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Interesting Class (interesting + class)
Selected AbstractsSynthesis and Characterisation of a New Cu(O2CNAllyl2)2 Carbamato Complex and an Unusual Polymeric CuI Complex [CuI4Cl4(NHAllyl2)4]n: New Insights into Metal Carbamato ChemistryEUROPEAN JOURNAL OF INORGANIC CHEMISTRY, Issue 35 2009Alberto Albinati Abstract Transition-metal N,N -dialkylcarbamato complexes represent an interesting class of compounds that can be conveniently used as precursors for the controlled formation of inorganic compounds, typically oxides. They can also be used as convenient precursors for chemical grafting of metal oxides on oxide surfaces as well as for the synthesis of inorganic,organic hybrid materials. In this last case, the presence of double bonds on the complex would enable its covalent embedding into a polymer matrix through reaction with suitable monomers. To this aim, we addressed the synthesis of an allyl-functionalised copper carbamato complex. During the synthesis of the N,N -diallylcarbamato complex Cu(O2CNAllyl2)2 (Cu1), the formation of the crystalline and unusual polymeric CuI complex [CuI4Cl4(NHAllyl2)4]n (Cu2) was observed. The new compound was characterised by X-ray single crystal diffraction and FTIR, 1H and 13C NMR spectroscopic analysis. In an attempt to investigate the redox mechanism and the equilibria leading to the formation of the observed unusual CuI polymeric complex, gas chromatography coupled with mass spectrometry (GC,MS) experiments were carried out, which allowed us to identify 3,4-dimethylpyrrole as the oxidation product of the reaction, leading to the reduction of CuII to CuI.(© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2009) [source] Organosilica Materials with Bridging Phenyl Derivatives Incorporated into the Surfaces of Mesoporous Solids,ADVANCED FUNCTIONAL MATERIALS, Issue 8 2008Andreas Kuschel Abstract An interesting class of materials is mesoporous organosilica materials containing a bridging, organic group along the pore-surface. Such materials are prepared from silsesquioxane precursors of the type (R,O)3Si-R-Si(OR,)3 where R is the bridging organic group of interest, in combination with a lyotropic phase as a template for the generation of the pores. A new silsesquioxane precursor, 1,3-bis-(trialkoxysilyl)-5-bromobenzene, and the related mesoporous organosilica material containing bromobenzene groups located at the pore walls are presented in the current publication. The latter precursor allows access to the derivatization reactions known for halogenated aromatic compounds. Materials containing phenyl derivatives can be obtained either by chemical modifications starting from the mentioned precursor on the molecular scale, or the modifications can be performed directly at the surfaces of the porous material. Materials with surfaces containing benzoic acid, styrene, and phenylphosphonic acid are described. [source] A Novel Bis-Thiourea Organocatalyst for the Asymmetric Aza-Henry ReactionADVANCED SYNTHESIS & CATALYSIS (PREVIOUSLY: JOURNAL FUER PRAKTISCHE CHEMIE), Issue 11-12 2008Constantinos Rampalakos Abstract A novel bis-thiourea/2,2,-diaminobinaphthalene (BINAM)-based catalyst for the asymmetric aza-Henry reaction has been developed. This catalyst promotes the reaction of N -Boc imines with nitroalkanes to afford ,-nitroamines with good yields and high enantioselectivities. This catalyst has the advantage that it can be prepared in a single step from commercially available materials. A model is proposed for the catalyst action where both components of the reaction are activated simultaneously by hydrogen bonding. Regardless of the mechanism, the success of the present catalyst demonstrates the potential of bis-thioureas as an interesting class of relatively unexplored catalysts. [source] Synthesis and characterization of a series of diverse poly(2-oxazoline)sJOURNAL OF POLYMER SCIENCE (IN TWO SECTIONS), Issue 15 2009Kristian Kempe Abstract This article describes the synthesis and characterization of a variety of new poly(2-oxazoline)s. With regard to functional polymers, 2-oxazolines represent an interesting class of monomers because of the easy variation of the substituent in 2-position. Starting from the corresponding nitriles, different 2-oxazolines were obtained containing a diverse set of 2-substituents, including thioether bonds (M11), trifluoromethyl groups (M8, M10), and alkyl- or aryl groups (M1,M7). The subsequent polymerization of the majority of these monomers proceeded in a living manner, which was demonstrated by linear first-order kinetics, a linear increase of molar mass with conversion, and relatively narrow molar mass distributions. In addition, selected thermal and surface properties of the polymers were studied utilizing DSC and contact-angle measurements to determine the effects of different 2-substituents on the macroscopic properties. © 2009 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 47: 3829,3838, 2009 [source] Synthesis and characterization of hydrogels containing biodegradable polymersPOLYMER INTERNATIONAL, Issue 7 2008Adina Cretu Abstract BACKGROUND: Amphiphilic block and graft copolymers