Ionic polymers as a new structural motif for high-energy-density materials

Energetic materials have been used for nearly two centuries in military affairs and to cut labor costs and expedite laborious processes in mining, tunneling, construction, demolition, and agriculture, making a tremendous contribution to the world economy. Yet there has been little advancement in the development of altogether new energetic motifs despite long-standing research efforts to develop superior materials. We report the discovery of new energetic compounds of exceptionally high energy content and novel polymeric structure which avoid the use of lead and mercury salts common in conventional primary explosives. Laboratory tests indicate the remarkable performance of these Ni- and Co-based energetic materials, while DFT calculations indicate that these are possibly the most powerful metal-based energetic materials known to date, with heats of detonation comparable with those of the most powerful organic-based high explosives currently in use.     

Synthesis,structural and spectroscopic properties of two new ethylenediamine-templated gallophosphate-oxalate layered materials

Two new layered gallophosphate-oxalate materials have been prepared hydrothermally using ethylenediamine and oxalic acid as structure-directing agents. The compounds (C2N2H10)2[Ga2(C2O4)2(HPO4)3].H2O 1 and (C2N2H10)3- [Ga4(C2O4)4(HPO4)4(H2PO4)2] 2 are closely related, consisting of anionic double chains built of alternating paris of GaO6 and HPO4 polyhedra. These double chains are linked via bridging HPO4 or H2PO4 tetrahedra to form corrugated layers containing eight-membered rings. The oxalate group acts as a bidentate ligand to each of the GaO6 octahedron. The corrugated layers are held together by strong to weak hydrogen-bonding interactions between oxalate groups, water and diprotonated ethylenediamine molecules, and the framework components. The compounds were characterized by single-crystal X-ray diffraction, thermogravimetric analysis, and infrared and Raman spectroscopy. Crystal data for 1: monoclinic, space group P21/C (No. 14), a = 6.355(1) A, b = 39.362(8) A, c = 9.249(2) A, beta = 106.7(1) degrees, Z = 2. Crystal data for 2: triclinic, space group P1 (No. 2), a = 8.730(1) A, b = 11.575(1) A, c = 11.696(1) A, alpha = 115.12(1) degree, beta = 90.07(1) degree, gamma = 111.23(1) degree, Z = 2.     

Design of new materials for environmental control

During the past several years we have pursued a program here at UIUC to tailor the pore size and surface chemistry of activated carbon fibers (ACFs) to greatly increase their efficiency and selectivity for removal of trace contaminants from the environment. In addition we have evolved new ways of preparing the ACFs to sharply reduce their cost (typically ∼$100/lb) to be more competitive with activated carbon granules ($1-2/lb), but also to greatly improve the abrasion resistance of the fibers. This was accomplished by coating glass fibers with a phenolic resin and then activating the coating under a controlled atmosphere to produce a variety of tailored micropores. Using chemically tailored ACFs, we describe major improvements over current activated carbons for adsorption of environmental contaminants.     

Construction of heterostructure materials toward functionality

One- and zero-dimensional organic/inorganic heterostructure materials have been attracting considerable attention in materials science because of their outstanding optical and electrical properties and high tailorability in terms of composition, structure, and morphology. Strong interactions between the organic and inorganic units can lead to novel or improved physical or chemical performance relative to that of the individual components, thereby realizing synergistic ("1 + 1 > 2") performance. In this tutorial review, we discuss the synthetic methods available for preparing heterostructures incorporating diverse components; the functionality of the heterostructure materials; and their potential applications in the fields of electronics, optics, biology, and catalysis. The future development of such heterostructure materials will require deeper understanding of organic-inorganic or organic-organic interfaces on the nanoscale, collective phenomena, and interparticle coupling.     

Property control of new forms of carbon materials by fluorination

Multiwall carbon nanotubes (MWNTs) based on the template carbonization technique were fluorinated in a temperature range 323-473 K by elemental fluorine. The fluorination of the carbon nanotubes results in functionalization and modification of pristine nanotubes with respect to adsorption and electrochemical properties. Selective fluorination of the inner surface of the carbon nanotubes, brings about a decrease in the surface free energy of the inner surface of the tubes and an increase in colombic efficiency of Li/nanotubes rechargeable cells in an aprotic medium. Electrochemical fluoride-ion doping of fullerene C₆₀ thin films (250-450 nm) was carried out in a fluoride-ion conductive solution, MeCN solution of 1 M Et₄NF·4HF. Galvanostatic oxidation yielded C₆₀F_ca.1-3 where fluorine exists as a semi-ionic species in the cavity surrounded by C₆₀ molecules without forming covalent CF bonds     

Tin-based hybrid materials with a two-level structural hierarchy

Self-assembled tin-based hybrid materials with two levels of hierarchy were obtained spontaneously from the hydrolysis of hexaalkynylorganoditins bridged with an aromatic spacer, while in the case of an aliphatic spacer this phenomenon occurred only in the presence of a surfactant.     

