Effect of the Drawing Process on the Thermal Stability of Gelatine-polyacrylonitrile Graft Copolymer Fibres

The thermal stability of gelatine-polyacrylonitrile graft copolymers fibres obtained under various conditions of deformation has been studied. The thermal properties of examined fibres depend on the synthetic component of the fibre forming material – polyacrylonitrile which appears in the form of grafted PAN chains and PAN homopolymer. It was stated that the highest thermal stability have those fibres which formation process included two stages of drawing with the use of deformation close to the maximal values, with the value of the total draw ratio amounting to 691%. It should be supposed that with such a drawing process, already in its first stage, are created advantageous conditions for the formation of paracrystalline regions to a larger extent and their orientation along the fibre axis. This revised version was published online in August 2006 with corrections to the Cover Date.     

Thermal properties and flammability of fibres made from polyimidoamide nanocomposite

The effects of basic fibre-forming parameters on the thermal properties and flammability of fibres from polyimidoamide (PIA) nanocomposite have examined. The comparative analysis of the properties of fibres from modified PIA and PIA nanocomposite has been conducted. The multi-functional fibres prepared from PIA nanocomposite show increased porosity and sorption properties as well as a high thermal stability and reduced flammability in comparison with fibres without MMT.     

Bulk and surface composition, amorphous structure, and thermocrystallization of electrodeposited alloys of tungsten with iron, nickel, and cobalt

It has been shown for iron-group alloys of tungsten, using ESCA spectroscopy of samples sputtered with argon ions and SEM/EDS analysis, that no oxygen is present in the alloy bulk. A very weak internal organization in the alloys, which follows from low and wide diffractograms usually obtained for electrodeposited layers, is thought to be a heavily distorted structure of the major metal component of the alloy. Thermal crystallization of thin layers of the amorphous tungsten alloys does not lead to formation of well-known intermetallic crystal structures. Received: 19 January 1998 / Accepted: 17 July 1998     

Molecular interactions in 3-carboxy-2-diphenylphosphinoylcyclopentanone

The results of the X-ray structure analysis of the title compound (I) have been reported in [Synthesis (1997) 356]. Now we continue our efforts to understand the energy situation and the arrangements in the crystal, which will be strongly influenced by the formation of hydrogen bonds with the help of the results of theoretical calculations. Furthermore, the IR spectroscopic measurements will be discussed in comparison to the X-ray data. The IR experiments elucidate the molecular arrangement in solution. Using different solvents, equilibrium states with coexisting conformational and associative arrangements were observed. Unexpectedly, the alternative use of the solvents CHCl(3) or CDCl(3) has different influence on the equilibrium arrangement of I in solution.     

Selective Hydrosilylation of Alkynes with Octaspherosilicate (HSiMe2O)8Si8O12

Comprehensive studies on platinum‐catalyzed hydrosilylation of a wide range of terminal and internal alkynes with spherosilicate (HSiMe₂O)₈Si₈O₁₂ ( 1 a ) were performed. The influence of the reaction parameters and the types of reagents and catalysts on the efficiency of the process, which enabled the creation of a versatile and selective method to synthesize olefin octafunctionalized octaspherosilicates, was studied in detail. Within this work, twenty novel 1,2‐(E)‐disubstituted and 1,1,2‐(E)‐trisubstituted alkenyl‐octaspherosilicates ( 3 a – m , 6 n – t ) were selectively obtained with high yields, and fully characterized (¹H, ¹³C, ²⁹Si NMR, FTIR, MALDI TOF or TOF MS ES⁺ analysis). Moreover, the molecular structure of the compound (Me₃Si(H)C=C(H)SiMe₂O)₈Si₈O₁₂ ( 3 a ) was determined by X‐ray crystallography for the first time. The developed procedures are the first that allow selective hydrosilylation of terminal silyl, germyl, aryl, and alkyl alkynes with 1 a , as well as the direct introduction of sixteen functional groups into the 1 a structure by the hydrosilylation of internal alkynes. This method constituted a powerful tool for the synthesis of hyperbranched compounds with a Si?O based cubic core. The resulting products, owing to their unique structure and physicochemical properties, are considered novel, multifunctional, hybrid, and nanometric building blocks, intended for the synthesis of star‐shaped molecules or macromolecules, as well as nanofillers and polymer modifiers. In the presented syntheses, commercially available reagents and catalysts were used, so these methods can be easily repeated, rapidly scaled up, and widely applied.     

Diastereomers of N-alpha-phenylethyl-t-butylsulfinamide: absolute configurations and predominant conformations

N-alpha-Phenylethyl-t-butylsulfinamide is a complicated system for determining molecular stereochemistry because of numerous possibilities for assigning the absolute configuration and a predominant conformation. Two diastereomers of N-alpha-phenylethyl-t-butylsulfinamide derived from (-)-(S)-alpha-phenylethyl amine, a (+)-diastereomer and a (-)-diastereomer, have been synthesized and their experimental chiroptical spectroscopic properties have been measured. These properties include vibrational circular dichroism, electronic circular dichroism and optical rotatory dispersion. Using these experimental data, in conjunction with corresponding density functional theoretical predictions, the absolute configuration and predominant conformations of these two diastereomers have been determined. Also, the absolute configuration of (-)-diastereomer has been independently confirmed by determining its structure from X-ray diffraction data.     

Enzymatic Apporoach to the Synthesis of Non-Racemic,P-Chiral Hydroxymethylphosphonates and Phosphinates

Abstract

α-Hydroxyalkanephosphonates and phosphinates exhibit interesting biologd achvlty whch IS highly dependent on theu absolute configumon Therefore, a search for efficient and general methods of the synthesis of enantlopure htle compounds continues As part of our studies on the use of enzymes in preparahon of non-racemic heteroorganic compounds,2 we have developed a hpasemediated lunebc resoluhon of racemic hydroxy- methylphosphonates and phosphinates, which is based on ather acetylatlon of the substrates 1, or hydrolysis of thar O-acetyl denvatlves 2 The absolute configurahon of the products has been determined by means of CD and chemical conelatlon