constitute a very interesting class of polymers with potential for biomedical applications, due to their special characteristics, which derive from the combination of properties of hydrophilic and hydrophobic moieties. In this work, the synthesis and biodegradation of poly(2-hydroxyethyl methacrylate)- graft -poly(L -lactide) are studied. RESULTS: The graft copolymers were synthesized using the macromonomer technique. In a first step, methacryloyl-terminated poly(L -lactide) macromonomers were synthesized in a wide molecular weight range using different catalysts. Subsequently, these macromonomers were copolymerized with 2-hydroxyethyl methacrylate in order to obtain a graft copolymer. These new materials resemble hydrogel scaffolds with a biodegradable component. The biodegradation was studied in hydrolytic and enzymatic environments. The influence of different parameters (molecular weight, crystallinity, ratio between hydrophilic and hydrophobic components) on the degradation rate was investigated. CONCLUSION: Based on this study it will be possible to tailor the release properties of biodegradable materials. In addition, the materials will show good biocompatibility due to the hydrophilic poly(2-hydroxyethyl methacrylate) hydrogel scaffold. This kind of material has potential for many applications, like controlled drug-delivery systems or biodegradable implants. Copyright © 2008 Society of Chemical Industry [source] The Random-Facet simplex algorithm on combinatorial cubes,RANDOM STRUCTURES AND ALGORITHMS, Issue 3 2002Bernd Gärtner The RANDOM -FACET algorithm is a randomized variant of the simplex method which is known to solve any linear program with n variables and m constraints using an expected number of pivot steps which is subexponential in both n and m. This is the theoretically fastest simplex algorithm known to date if m , n; it provably beats most of the classical deterministic variants which require exp(,(n)) pivot steps in the worst case. RANDOM -FACET has independently been discovered and analyzed ten years ago by Kalai as a variant of the primal simplex method, and by Matous,ek, Sharir, and Welzl in a dual form. The essential ideas and results connected to RANDOM -FACET can be presented in a particularly simple and instructive way for the case of linear programs over combinatorialn - cubes. I derive an explicit upper bound of (1) on the expected number of pivot steps in this case, using a new technique of "fingerprinting" pivot steps. This bound also holds for generalized linear programs, similar flavors of which have been introduced and studied by several researchers. I then review an interesting class of generalized linear programs, due to Matous,ek, showing that RANDOM -FACET may indeed require an expected number of pivot steps in the worst case. The main new result of the paper is a proof that all actual linear programs in Matous,ek's class are solved by RANDOM -FACET with an expected polynomial number of pivot steps. This proof exploits a combinatorial property of linear programming which has only recently been discovered by Holt and Klee. The result establishes the first scenario in which an algorithm that works for generalized linear programs "recognizes" proper linear programs. Thus, despite Matous,ek's worst-case result, the question remains open whether RANDOM -FACET (or any other simplex variant) is a polynomial-time algorithm for linear programming. Finally, I briefly discuss extensions of the combinatorial cube results to the general case. © 2002 Wiley Periodicals, Inc. Random Struct. Alg., 20:353,381, 2002 [source] Biopolymere in textilen Anwendungen.CHEMIE IN UNSERER ZEIT (CHIUZ), Issue 3 2009Polyhydroxyalkanoate, Polylactid Abstract Biopolymere stellen eine interessante Polymerklasse dar, deren Potential bisher noch nicht endgültig erfasst ist. Sie gewinnen jedoch zunehmend an Marktwert. Vor allem Polylactid (PLA) hat sich bereits durchsetzen können, da es nicht nur aus nachwachsenden Rohstoffen hergestellt werden kann und abbaubar ist, sondern darüber hinaus ein Eigenschaftsprofil aufweist, das mit herkömmlichen thermoplastischen Kunststoffen vergleichbar ist und sich auch ähnlich gut verarbeiten lässt. Das Anwendungsfeld der Biopolymere reicht von Folien, Obst- und Gemüseschalen bis hin zu Hygiene- und Medizinartikeln und ist daher sehr vielfältig. Diese Vielfältigkeit wird sicherlich in der Zukunft weiter zunehmen. Biopolymers represent an interesting class of polymers whose potential is not yet been fully realised. However, more recently, biopolymers are gaining impetus in the market. Among the biopolymers, polylactic acid (PLA) is being used successfully and is widely accepted because it is produced from natural raw material and is degradable. Furthermore, it has comparable properties to standard thermoplastic polymers and can also be processed using similar process channels as conventional thermoplastic synthetic materials. Biopolymer applications are manifold and range from foils, fruit and vegetable packaging to hygiene and medical products. It can be expected that in future the application spectrum of biopolymers will increase even further. [source] | |||||||||||||