Novel high-nitrogen materials based on nitroguanyl-substituted tetrazines

The synthesis and properties of several novel high-nitrogen materials based on nitroguanyl-substituted tetrazines are described. An optimized procedure provides straightforward access to these materials in multigram quantities.     

Novel architectures of boron

Structural Chemistry - The review presents results of the recent studies of non-typical forms of boron derivatives, including flat hexagonal boron, boron fullerenes, supertetrahedral boron, and...     

Broadband radio-absorbing materials based on porous composites with carbon nanotubes

The reflection coefficient of an electromagnetic wave has been theoretically studied as a function of the thickness of a material and its dielectric properties. Samples based on spheroplastics with noncovalently modified carbon nanotubes have been obtained. The radio-engineering and electrophysical properties of these composites are discussed as well. The prospects for applying porous nanocomposites with carbon nanotubes in the fabrication of radio-absorbing materials are also shown.     

Electroosmosis in porous materials

Electroosmosis is the phenomenon of fluid flow induced by an applied electric field. This paper is concerned with electroosmosis in a porous material composed of closely-packed spheres immersed in a general electrolyte. A formula is obtained for the electroosmotic flow rate in the case when the double layer is much thinner than the particle radius. By combining this formula with electroosmosis measurements it is possible to determine the particle ζ potential. To test the validity of the model which underlies this, and most other electrokinetic calculations, ζ potentials obtained from Van der Put and Bijsterbosch's (J. Colloid Interface Sci. 92, 499, 1983) electroosmosis measurements are compared with potentials obtained from their conductivity and electrophoresis measurements.     

Structure and properties of porous film materials based on an aliphatic copolyamide

Phase segregation of solutions of ɛ-caprolactam-polyhexamethyleneadipamide copolymer in alcoholwater mixtures and the influence exerted on the pore structure and properties of film materials by the solution concentration and time of its keeping prior to deposition were studied.     

Positronium chemistry in porous materials

Porous materials have fascinated positron and positronium chemists for over decades. In the early 1970s it was already known that ortho-positronium (o-Ps) exhibits characteristic long lifetimes in silica gels, porous glass and zeolites. Since then, our understanding of Ps formation, diffusion and annihilation has been drastically deepened. Ps is now well recognized as a powerful porosimetric and chemical probe to study the average pore size, pore size distribution, pore connectivity and surface properties of various porous materials including thin films. In this paper, developments of Ps chemistry in porous materials undertaken in the past some 40 yr are surveyed and problems to be addressed in future are briefly discussed.     

New supramolecular architectures based on hydrogen bonding

Heterocyclic compounds containing two and three adjacent hydrogen bond donor and acceptor sites in all possible arrangements were synthesized (see generalized structures shown below) to study and use their “base-pairing” capabilities. With two adjacent donor and acceptor groups there are three possible arrangements and these form two types of complexes (DA·AD and AA·DD). Three adjacent hydrogen bond donor and acceptor sites can be arranged in six different ways and these form three different complexes (ADA·DAD, AAD·DDA, and AAA·DDD).     

From controlled 3-dimensional architectures to smart materials

Under the pressure of bad economic conditions, Chemical Industry and the Polymer Producing Industry in particular, have been focusing on core businesses and several developments in advanced materials have been slowed down. Increased competition from low cost countries imposes rigorous restructuring of the traditional industry. Environmental considerations enhance the pressure even more. While the Polymer Industry is struggling with major restructuring operations, the scientific activities in the field of macromolecules show a tremendous innovative power. Ever increasing molecular control by the use of new catalysts, cooperative supramolecular interactions and controlled building up of 3-dimensional structures, new architectures leading to enhanced performance and completely new properties, development of functional materials and smart materials are hot items at every meeting. The outcome of this situation could be that the world of materials and materials producers will look quite different in the first decade of the next century.     

Novel porous polyurethane films

Polyurethane films treated in a two-stage process with aqueous bromine and ammonia solutions underwent significant modifications in crystalline and surface structure as well as in mechanical and physical properties. Bromine was sorbed on the film, and formed several charge transfer complexes with the soft and hard segments of the polyurethane as well as bridges between adjacent chains. In the second stage, ammonia reacted with the sorbed bromine producing gaseous nitrogen and ammonium bromide. The expansion of the gas resulted in a repacking of the polymeric chains and the formation of a porous structure. The bromine concentrations used and the times of contact between the films and the bromine were 0.02–0.06 normal and 1–10 min, respectively. The contact angle of the films decreased, depending on treatment conditions, from 73 to 20. The water vapor permeability increased three-fold. The treatment appeared to bring about a crystallization in the hard as well as in the soft segments of the PU as shown by differential scanning calorimetry measurements. Possible applications of the treated films for wound dressing are discussed. © 1998 John Wiley & Sons, Ltd.     

