天然树脂局部结构的径向分布函数研究

本工作用x射线衍射技术分析计算了二种天然树脂的局部结构参数,由测得的衍射强度数据求出了它们的结构因子I(r)和径向分布函数RDF(r),并由此得到了分子链内临近原子和次临近原子平均间距、配位数和短程有序畴。     

Studies on the chemical constituents of the South China Sea sponge Phacellia fusca

Three pyrrololactam alkaloids have been isolated from the marine sponge Phacellia fusca Schmidt collected from the South China Sea, and their structures were determined as 1–3 , on the grounds of spectral data. This is the first report of these compounds from this sponge. The structure of 1 was confirmed by X-ray analysis.     

Interaction of glucose oxidase with alkyl-substituted sepharose 4B

Glucose oxidase (GOD) is often used in immobilized forms for determination of glucose. To examine the possibility of its adsorption by hydrophobic interactions, palmityl-substituted Sepharose 4B (Sepharoselipid) was employed as an adsorptive matrix. Various conditions were used in tests to improve the limited immobilization of the enzyme observed under normal (native) conditions, including use of high concentrations of denaturing agents. Of the denaturants used, only the cationic detergent dodecyl trimethyl ammonium bromide was effective in denaturing the protein and exposing its hydrophobic sites for interaction with alkyl residues on the support. This, followed by the process of renaturation, provided catalytically active immobilized preparations. The apoenzyme, prepared by treatment of the holoenzyme with acidified (NH4)2SO4 or thermal denaturation, was totally immobilized on the support. Furthermore, it was shown that either flavin adenine dinucleotide (FAD) or the alkyl residues, not both, may interact with the nucleotide site at any given time. Results are discussed in terms of high rigidity of GOD molecule and limited exposure of hydrophobic sites in its native structure. The observations are in accord with suggestions in the literature that the FAD pocket is a very narrow channel of hydrophobic properties, adapted to accept its natural coenzyme.     

“Living” radical graft polymerization of styrene to styrene butadiene rubber (SBR) with 2,2,6,6‐tetramethyl‐1‐piperidinyloxy (TEMPO)

Well‐defined graft copolymers with styrene butadiene rubber (SBR) backbones and polystyrene branches were synthesized by living free radical polymerization (LFRP) techniques. Thus 1‐ benzoyl‐2‐phenyl‐2‐(2′,2′,6′,6′‐tetramethyl‐piperidinyl‐1′‐oxy)ethane (BZ‐TEMPO) was synthesized and hydrolyzed to the corresponding 1‐hydroxyl derivative. This functional nitroxyl compound was coupled with brominated SBR (SBR‐Br). The resulting macroinitiator (SBR‐TEMPO) for “living” free radical polymerization was then heated in the presence of styrene for the formation of the controlled graft copolymer. ¹H‐NMR and IR spectroscopy were used to investigate the structure of the polymers. Copyright © 2004 John Wiley & Sons, Ltd.     

Nitroxide mediated living radical polymerization of styrene onto poly (vinyl chloride)

Nitroxide‐mediated ‘living’ free radical polymerisation (LREP) was employed for the first time to prepare graft copolymer by having arylated poly (vinyl chloride) (PVC‐Ph) as a backbone and polystyrene (PS) as branches. The graft copolymerization of styrene was initiated by arylated PVC carrying 2,2,6,6‐tetramethyl‐1‐piperidinyloxy (TEMPO) groups as a macroinitiator. Thus, the arylated PVC was prepared in the mild conditions and these reaction conditions could overcome the problem of gelation and crosslinking in polymers. Then, 1‐hydroxy TEMPO was synthesized by the reduction of TEMPO with sodium ascorbate. This functional nitroxyl compound was coupled with brominated arylated PVC (PVC‐Ph‐Br). The resulting macro‐initiator (PVC‐Ph‐TEMPO) for ‘living’ free radical polymerization was then heated in the presence of styrene to form graft copolymer. DSC, GPC, ¹HNMR, and FT‐IR spectroscopy were employed to investigate the structure of the polymers. Copyright © 2007 John Wiley & Sons, Ltd.     

Synthesis and structural characterisation of a novel tris-methylene bridged compound (NO) 4Fe2 Se(μ-CH2)3

The tris-methylene bridged compound (NO)₄Fe₂Se(μ-CH₂)₃ has been isolated. It has been characterised by IR and ¹H, ¹³C, and ⁷⁷Se NMR spectroscopy. Its structure has been determined by single-crystal X-ray diffraction methods. The structure consists of a heavy atom triangle consisting of one Se and two Fe atoms. The Fe-Fe and the two Fe-Se edges are bridged by methylene groups.     

Syntheses, characterization and study of the use of cobalt (II) Schiff-base complexes as catalysts for the oxidation of styrene by molecular oxygen

Schiff-Base complexes of bis-5-phenylazosalicylaldehyde ethylenediimine and bis-5-phenylazosalicylaldehyde-O-phenylenediimine ligands with Co(II) (I and II) have been synthesized and characterized by their IR spectra and elemental analyses. These complexes catalyze the oxidation of styrene in the presence of dioxygen and excess pyridine. The effect of the reaction conditions on the oxidation of styrene was studied by varying solvent, nature and amount of the catalyst and substrate. The catalytic behavior of the studied complexes was shown to be dependent on the conditions applied. In all reactions, acetophenone and 1- phenylethanol were the only observed products.     

Determination of percolation threshold electroactivity and phase behavior study on conducting blends of thermotropic polyesters and polyaniline

The new thermotropic polyester/polyaniline (PIn/PAni) blends have been prepared by solution blend of synthesized liquid crystalline poly[4,4′‐bis (ω‐alkoxy) biphenylisophthalate]s having four and six methylene units in spacer (PI4 and PI6) with PAni doped with camphorsolfonic acid (CSA). The percolation threshold electroactivity of prepared blend films has been determined by cyclic voltammetry. The effect of the PAni concentration, solvent nature and polyester structure on the electroactivity of the blends has been investigated. The extremely low percolation threshold of prepared PIn/PAni‐CSA blends from dimethylformamide (DMF) and m‐cresol solution was 3% weight of PAni‐CSA. The amount of conducting polymer necessary to retard the formation of the liquid crystalline (LC) phase is up to 45% by weight. Phase behavior studies by differential scanning calorimetry and polarizing microscopy show that blends with 45% of conducting polymer are both liquid crystal and conductive. The morphology of the blends has been investigated by scanning electron microscopy. Copyright © 2004 John Wiley & Sons, Ltd.