General silaindene synthesis based on intramolecular reductive cyclization toward new fluorescent silicon-containing pi-electron materials

[reaction: see text] The reaction of (o-silylphenyl)acetylene derivatives with lithium naphthalenide undergoes intramolecular reductive cyclization to produce various silaindene derivatives. On the basis of this methodology, a series of silaindene-containing pi-electron systems are synthesized that show intense blue to greenish-blue fluorescence.     

Corrosion resistance of a number of structural materials in a NaOH melt

Corrosion resistance of copper, nickel, and a number of alloys in a NaOH melt in the atmosphere of argon was studied in the temperature range 400–700°C.     

Examination of materials with the mobile thermal microscope ALADIN,a new analytical tool of materials technology

Frequency-modulated optical beams—preferentially laser beams—can excite temperature-modulated thermal waves in a material; their properties are described. Photothermal methods can be used to determine properties of materials at and/or below the surface. The working principle of the thermal microscope ALADIN (advancedlaser-aideddefectinspection innon-destructive testing) is explained; this instrument (developed by Siemens/KWU in collaboration with Phototherm Dr. Petry GmbH/Saarbrücken) provides the user with a flexible, high performance system of modular design. The most important features are mobility, compact design of the sensor and its suitability for use under extremely ambient conditions, e.g. field metallography in power plants. The equipment allows scanning of an area up to 25 mm² with a lateral resolution in the micrometer range. Some examples are given; one of the main applications will be the determination of fatigue or creep damages at metal surfaces.Dedicated to Professor Günther Tölg on the occasion of his 60th birthday     

Sorption capacity of lignocellulosic materials toward humic acids

Russian Chemical Bulletin - Sorption capacity toward humic acids was studied for a number of lignocellulosic materials with different structures and chemical compositions. The values of sorption...     

Size, shape, and structural control of metallic nanocrystals

In this review, we show that chemical reduction in colloidal assemblies favors the formation of size- and shape-controlled metallic nanoparticles. The key parameters that make possible the size control of spherical nanoparticles produced in spherical reverse micelles are the degree of hydration of the reactants, the dynamic character of the micelles, the capping with the surfactant, and the reducing agent concentration. The particle shape can be controlled by combining the strategy of the surfactant-based template and the capping of salts or molecules. Proof of the quality of the samples is given by the observation of two- and three-dimensional spontaneous self-organizations.     

Methylx derivatives of tetrahydrobenzo- and benzofurocoumarins,a new class of potential photoreagents toward dna

A number of new tetracyclic furocoumarin derivatives with a linear structure or with various angular arrangements, were synthetized. The new compounds are characterized for having an additional cyclohexene or phenyl ring condensed at the 4′,5′ double bond of the furan ring of the furocoumarin nucleus. The syntheses were performed starting from the appropriate hydroxycoumarins on which the tetrahydrobenzofuran or benzofuran moiety was built. Methyl groups have been introduced into positions which look most promising for enhancement of the photoreactivity of the compounds toward DNA.     

Multifunctional polyesters as new candidate materials for biomedical applications. Synthesis and structural characterization

The present work was aimed at the development of functional polymeric materials to be used in the targeted delivery of proteic drug and tissue engineering fields. The adopted strategy was based on the design of special polymer classes whose structures and functionality could be easily modified by finely tuned synthetic procedures. Poly(ether ester)s containing H-bonding units were chosen as promising materials for the proposed applications. Commercially available precursors were successfully used for the synthesis of symmetrical diesters containing different H-bonding groups (amide, carbamate, and urea moieties). In all cases, pure products were obtained in good yields. Bulk polycondensation of the monomeric precursors with different mixtures of 1,4-butanediol and PEG 1000 diol afforded a variety of high molecular weight polymeric structures. Physical-chemical characterization of the polymers indicates that their thermal, mechanical, and swelling properties can be tailored by a proper selection of the H-bonding group and of the composition of the feed mixture.     

Synthesis, structural characterization, and molecular modeling of dodecaniobate keggin chain materials

Four new isostructural one-dimensional dodecaniobate Keggin materials, Na12[Ti2O2][TNb12O40] x xH2O and Na10[Nb2O2][TNb12O40] x xH2O with T = (Si or Ge), have been synthesized hydrothermally using a Lindqvist-ion salt, Na7[Nb6O19H] x 15H2O, as the precursor. Their structure, consisting of chains of Keggin ions [TNb12O40]16- linked by [Ti2O2]4+ or [Nb2O2]6+ bridges, was solved ab initio from powder diffraction data. The location of the charge-balancing sodium atoms and the water molecules was further investigated by molecular simulations. These compounds were also characterized by IR and solid-state 1H, 29Si, and 23Na MAS NMR spectroscopies. The structural relationships between these and related phases based on similar Keggin ion building units are discussed.     

