Synthesis of poly(diallyl phthalate) and silica gel polymer hybrids utilizing π–π interactions

We report here the synthesis of homogeneous polymer hybrids of poly(diallyl phthalate) (PDAP) and silica by utilizing π–π interactions. Use of arylalkoxysilanes such as phenyltrimethoxysilane (PhTMOS), phenethyltrimethoxysilane (PhenethylTMOS) and mesityltrimethoxysilane (MesTMOS) as sources for inorganic phases resulted in optically transparent PDAP-silica polymer hybrids in a wide range of organic and inorganic content ratios. On the other hand, alkoxysilanes such as tetramethoxysilane (TMOS), methyltrimethoxysilane (MTMOS) and i-butyltrimethoxysilane (iBuTMOS) resulted in phase separated, turbid solids. A mixture of tetramethoxysilane (TMOS) and PhTMOS was also studied for the synthesis of PDAP-silica gel polymer hybrids to control the cross-linking density in the inorganic phase. Homogeneity was found to be improved with an increase in PhTMOS content. These homogeneous PDAP polymer hybrids were found to have high thermal stability which wasachieved by nano-scale dispersion of PDAP in silica through extensiveinterface interactions. The homogeneity of the polymer hybrids was confirmed by SEM and TEM, which demonstrate a nanometer level integration of the organic polymer and the inorganic phase.     

Intramolecular oxyselenenylation and deselenenylation reactions in water, conducted by employing polymer-supported arylselenenyl bromide

After immobilizing arylselenenyl bromide on polymer resin, the oxyselenenylation reaction of olefin was carried out in water. An amphiphilic polymer-supported arylselenenyl bromide was employed, and various intramolecular oxyselenenylation and deselenenylation reactions proceeded smoothly in water in fair chemical yields (up to an 83% yield).     

15β-Hydroxylation of Lithocholic Acid by cunninghamella sp.

The microbiological transformation of lithocholic acid (3α-hydroxy-5β-cholanic acid) into 3α, 15β-dihydroxy-5β-cholanic acid by Cunninghamella sp. is Investigated. The structure has been determined on the basis of two-dimensional ¹H-NMR.     

pH-regulated formation of amyloid-like beta-sheet assemblies from polyglutamate grafted polyallylamine

A novel artificial protein with simple primary structure, poly(gamma-methyl-L-glutamate)-grafted polyallylamine, has been prepared and the resultant peptide has shown a unique property of pH-regulated conformation and morphology.     

An application of silaned glass beads to the preconcentration and spectrophotometric determination of traces of phosphorus with molybdate

Silaned glass beads are applied to the preconcentration and spectrophotometric determination of phosphorus as the phosphomolybdenum blue complex. Traces of phosphorus in water are collected as a phosphomolybdenum blue complex on a column of the beads. The phosphomolybdenum blue is eluted with N,N-dimethylformamide and the absorbance of the eluate continuously monitored at 700 nm. The height of the very sharp peak obtained is proportional to the amount of phosphorus present and 0.1-0.5 mug of phosphorus in a 10-ml sample can be determined reproducibly. Interference from arsenate is eliminated by addition of a reducing agent. High concentrations of silica cause a small positive error. This method is applicable to the analysis of river water and sea-water samples.     

Effect of phenyl substituent on the dimerization of copper(II)-carboxylate in solvent extraction of copper(II) with phenylacetic acid

The effects of the phenyl substituent on the dimerization of copper(II) carboxylate in the solvent extraction of copper(II) with phenylacetic acid using benzene and 1-octanol as a solvent were investigated, at 25 degrees and at the aqueous ionic strength of 0.1M (NaClO(4)). The dimerization of copper(II) phenylacetate has been found to be written as: 2CuA(2)Cu(2)A(4) in 1-octanol, and 2CuA(2)(HA)(2)Cu(2)A(4)(HA)(2) + (HA)(2) in benzene, with the dimerization constants, log K = 2.24 and log K = 4.19, respectively. It was proved that the phenyl group inhibits the formation of the dimeric copper(II) phenylacetate, and its effect is partially shielded by a methylene substituent.     

Determination of a polymeric hindered amine light stabilizer in polypropylene formulated with magnesium hydroxide flame retardant by reactive thermal desorption-gas chromatography.

A polymeric hindered amine light stabilizer (HALS), Tinuvin 622 (MW [symbol: see text] 4000), in PP materials formulated with a magnesium hydroxide flame retardant was determined by reactive thermal desorption (RTD) gas chromatography (GC). Two kinds of the HALS components that were formed through the RTD in the presence of tetramethylammonium hydroxide [(CH3)4NOH, TMAH] were clearly observed in the chromatograms of the PP samples, with negligible interference from the other additives and the PP substrate. Here, the coexisting flame retardant was proved to affect significantly the RTD process of the occluded HALS. As a result, the recovery of the HALS components in the RTD-GC chromatograms of the PP samples increased with increase in the content of the flame retardant. This enhancement of the HALS recovery is attributed mainly to the preferential exposure of the HALS on the surface of the ground PP sample through the interaction between the polymeric HALS and the flame retardant in the molten PP during kneading. In spite of such a considerable action of the flame retardant, the observed intensities of the characteristic peaks of HALS by RTD-GC showed a good linear relationship with the HALS content in the PP samples with constant content of the flame retardant (50 phr); this relationship could be used as the calibration line for the determination of the polymeric HALS in the PP materials containing the flame retardant.     

Photoluminescence enhancement of PEG-modified YAG:Ce3+ nanocrystal phosphor prepared by glycothermal method

Y3Al5O12:Ce3+ (YAG:Ce3+) nanocrystals were synthesized in 1,4-butylene glycol (BG) with and without poly(ethylene glycol) (PEG) by the glycothermal method. The internal quantum efficiency of the photoluminescence (PL) corresponding to the 5d --> 4f transition of Ce3+ in the YAG:Ce3+ nanocrystal increased from 21.3 to 37.9% by addition of PEG, while no appreciable change in the primary particle size, the crystallite size, and the lattice distortion was recognized by transmission electron microscopy and X-ray diffractometry. The thermogravimetry-differential thermal analysis, Fourier transform infrared absorption spectroscopy and 1H --> 13C cross-polarization magic angle spinning nuclear magnetic resonance (CP-MAS NMR) confirmed the preferential coordination of PEG to the YAG:Ce3+ nanocrystal. 27Al single-pulse excitation MAS NMR reveals that the ratio of the 4-fold coordination site to the 6-fold coordination site increased from 0.53 to 0.72 by addition of PEG. We conclude that the surface modification of the YAG:Ce3+ nanocrystal by PEG induces the surface passivation, the prevention of the oxidation of Ce3+ to Ce4+, the promotion of the incorporation of Ce3+ into YAG and the local structural rearrangement, resulting in the PL enhancement.     

Rhodium-catalyzed isomerization of alpha-arylpropargyl alcohols to indanones: involvement of an unexpected reaction cascade

A rhodium-catalyzed isomerization of alpha-arylpropargyl alcohols to indanones has been developed under mild conditions. Considering the ease of preparation of these propargyl alcohols (terminal alkynes + aromatic aldehydes), this method provides a new way of constructing indanones with high efficiency. By the mechanistic investigations using deuterium-labeled substrates, it has also been demonstrated that the reaction goes through an unexpected cascade, with a 1,4-hydrogen shift being the turnover-limiting step of the catalytic cycle.