Third-order optical nonlinearity in regioregular head-to-tail coupled poly(3-Hexylthiophene)

We measured the third-order optical nonlinearity of regioregular head-to-tail coupled poly (3-hexylthiophene) (HT-PHT) and regiorandom poly (3-hexylthiophene) (R-PHT) around exciton resonance using degenerate four wave mixing. The observed value of ∣χ⁽³⁾∣ at the exciton resonance peak of HT-PHT is in the order of 10^-9 esu which is approximately three-fold larger than that of R-PHT. We observed for the first time the enhancement in optical nonlinearity that occurs through the control of regularity of the polymeric structure. Response time of the nonlinearity was also measured using the transient grating method. The decay time of the transient grating in R-PHT and HT-PHT was less than 2 ps.     

Chemical modification of butyl rubber. II. Structure and properties of poly(ethylene oxide)-grafted butyl rubber

Poly(ethylene oxide)-grafted butyl rubbers (IIR-g-PEOs), which were synthesized from potassium salt of polyethylene glycol monomethyl ether (PEGM) and chlorinated butyl rubber, were found to behave like thermoplastic elastomers. The poly(ethylene oxide) (PEO) content of these amphiphilic polymers was ca. 10 wt %, and their PEO lengths were 750, 2000, and 5000, respectively. The grafted segments of PEO in butyl rubber (IIR) aggregated to form the PEO domains in IIR matrix. At constant PEO content, the longer the PEO segment length, the larger the size and the crystallinity of PEO domains became. This PEO domain worked as a cross-linking site and a reinforcing filler. The degree of swelling in water of IIR-g-PEO film that was prepared from PEGM-5000 was largest, but its emulsification ability was smallest among them. © 1995 John Wiley & Sons, Inc.     

Plasma Enhanced Chemical Vapor Deposition of Fluorinated Amorphous Carbon Thin Films from Tetrafluoroethylene and Tetraisocyanatesilane

Fluorinated amorphous carbon films were prepared from tetrafluoroethylene (TFE; C₂F₄) and tetraisocyanatesilane (TICS; Si(NCO)₄) using an RF plasma enhanced chemical vapor deposition method for the purpose of application to inter layer low permittivity films used in large scale integrated circuits. Structure of the deposited films was investigated by X-ray photoelectron spectroscopy and Fourier transform infrared spectroscopy. Adhesion characteristics were examined by a tape-peel method. Permittivity of the films was investigated from capacitance measurement on metal-insulator-semiconductor structure. The structural analysis revealed that the deposited films contained imide-like group in spite of the fact that TICS molecules contained isocyanate group . The films deposited under the flow ratio TICS/(TFE + TICS) = 70% showed permittivity of 2.3, good adhesion on silicon substrates, and higher thermal stability than the films deposited without TICS.     

New sterols from two edible mushrooms, Pleurotus eryngii and Panellus serotinus

Two edible mushrooms, Pleurotus eryngii and Panellus serotinus, have been investigated chemically. Two new sterols, 5alpha,9alpha-epidioxy-8alpha,14alpha-epoxy-(22E)-ergosta-6,22-dien-3beta-ol (1) and 3beta,5alpha-dihydroxyergost-7-en-6-one (2), have been isolated from P. eryngii, together with six known ones (3-8). Compound 1 was also isolated from P. serotinus. The structures of the new compounds were elucidated on the basis of their spectral data.     

TEMPO/NaBr/NaClO and NaBr/NaClO oxidations of cotton linters and ramie cellulose samples

