximation for ideal polycrystalline M₂GaN aggregates. We estimated the Debye temperature of M₂GaN from the average sound velocity. This is the first quantitative theoretical prediction of the electronic structures, and elastic constants and related properties for Ti₂GaN, V₂GaN and Cr₂GaN compounds that require experimental confirmation.     

High-throughput first-principle calculations of the structural,mechanical, and electronic properties of cubic XTiO3 (X = Ca,Sr, Ba,Pb) ceramics under high pressure

High-throughput first-principle calculations are implemented to study the structural, mechanical, and electronic properties of cubic XTiO₃ (X = Ca, Sr, Ba, Pb) ceramics under high pressure. The effects of applied pressure on physical parameters, such as elastic constants, bulk modulus, Young's modulus, shear modulus, ductile-brittle transition, elastic anisotropy, Poisson's ratio, and band gap, are investigated. Results indicate that high pressure improves the resistance to bulk, elastic, and shear deformation for XTiO₃ ceramics. Pugh's ratios B/G reveal that CaTiO₃ and PbTiO₃ ceramics are ductile, but SrTiO₃ and BaTiO₃ ceramics are brittle under the ground state. The brittle-to-ductile transition pressures are 24.26 GPa for SrTiO₃ and 43.23 GPa for BaTiO₃. Under high pressure, the strong anisotropy promotes the cross-slip process of screw dislocations, and then enhances the plasticity of XTiO₃ ceramics. Meanwhile, XTiO₃ (X = Ca, Sr, Ba) is intrinsically an indirect-gap ceramic, but PbTiO₃ is a direct-gap ceramic. High pressure increases the band gap of XTiO₃ (X = Ca, Sr, Ba) ceramic, but decreases that of PbTiO₃ ceramic. This work is helpful for designing and applying XTiO₃ ceramics under high pressure.     

Synthesis of azide end‐functionalized isotactic polypropylene building block and renewed modular synthesis of diblock copolymers of isotactic polypropylene and poly(ε‐caprolactone)

This article details a synthesis of azide end‐functionalized isotactic polypropylene (i‐PP), a unique polymeric building block that can engage in Huisgen's 1,3‐dipolar cycloaddition of azide and alkyne (click reaction) to construct well‐defined i‐PP‐based polymer architecture. Controlled, consecutive chain transfer reaction to 1,2‐bis(4‐vinylphenyl)ethane and hydrogen in metallocene‐mediated propylene polymerization catalyzed by rac‐Me₂Si(2‐Me‐4‐Ph‐Ind)₂ZrCl₂/MAO resulted in styryl‐terminated i‐PP (i‐PP‐t‐St) of controlled molecular weight. Following a regioselective hydrochlorination reaction, the terminal styryl groups were quantatively transformed to 1‐chloroethylbenzene groups, which was further reacted with NaN₃ to give i‐PP terminated with an azide group (i‐PP‐t‐N₃). Structural monitoring of the polymers through the whole transformation process using ¹H NMR and FTIR as well as GPC and DSC reveals a clean and clear formation of i‐PP‐t‐N₃ (M_n in between 10,000 and 40,000 g/mol). This clickable i‐PP building block was applied to a renewed, modular synthesis of amphiphilic i‐PP‐b‐PCL (poly(ε‐caprolactone)) diblock copolymers. Composition‐diversified, structure‐well defined diblock copolymers were obtained in high yields, confirming both the high end group selectivity as well as high reactivity of azide the clickable moiety in the i‐PP building block and the effectiveness of azide‐alkyne click reaction in constructing new i‐PP architecture. © 2011 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2011     

Boron Phosphorus Nitride at Extremes: PN6 Octahedra in the High‐Pressure Polymorph β‐BP3N6

The high‐pressure behavior of non‐metal nitrides is of special interest for inorganic and theoretical chemistry as well as materials science, as these compounds feature intriguing elastic properties. The double nitride α‐BP₃N₆ was investigated by in situ single‐crystal X‐ray diffraction (XRD) upon cold compression to a maximum pressure of about 42 GPa, and its isothermal bulk modulus at ambient conditions was determined to be 146(6) GPa. At maximum pressure the sample was laser‐heated, which resulted in the formation of an unprecedented high‐pressure polymorph, β‐BP₃N₆. Its structure was elucidated by single‐crystal XRD, and can be described as a decoration of a distorted hexagonal close packing of N with B in tetrahedral and P in octahedral voids. Hence, β‐BP₃N₆ is the first nitride to contain PN₆ octahedra, representing the much sought‐after proof of principle for sixfold N‐coordinated P that has been predicted for numerous high‐pressure phases of nitrides.     