Novel magnetic materials based on semiconducting 1111 phases: Theory and experiment

Journal of Structural Chemistry - A brief review of theoretical and experimental studies devoted to the design of novel magnetic materials based on non-magnetic semiconductor phases with the...     

Novel linear and tri-branched copolymers based on triphenylamine for non-doping emitting materials

Novel linear and tri-branched copolymers with triphenylamine and cyano groups in the main chain were synthesized by a concise route and an environment-friendly procedure without metal catalyst. They show strong fluorescence in solid state and can be used as non-doping emitter to fabricate emitting diodes. The single-layer electroluminescence devices with PVK or PEDOT buffer layer have been made with these copolymers as non-doping red-orange emitter, electron-transporting as well as hole-transporting material. The single-layer devices show preliminary results with maximum efficiency of 0.052% and EL wavelengths around 614 nm.     

Novel porphyrin-quinone architectures via 1,3-dipolar cycloaddition reactions

Porphyrinic pyridinium ylides react with 1,4-benzoquinone and 1,4-naphthoquinone to afford novel meso-substituted indolizine porphyrins.     

Borromean-entanglement-driven assembly of porous molecular architectures with anion-modified pore space

A series of metal-organic frameworks based on a flexible, highly charged Bpybc ligand, namely 1?Mn?OH(-), 2?Mn?SO(4)(2-), 3?Mn?bdc(2-), 4?Eu?SO(4)(2-) (H(2)BpybcCl(2) = 1,1'-bis(4-carboxybenzyl)-4,4'-bipyridinium dichloride, H(2)bdc = 1,4-benzenedicarboxylic acid) have been obtained by a self-assembly process. Single-crystal X-ray-diffraction analysis revealed that all of these compounds contained the same n-fold 2D→3D Borromean-entangled topology with irregular butterfly-like pore channels that were parallel to the Borromean sheets. These structures were highly tolerant towards various metal ions (from divalent transition metals to trivalent lanthanide ions) and anion species (from small inorganic anions to bulky organic anions), which demonstrated the superstability of these Borromean linkages. This non-interpenetrated entanglement represents a new way of increasing the stability of the porous frameworks. The introduction of bipyridinium molecules into the porous frameworks led to the formation of cationic surface, which showed high affinities to methanol and water vapor. The distinct adsorption and desorption isotherms of methanol vapor in four complexes revealed that the accommodated anion species (of different size, shape, and location) provided a unique platform to tune the environment of the pore space. Measurements of the adsorption of various organic vapors onto framework 1?Mn?OH(-) further revealed that these pores have a high adsorption selectivity towards molecules with different sizes, polarities, or π-conjugated structures.     

Shape-controlled fabrication of porous ZnO architectures and their photocatalytic properties

In this paper, we report a simple two-step approach to prepare porous octahedron- and rod-shaped ZnO architectures. The morphology of porous ZnO particles can be conveniently tuned by controlling morphologies of the ZnC₂O₄·2H₂O precursor. SEM and TEM characterization results indicate that these porous ZnO architectures are built up by numerous ZnO primary nanoparticles with random attachment. Based on thermogravimetry analysis, we believe that the release of water vapor, CO and CO₂ leads to the formation of high-density pores in shape-controlled particles during the calcination process. Further experimental results indicate that as-prepared porous ZnO particles exhibit good photocatalytic activity due to large surface area.     

Prediction of adsorption of small molecules in porous materials based on ab initio force field method

Computational prediction of adsorption of small molecules in porous materials has great impact on the basic and applied research in chemical engineering and material sciences. In this work,we report an approach based on grand canonical ensemble Monte Carlo(GCMC) simulations and ab initio force fields. We calculated the adsorption curves of ammonia in ZSM-5 zeolite and hydrogen in MOF-5(a metal-organic-framework material). The predictions agree well with experimental data. Because the predictions are based on the first principle force fields,this approach can be used for the adsorption prediction of new molecules or materials without experimental data as guidance.