In-situ measurement of photochemical changes of solid samples by fourier transform infrared photoacoustic spectroscopy

Infrared spectral changes of lithographic printing plates were measuredin-situ by PAS and RAS. The advantages of PAS over RAS were discussed for the spectral measurements of organic coatings on roughened metal surface.     

Ungest?rte Kettendimensionen von stereoirregul?rem 1.4-Polybutadien und 1.4-Polyisopren

Ohne Zusammenfassung     

Preparation of chiral 5-deazaflavin derivatives and their asymmetric reduction of ethyl benzoylformate

1,5-Dihydro-5-deazaflavin derivatives possessing a chiral substituent at N(3) position were synthesized, with which moderate asymmetric induction was observed in the reduction of ethyl benzoylformate.     

New generation of thiocarbonyl ylide and its 1,3-cycloaddition leading to tetrahydrothiophene derivatives

Thiocarbonyl ylide was found to be generated by thermolysis of bromo(trimethylsilylmethylthio)methyltrimethylsilane and its 1,3-cyclo-addition provided a new method for synthesis of tetrahydrothiophenes.     

DMPM (3,4-dimethoxybenzyl) protecting group for hydroxy function more readily removable than MPM (P-methoxybenzyl) protecting group by DDQ oxidation

The DMPM (3,4-dimethoxybenzyl) protection for hydroxy function was deprotected more readily than the MPM (p-methoxybenzyl) protection by DDQ oxidation under neutral conditions, and applied to the synthesis of some synthons to macrolide and polyether antibiotics.     

Pulsed NMR observation of ultradrawn polypropylene

Proton spin-spin relaxation times have been measured as a function of temperature for ultradrawn polypropylene with draw ratios λ up to 24. The three relaxation times T_2a (the longest), T_2i (intermediate), and T_2c (the shortest), observed for all the samples, have been ascribed to the relaxations of the amorphous, constrained amorphous, and crystalline components, respectively. T_2i and T_2a, which reflect the changes in structure and mobility in the noncrystalline regions, decrease with increasing λ; T_2i becomes saturated at λ > 9, whereas T_2a shows a substantial decrease up to λ = 24. The continued decrease in T_2a indicates that the constraint on the amorphous segments keeps increasing up to the highest λ. The associated mass fractions F_a, F_i, and F_c also change with λ. At λ < 9, the increasc in F_i with increasing λ is accompanied by a decrease in F_a, with F_c remaining unchanged. At higher λ, however, F_a is almost constant, and stepwise rises in F_c at about λ = 12 and 24 are accompanied by corresponding drops in F_i. It seems that, in this high draw ratio range, some of the taut molecules are fully extended and are in sufficiently good lateral register to transform into crystalline bridges. This conjecture is supported by the similarity in the λ dependence of F_c and the mass-fraction crystallinity obtained from the heat of fusion.     

NMR study of μc-Si:H

The behavior of hydrogen in glow-discharge (GD) μc-Si:H has been characterized by ¹H NMR. The ¹H spectra consist of two components with different linewidths. The linewidth (FWHM) of the narrow component is about 0.5 kHz at ν₀ = 90 MHz, being much narrower than has been observed in GD a-Si:H deposited under a conventional low RF-power condition. It has been demonstrated that the 0.5-kHz FWHM component originates from the hydrogens in motional narrowing state, and such fast-moving hydrogens are incorporated both in μc-Si:H and high-power deposited a-Si:H.