Dried cotton linters and ramie cellulose samples were oxidized with 2,2,6,6-tetramethylpiperidine-1-oxyl (TEMPO)/NaBr/NaClO and NaBr/NaClO (i.e., TEMPO-free) in water at pH 10. The carboxy contents, degrees of polymerization (DPs), X-ray diffraction patterns, and solid-state ¹³C NMR spectra were measured or obtained for the oxidized products with and without subsequent NaBH₄ reduction. Cellulose nanofibrils were prepared from the oxidized cellulose samples by sonication in water and observed by atomic force microscopy and transmission electron microcopy. Because the cellulose molecules were depolymerized with NaBr/NaClO, the depolymerization behavior of the cellulose samples with TEMPO/NaBr/NaClO can be mainly explained by depolymerization with NaBr/NaClO (i.e., not TEMPO-related compounds or reactions). However, because C6-aldehydes formed in the disordered regions periodically present along the longitudinal direction of each cellulose microfibril, the viscosity-average DP values of the TEMPO/NaBr/NaClO-oxidized cellulose samples decreased to 200–300, while those with subsequent NaBH₄ reduction exhibited much higher DP values. The nanofibrils prepared from the TEMPO/NaBr/NaClO-oxidized cellulose samples had smallest fibril heights or widths of 5–6 nm. However, significant amounts of unfibrillated bundles with heights of 10–40 mm were present in the nanofibril/water dispersions. The high carboxy contents of the TEMPO/NaBr/NaClO-oxidized cellulose samples (1.62–1.63 mmol/g) indicated that significant amounts of carboxy groups were likely present in the disordered regions, probably forming tail-like polyglucuronate chains. Solid-state ¹³C NMR analysis revealed that some of the glucosyl units originally with the tg C6–OH conformation were transformed to other conformations by TEMPO/NaBr/NaClO oxidation, while the crystalline C4 signal areas remained constant.

Graphic abstract

     

The use of a highly sulfated cyclodextrin for the simultaneous chiral separation of amphetamine-type stimulants by capillary electrophoresis

We investigated the simultaneous chiral separation of nine amphetamine type stimulants (dl-norephedrine, dl-norpseudoephedrine, dl-ephedrine, dl-pseudoephedrine, dl-amphetamine, dl-methamphetamine, dl-methylenedioxyamphetamine (MDA), dl-methylenedioxymethamphetamine (MDMA), and dl-methylenedioxyethylamphetamine (MDEA)) by capillary electrophoresis using highly sulfated gamma-cyclodextrin (SU(XIII)-gamma-CD) as a chiral selector. Three different approaches using SU(XIII)-gamma-CD with 50 mM phosphate background electrolyte were designed; (I) high CD concentration (10 mM SU(XIII)-gamma-CD) at neutral pH (pH 7.0) in the normal polarity mode, (II) low CD concentration (1.0 mM) at low pH (pH 2.6) in the normal polarity mode and (III) high CD concentration at low pH (pH 2.6) in the reversed-polarity mode. In mode (II), the effects of adding three neutral CDs (beta-CD, dimethyl-beta-CD and hydroxypropyl-beta-CD) were also investigated. The best separation was obtained after optimizing mode (III) as follows: run buffer of 10 mM SU(XIII)-gamma-CD with 50 mM phosphate background electrolyte at pH 2.6, applied voltage of -12 kV and capillary temperature of 15 degrees C.     

An improved gravimetric method for determining oxygen in binary and ternary uranium oxides by addition of alkali or alkaline earth metal nitrate

A known amount of lithium or calcium nitrate solution is added to the sample powder which is then heated in air or oxygen. The oxygen in test samples of UO_2+x, Sr_0.1U_0.9O_{2 + x} and Sr_0.2U_0.5O_{2 + x} was determined with an estimated standard deviation of ± 0.002.     

Pretreatment with ammonia water for enzymatic hydrolysis of corn husk, bagasse, and switchgrass

Bagasse, corn husk, and switchgrass were pretreated with ammonia water to enhance enzymatic hydrolysis. The sample (2 g) was mixed with 1–6 mL ammonia water (25–28% ammonia) and autoclaved at 120°C for 20 min. After treatment, the product was vacuum-dried to remove ammonia gas. The dried solid could be used immediately in the enzymatic hydrolysis without washing. The enzymatic hydrolysis was effectively improved with more than 0.5 and 1 mL ammonia water/g for corn husk and bagasse, respectively. In bagasse, glucose, xylose, and xylobiose were the main products. The adsorption of CMCase and xylanase was related to the initial rate of enzymatic hydrolysis. In corn husks, arabinoxylan extracted by pretreatment was substantially unhydrolyzed because of the high ratio of arabinose to xylose (0.6). The carbohydrate yields from cellulose and hemicellulose were 72.9% and 82.4% in bagasse, and 86.2% and 91.9% in corn husk, respectively. The ammonia/water pretreatment also benefited from switchgrass (Miscanthus sinensis and Solidago altissima L.) hydrolysis.     

Dissolving metal reduction with crown ether — reductive decyanation

Toluene radical anion generated from potassium metal/dicyclohexano-18-crown-6/toluene system has been proved to be highly effective for reductive decyanation reaction of primary, secondary and tertiary cyanides.