First principles prediction of the elastic,electronic, and optical properties of Sb2S3 and Sb2Se3 compounds

We have performed a first principles study of structural, mechanical, electronic, and optical properties of orthorhombic Sb₂S₃ and Sb₂Se₃ compounds using the density functional theory within the local density approximation. The lattice parameters, bulk modulus, and its pressure derivatives of these compounds have been obtained. The second-order elastic constants have been calculated, and the other related quantities such as the Young's modulus, shear modulus, Poisson's ratio, anisotropy factor, sound velocities, Debye temperature, and hardness have also been estimated in the present work. The linear photon-energy dependent dielectric functions and some optical properties such as the energy-loss function, the effective number of valence electrons and the effective optical dielectric constant are calculated. Our structural estimation and some other results are in agreement with the available experimental and theoretical data.     

An azide‐bridged copper(II) complex: poly[piperazine‐1,4‐dium [tetra‐μ3‐azido‐κ12N1:N1:N1‐hexa‐μ2‐azido‐κ12N1:N1‐di‐μ2‐azido‐κ4N1:N3‐pentacopper(II)] tetrahydrate]

A new Cu^II–azide complex, {(C₄H₁₂N₂)[Cu₅(N₃)₁₂]·4H₂O}_n, has been synthesized by the reaction of piperazine, Cu(OAc)₂·2H₂O (OAc is acetate) and NaN₃. In the structure, μ₂‐1,1‐ and μ₃‐1,1,1‐azide anions bridge five Cu^II cations to form a linear pentanuclear cluster unit, which is further linked by μ₂‐1,1‐ and μ₂‐1,3‐azide anions to form a two‐dimensional condensed [Cu₅(N₃)₁₂]_n layer. The diprotonated piperazine and the solvent water molecules are hydrogen bonded to the coordination layers to form a three‐dimensional supramolecular network.     

Room‐temperature RAFT copolymerization of 2‐chloroallyl azide with methyl acrylate and versatile applications of the azide copolymers

A new vinyl azide monomer, 2‐chlorallyl azide (CAA), has been synthesized from commercially available reagent in one step. The reversible addition fragmentation chain transfer (RAFT) copolymerization of CAA with methyl acrylate (MA) was carried out at room temperature using a redox initiator, benzoyl peroxide (BPO)/N,N‐dimethylaniline (DMA), in the presence of benzyl 1H‐imidazole‐1‐carbodithioate (BICDT). The polymerization results showed that the process bears the characteristics of controlled/living radical polymerizations, such as the molecular weight increasing linearly with the monomer conversion, the molecular weight distribution being narrow, and a linear relationship existing between ln([M]₀/[M]) and the polymerization time. Chain extension polymerization was performed successfully to prepare block copolymer. Furthermore, the azide copolymers were functionalized by Cu^I‐catalyzed “click” reaction with alkyne‐containing poly(ethylene glycol) (PEG) to yield graft copolymers with hydrophilic PEG side chains. Surface modification of the glass sheet was successfully achieved via the crosslinking reaction of the azide copolymer under UV irradiation at ambient temperature. © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 48: 1348–1356, 2010     

Poly[(μ2‐aqua‐κ2O:O)(μ3‐azido‐κ3N1:N1:N3)(μ2‐isonicotinato‐κ2O:O′)lead(II)]

In the title compound, [Pb(C₆H₄NO₂)(N₃)(H₂O)]_n, the Pb ion is seven‐coordinated by three N atoms from three azide ligands, two O atoms from two isonicotinate (inic) ligands and two O atoms from two coordinated water molecules, forming a distorted monocapped triangular prismatic coordination geometry. Each azide ligand bridges three Pb^II ions in a μ_1,1,3 coordination mode to form a two‐dimensional three‐connected 6³ topology network extending in the bc plane. The carboxylate group of the inic unit and the aqua ligand act as coligands to bridge Pb^II ions. Adjacent two‐dimensional layers are connected by hydrogen‐bonding interactions between the isonicotinate N atom and the water molecule, resulting in an extended three‐dimensional network. The title complex is the first reported coordination polymer involving a p‐block metal, an azide and a carboxylate.     