Synthesis and structural evolution of rusb3, a new metastable skutterudite compound

A thin-layer synthesis technique was used to synthesize bulk amounts of the metastable phase, RuSb(3), a novel compound with the skutterudite structure. The compound crystallized at 350 degrees C and was stable to 525 degrees C. When annealed above 550 degrees C, it decomposed into RuSb(2) and Sb. Rietveld refinement of X-ray diffraction data showed the presence of excess Sb residing in the interstitial site in the skutterudite structure. X-ray diffraction and thermal analysis experiments allowed us to examine the evolution of the sample as a function of annealing and determine the reaction pathway. The activation energy for the crystallization of the compound was determined to be 3 eV/nucleation event, while the activation energy for decomposition was approximately 8 eV.     

Synthesis,structural characterization,and thermal properties of a new energetic zinc-FOX-7 complex

A new energetic zinc-FOX-7 complex (FOX-7 = 1,1-diamino-2,2-dinitroethylene), Zn(NH₃)₂(FOX-7)₂, was synthesized and structurally characterized by single crystal X-ray diffraction. Zn²⁺ was coordinated by four nitrogens from two ammonias and two FOX-7^? anions, forming a distorted tetrahedron. Thermal decomposition of Zn(NH₃)₂(FOX-7)₂ was studied by differential scanning calorimetry and thermogravimetry/differential thermogravimetry. The apparent activation energy and pre-exponential constant of the first decomposition process are 144.8 kJ M^?1 and 10^13.99?s^?1, respectively. The self-accelerating decomposition temperature and critical temperature of thermal explosion of Zn(NH₃)₂(FOX-7)₂ are 183.2 and 195.8?°C, respectively. The thermal stability of Zn(NH₃)₂(FOX-7)₂ is good, but Zn(NH₃)₂(FOX-7)₂ is still sensitive.     

Cyclic dialkylindium amides: new structural information and ultra-purification using inorganic and inorgano-organic layered materials

New data on some cyclic dimethyl- and diethylindium-amides were obtained. X-ray structure of pyrrolidinodimethylindium was determined. The molecule is centrosymmetric with square-planar In₂N₂ base and distorted tetrahedral metal environment similar to that of known dialkylindium amides, the cyclic amido-ligands are present in an envelope conformation. A novel material- and energy-saving procedure for sorption ultra-purification of highly sensitive organometallic compounds in absolute non-polar media was developed. Advanced inorganic and inorgano-organic crystalline layered materials possessing enhanced affinity towards selected ions or molecules were applied for the sorption treatment.     

At the crossroads of chemistry, biology, and materials: structural DNA nanotechnology

Structural DNA nanotechnology consists of combining unusual DNA motifs by specific structurally well-defined cohesive interactions (primarily sticky ends) to produce target materials with predictable 3D structures. This effort has generated DNA polyhedral catenanes, robust nanomechanical devices, and a variety of periodic arrays in two dimensions. The system has been used to produce specific patterns on the mesoscale through designing and combining specific DNA strands, which are then examined by atomic force microscopy. The combination of these constructions with other chemical components is expected to contribute to the development of nanoelectronics, nanorobotics, and smart materials. The organizational capabilities of structural DNA nanotechnology are just beginning to be explored, and the field is expected ultimately to be able to organize a variety of species that will lead to exciting and possibly revolutionary materials.     

Cyclopentathiadiazines, new heterocyclic materials from cyclic enaminonitriles

Indene and cyclopentene enaminonitriles were reacted with SCl2, iBu3N and NCS to give the first cyclopenta[1,2,6]thiadiazines that showed unusual characteristics, one as a NIR dye and another as a liquid crystal.     

Rare-earth quinolinates: infrared-emitting molecular materials with a rich structural chemistry

Near-infrared-emitting rare-earth chelates based on 8-hydroxyquinoline have appeared frequently in recent literature, because they are promising candidates for active components in near-infrared-luminescent optical devices, such as optical amplifiers, organic light-emitting diodes, .... Unfortunately, the absence of a full structural investigation of these rare-earth quinolinates is hampering the further development of rare-earth quinolinate based materials, because the luminescence output cannot be related to the structural properties. After an elaborate structural elucidation of the rare-earth quinolinate chemistry we can conclude that basically three types of structures can be formed, depending on the reaction conditions: tris complexes, corresponding to a 1:3 metal-to-ligand ratio, tetrakis complexes, corresponding to a 1:4 metal-to-ligand ratio, and trimeric complexes, with a 3:8 metal-to-ligand ratio. The intensity of the emitted near-infrared luminescence of the erbium(III) complexes is highest for the tetrakis complexes of the dihalogenated 8-hydroxyquinolinates.