UV-induced photoisomerization of acetylacetone in low-temperature argon matrixes has been studied by Fourier transform infrared spectroscopy. Identifications of the species produced by UV irradiation (λ > 280 nm) were carried out with the aid of the density functional theory (DFT) calculation, in which the 6-31G* basis set was used to optimize the geometrical structures. By comparison of the observed infrared bands with the calculated spectral patterns, it was found that cis−trans isomerization around the C−C, CC, and C−O bonds occurs to produce less-stable enol isomers, 2-hydroxy-2-penten-4-one. Shorter-wavelength irradiation (λ < 280 nm) induced hydrogen-atom migration of the enol isomers to produce a keto isomer, 2,4-pentanedione.

UV-induced conformational changes among chelated and nonchelated enol isomers of (trifluoroacetyl)acetone in a low-temperature argon matrix were investigated by Fourier transform infrared spectroscopy. An infrared spectrum measured after deposition before UV irradiation was assigned to a chelated enol isomer, 1,1,1trifluoro-4-hydroxy-3-penten-2-one, where no bands for the other chelated enol isomer, 5,5,5-trifluoro-4hydroxy-3-penten-2-one, were found, the latter being formed from the former by moving of the hydrogen atom in the O-H group to the CdO group. Conformations of 3 nonchelated enol isomers among 14 were determined by a comparison of the infrared spectra measured after UV irradiation with the spectral patterns obtained by the density functional theory calculations at the DFT/B3LYP/6-31G* level. This selective isomerization was explained in terms of the inhibition of internal rotation in vibrational relaxation of photoexcited species, which was proposed in our previous studies of acetylacetone and hexafluoroacetylacetone. An infrared spectrum of a transient photoproduct was measured while the matrix sample was continuously exposed to the UV light. It was identified as another nonchelated enol isomer.

No abstract

: The wool fabrics were treated by pulse corona discharge, followed by a keratinase to obtain shrink-proofed wool fabrics. The effects of the dual treatment on surface modification and dyeability for three kinds of leveling acid dyes with one, two, or three sulfonate groups in the structure were investigated. Although the physical surface was almost unchanged by the pulse corona discharge judging from the SEM observation, the ESCA analyses showed that the components of C and S atoms were greatly changed by the discharge. From the surface chemical composition, it is likely that the lipid layer of wool was partly removed and the remaining one on the surface was oxidized to give -C-O-, -C=O and -COO-residues. Furthermore, the presence of cystine monoxide (-SO-S-), cystine dioxide (-SO2-S-), and cysteic acid (-SO3 − ) was confirmed after the discharge. The dyeing rate was increased considerably by the pulse corona discharge/enzyme treatment, but the equilibrium dye uptake was unchanged. The sorption isotherms obtained were analyzed using dual sorption mechanism consisted of the Langmuir and partition type sorption, and three sorption parameters, which are the number of binding site, S , the intrinsic binding constant for the Langmuir type sorption, KL, and the partition coefficient, KP are discussed.

SYNOPSISAqueous NMMO solutions containing NMMO above 50% are good solvents for syndiotacticity-rich poly(viny1 alcohol) (s-PVA). Although water is not a good solvent and dissolves s-PVA at temperatures above 100°C, the mixtures dissolve it at temperatures below 100°C. s-PVA fibers were prepared through gel-spinning of s-PVA/NMMO/water (NMMO : water = 70 : 30) mixtures in cold water and wet-spinning of the solution in methanol. The mechanical properties and fine structure of the drawn fibers were examined based on the results of measurements of tensile properties, thermal properties, birefringence, and optical and electron microscopic observations. The strength and Young's modulus of the drawn fibers were approximately to 2.0 and 45 GPa, respectively. The reason why the fibers with theoretical mechanical properties could not be prepared was surmised to be related to the structure of the amorphous regions.

: To clarify the dyeability of shrink-proofed wool fabrics treated with permonosulfate (PMS) and a keratinase, the sorption behaviors of four kinds of leveling acid dyes containing mono-, di-, and tri-sulfonate groups were investigated. The dyeing rate and sorption isotherms were determined to elucidate the effects of the dye structure and the treatment of wool fibers. The dyeing rate was discussed using apparent diffusion coefficients. The sorption isotherms were analyzed using dual sorption mechanism to calculate the sorption parameters, the number of binding sites S , the intrinsic binding constant KL, and the partition coefficient KP. As a result, the dyeing rate and the equilibrium dye uptake for the fibers treated with PMS alone were much smaller than those of the untreated ones. The dyeing rate and the equilibrium dye uptake were restored by the subsequent treatment with the enzyme. The S and KL values were also decreased by the oxidation with PMS. On the other hand, the ESCA and FT-IR spectra showed the presence of cystine monoxide (-SO-S-), cystine dioxide (-SO2-S-), and cysteic acid (-SO3 -) after the treatment with PMS. The observations obtained for the dyeing behaviors can be explained in the presence of cysteic acid generated in the fibers after the PMS treatment. It is likely that the decrease of dye uptake and S is due to the neutralization between the cysteic acid introduced by the oxidation and the protonated amino groups in the fibers that work as the binding sites for the dye anions. This tendency appeared strongly for the tri-sulfonate dye compared to the mono-sulfonate dye.

No abstract

Aqueous NMMO solutions containing NMMO above 50% are good solvents for syndiotacticity‐rich poly(vinyl alcohol) (s‐PVA). Although water is not a good solvent and dissolves s‐PVA at temperatures above 100°C, the mixtures dissolve it at temperatures below 100°C. s‐PVA fibers were prepared through gel‐spinning of s‐PVA/NMMO/water (NMMO: water = 70 : 30) mixtures in cold water and wet‐spinning of the solution in methanol. The mechanical properties and fine structure of the drawn fibers were examined based on the results of measurements of tensile properties, thermal properties, birefringence, and optical and electron microscopic observations. The strength and Young's modulus of the drawn fibers were approximately to 2.0 and 45 GPa, respectively. The reason why the fibers with theoretical mechanical properties could not be prepared was surmised to be related to the structure of the amorphous regions. © 1993 John Wiley & Sons, Inc.