Incorporating Si3N4 into PEEK to Produce Antibacterial,Osteocondutive, and Radiolucent Spinal Implants

Polyetheretherketone (PEEK) is a popular polymeric biomaterial which is primarily used as an intervertebral spacer in spinal fusion surgery; but it is developed for trauma, prosthodontics, maxillofacial, and cranial implants. It has the purported advantages of an elastic modulus which is similar to native bone and it can be easily formed into custom 3D shapes. Nevertheless, PEEK's disadvantages include its poor antibacterial resistance, lack of bioactivity, and radiographic transparency. This study presents a simple approach to correcting these three shortcomings while preserving the base polymer's biocompatibility, chemical stability, and elastic modulus. The proposed strategy consists of preparing a PEEK composite by dispersing a minor fraction (i.e., 15 vol%) of a silicon nitride (Si₃N₄) powder within its matrix. In vitro tests of PEEK composites with three Si₃N₄ variants—β‐Si₃N₄, α‐Si₃N₄, and β‐SiYAlON—demonstrate significant improvements in the polymer's osteoconductive versus SaOS‐2 cells and bacteriostatic properties versus gram‐positive Staphylococcus epidermidis bacteria. These properties are clearly a consequence of adding the bioceramic dispersoids, according to chemistry similar to that previously demonstrated for bulk Si₃N₄ ceramics in terms of osteogenic behavior (vs both osteosarcoma and mesenchymal progenitor cells) and antibacterial properties (vs both gram‐positive and gram‐negative bacteria).     

Interaction potential models for bulk Zns,Zns nanoparticle,and Zns nanoparticle‐PMMA from first‐principles

An ab initio derived transferable polarizable force‐field has been developed for Zinc sulphide (ZnS) nanoparticle (NP) and ZnS NP‐PMMA nanocomposite. The structure and elastic constants of bulk ZnS using the new force‐field are within a few percent of experimental observables. The new force‐field show remarkable ability to reproduce structures and nucleation energies of nanoclusters (Zn₁S₁‐Zn₁₂S₁₂) as validated with that of the density functional theory calculations. A qualitative agreement of the radial distribution functions of Zn? O, in a ZnS nanocluster‐PMMA system, obtained using molecular mechanics molecular dynamics (MD) and ab initio MD (AIMD) simulations indicates that the ZnS–PMMA interaction through Zn? O bonding is explained satisfactorily by our force‐field. © 2015 Wiley Periodicals, Inc.     

First-principles study of structural,elastic, electronic and vibrational properties of BiCoO3

We used density functional theory (DFT) to study the structural, elastic, electronic, and lattice dynamical properties of tetragonal BiCoO₃ applying the “norm-conserving” pseudopotentials within the local spin density approximation (LSDA). The calculated equilibrium lattice parameters and atomic displacements are in agreement with the available experimental and theoretical results. Moreover, the structural stability of tetragonal BiCoO₃ were confirmed by the calculated elastic constants. In addition, the elastic properties of polycrystalline aggregates including bulk, shear and Young's moduli, and Poisson's ratio are also determined. The electronic band structure, total and partial density of states (DOS and PDOS) with ferromagnetic spin configuration are obtained. The results show that tetragonal BiCoO₃ has an indirect band gap with both up- and down-spin configurations and its bonding behavior is of covalent nature. We compute Born effective charge (BEC) which is found to be quite anisotropic of Bi, Co and O atoms. The infrared and Raman active phonon mode frequencies at the Г point are found. The phonon dispersion curves exhibit imaginary frequencies which lead from the high-symmetry tetragonal phase to low-symmetry rhombohedral phase in BiCoO₃. The six independent elastic constants, including bulk, shear and Young's moduli, and Poisson's ratio, complete BEC tensor and phonon dispersion relations in tetragonal BiCoO₃ are predicted for the first time. Results of the calculations are compared with the existing experimental and theoretical data.     

Synthesis and characterization of poly(isobutylene‐co‐isoprene)‐derived macro‐monomers

Allylic halide displacement from brominated poly(isobutylene‐co‐isoprene) (BIIR) by carboxylate nucleophiles is used to prepare elastomer derivatives containing pendant polymerizable functionality. These solvent‐borne substitutions are conducted under homogeneous and phase‐transfer catalyzed reaction conditions to synthesize acrylate and vinylbenzoate esters in high yield. The resulting macro‐monomer derivatives are shown to crosslink efficiently with peroxide initiation to give high modulus, thermoset products that cannot otherwise be accessed from isobutylene‐rich elastomers. The extent of cure, as measured by the storage modulus of the vulcanizate, scales with RCH=CH₂ content, and can be extended by co‐oligomerization of pendant unsaturation with that contained within multifunctional coagents. An alternate approach involving the introduction of pendant sulfonyl azide functionality is described, wherein thermal decomposition to nitrene intermediates supports an efficient crosslinking process. © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2010     

First Principles Study of Al-Li Intermetallic Compounds

The structural properties, heats of formation, elastic properties, and electronic structures of four compositions of binary Al-Li intermetallics, Al₃Li, AlLi, Al₂Li₃, and Al₄Li₉, are ana-lyzed in detail by using density functional theory. The calculated formation heats indicate a strong chemical interaction between Al and Li for all the Al-Li intermetallics. In partic-ular, in the Li-rich Al-Li compounds, the thermodynamic stability of intermetallics linearly decreases with increasing concentration of Li. According to the computational single crystal elastic constants, all the four Al-Li intermetallic compounds considered here are mechani-cally stable. The polycrystalline elastic modulus and Poisson's ratio have been deduced by using Voigt, Reuss, and Hill approximations, and the calculated ratios of bulk modulus to shear modulus indicate that the four compositions of binary Al-Li intermetallics are brittle materials. With the increase of Li concentration, the bulk modulus of Al-Li intermetallics decreases in a linear manner.     

Nanoindentation of biodegradable cellulose diacetate‐graft‐poly(L‐lactide) copolymers: Effect of molecular composition and thermal aging on mechanical properties

Nanoindentation of cellulose diacetate‐graft‐poly(lactide)s (CDA‐g‐PLLAs) synthesized by ring opening graft copolymerization of L ‐lactide in bulk onto the residual hydroxyl positions on CDA were conducted to investigate the effect of the molecular composition and thermal aging on mechanical properties and creep behavior. Continuous stiffness measurement (CSM) technique was used to obtained hardness and elastic modulus. These material properties were expressed as a mean value from 100 to 300 nm depths and an unloading value at final indentation depth. The hardness and elastic modulus in all CDA‐g‐PLLAs were higher than those in pure CDA, indicating that the introduction of PLLA increases the hardness and elastic modulus. With an increase of crystallinity by thermal aging, the hardness and elastic modulus were increased in both CDA‐g‐PLLA and PLLA. The creep test performed by CSM showed that the creep strain of CDA was decreased by the grafting of PLLA. Thermal aging decreased the creep strain of CDA‐g‐PLLA and PLLA. With an increase of holding time, hardness was decreased, whereas elastic modulus was kept almost constant. © 2007 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 45: 1114–1121, 2007     

First-principles studies of Al-Ni intermetallic compounds

The structural properties, heats of formation, elastic properties, and electronic structures of Al-Ni intermetallic compounds are analyzed here in detail by using density functional theory. Higher calculated absolute values of heats of formation indicate a very strong chemical interaction between Al and Ni for all Al-Ni intermetallic compounds. According to the computational single crystal elastic constants, all the Al-Ni intermetallic compounds considered here are mechanically stable. The polycrystalline elastic modulus and Poisson's ratio have been deduced by using Voigt, Reuss, and Hill (VRH) approximations, and the calculated ratio of shear modulus to bulk modulus indicated that AlNi, Al₃Ni, AlNi₃ and Al₃Ni₅ compounds are ductile materials, but Al₄Ni₃ and Al₃Ni₂ are brittle materials. With increasing Ni concentration, the bulk modulus of Al-Ni intermetallic compounds increases in a linear manner. The electronic energy band structures confirm that all Al-Ni intermetallic compounds are conductors.