Fluorinated poly(arylene ether ketone)s bearing pentafluorostyrene moieties prepared by a modified polycondensation

The polycondensation of decafluorobenzophenone with hexafluorobisphenol A was modified by the addition of a molecular sieve dehydrating apparatus to the refluxing reaction system. This modification promoted the polymerization and enabled the reactions to be conducted in milder conditions and completed in a shorter time, thereby depressing side reactions such as branching and crosslinking. The resulting fluorinated poly(arylene ether ketone)s (FPAEK) were free of gel particles and possessed the designed molecular weights. This modified procedure was also suitable for introducing crosslinkable pentafluorostyrene (FSt) moieties into the polymers at the chain ends and/or inside the chain with the vinyl group of FSt being pendant. The resulting FSt containing fluorinated poly(arylene ether ketone)s (FPAEK‐FSt) can then be thermally crosslinked at 100 °C in the presence of 1% benzoyl peroxide (BPO) or at 250 °C without any initiator. The glass‐transition temperatures (T_g's) of FPAEK increased with increasing molecular weight and leveled off at about 147 °C for the polymer with a number‐average molecular weight of 18,600 Da, whereas the values were not apparently affected by the addition of FSt units. However, crosslinking of the FPAEK‐FSt resulted in an approximate 30 °C increase of the T_g. Spin‐coating FPAEK‐FSt onto silicon wafers followed by crosslinking gave films with excellent thermal stability, physical strength, and adhesion to the substrate as well as good reproducibility in terms of film preparation and optical properties. The refractive index and birefringence of the films measured at a wavelength of 1.55 μm were 1.502 and 2.5 × 10^?3, respectively. © 2002 Government of Canada. Exclusive worldwide publication rights in the article have been transferred to Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 40: 4205–4216, 2002     

K-Pb-Tl-O复合氧化物的合成和电子结构的XPS研究

用熔盐阳极电沉积法合成了导电的复合氧化物K-Pb-Tl-O晶体.这些晶体具有纳米尺寸层状结构.用XPS对其进行了表征,并与相关的化合物进行了比较.实验表明,氧化物中的Pb和Tl都以高价态的单一价态存在,但电子结合能比相应的非导电低价化合物的低.该文用原子外弛豫效应解释了复合氧化物中的Pb和Tl的结合能的反常现象.讨论了它们的价电子结构与导电性的关系.     

Preparations of ginsenoside Rg1 immunogen and125I-labeled antiğen

This work began with the side chain of ginsenoside Rg₁ which was acetylized with Ac₂O-Pyr and oxidized by OsO₄ and NaIO₄ to give ginsenoside Rg₁ aldehyde(2), which was further converted into an unsaturated ester(3) by Wittig-Horner reaction. The unsaturated ester(3) was treated with N₂H₄ and HNO₂ to yield Rg₁ azide(4) which was directly conjugated with BSA to give immunogen: ginsenoside Rg₁-BSA conjugate(5). This azide(4) was conjugated with tyramine to give ginsenoside Rg₁-tyramine conjugate which was labelled with free Na¹²⁵I by CH-T to yield¹²⁵I-labeled antigen: gensenoside Rg₁-¹²⁵I-tyramine(6). The labelling rate was 40%–50% and specific activity was 3.0–4.0 MBq/g.     

Thermal degradation and flame retardancy of flexible polyvinyl chloride containing solid superacid

The objective of the present article was to study the thermal degradation behavior and flame retardancy of flexible polyvinyl chloride (PVC) composites containing TiO₂/SO ^2?₄ solid superacid because of its strong catalytic ability for esterification and dehydration. The TiO₂/SO ^2?₄ solid superacid was synthesized by using precipitation immersion method, and its structure was investigated by X-ray diffraction. As expected, the value of limiting oxygen index for PVC/Sb₂O₃/(TiO₂/SO ^2?₄ ) composite was 32.5% and the char yield of PVC/Sb₂O₃/(TiO₂/SO ^2?₄ ) composite was significantly improved compared to neat PVC in thermogravimetry tests. In addition, the peak heat release rate and smoke production rate of PVC/Sb₂O₃/(TiO₂/SO ^2?₄ ) decreased by 14% and 42%, respectively, compared with neat PVC. Moreover, the results of cone calorimetry tests and electron micrograph of char residue showed that the char yield of TiO₂/SO ^2?₄ was enhanced, resulting in a strong char layer structure with outstanding fire retardance cone. In conclusion, the results of this work showed that the addition of solid superacid promoted the decomposition and dehydration of PVC, which formed a compact and continuous char layer on the surface of the material. Hence, the study provides a new perspective for producing composites with excellent flame retardancy and smoke suppression properties of PVC.

     

Novel 1,3,5-thiadiazine-2-thione derivatives containing a hydrazide moiety: Design,synthesis and bioactive evaluation against phytopathogenic fungi in vitro and in vivo

A series of novel 1,3,5-thiadiazine-2-thione derivatives bearing a hydrazide moiety were designed, synthesized and evaluated for their biological activities against phytopathogenic fungi. The antifungal bioassays indicated that the title compound 5b impressively displayed the obvious selectivity and specificity aganist Rhizoctonia solani (Rs) in vitro and in vivo. The above researches provide a significant reference for the further structural optimization of 1,3,5-thiadiazine-2-thione derivatives bearing a hydrazide moiety as potential fungicides.     

微波辅助快速制备2D/1D ZnIn2S4/TiO2 S型异质结及其光催化制氢性能

The threat and global concern of energy crises have significantly increased over the last two decades. Because solar light and water are abundant on earth, photocatalytic hydrogen evolution through water splitting has been considered as a promising route to produce green energy. Therefore, semiconductor photocatalysts play a key role in transforming sunlight and water to hydrogen energy. To date, various photocatalysts have been studied. Among them, TiO₂ has been extensively investigated because of its non-toxicity, high chemical stability, controllable morphology, and high photocatalytic activity. In particular, 1D TiO₂ nanofibers (NFs) have attracted increasing attention as effective photocatalysts because of their unique 1D electron transfer pathway, high adsorption capacity, and high photoinduced electron–hole pair transfer capability. However, TiO₂ NFs are considered as an inefficient photocatalyst for the hydrogen evolution reaction (HER) because of their disadvantages such as a large band gap (~3.2 eV) and fast recombination of photoinduced electron–hole pairs. Therefore, the development of a high-performance TiO₂ NF photocatalyst is required for efficient solar light conversion. In recent years, several strategies have been explored to improve the photocatalytic activity of TiO₂ NFs, including coupling with narrow-bandgap semiconductors (such as ZnIn₂S₄). Recently, microwave (MW)-assisted synthesis has been considered as an important strategy for the preparation of photocatalyst semiconductors because of its low cost, environment-friendliness, simplicity, and high reaction rate. Herein, to overcome the above-mentioned limiting properties of TiO₂ NFs, we report a 2D/1D ZnIn₂S₄/TiO₂ S-scheme heterojunction synthesized through a microwave (MW)-assisted process. Herein, the 2D/1D ZnIn₂S₄/TiO₂ S-scheme heterojunction was constructed rapidly by using in situ 2D ZnIn₂S₄nanosheets decorated on 1D TiO₂ NFs. The loading of ZnIn₂S₄ nanoplates on the TiO₂ NFs could be easily controlled by adjusting the molar ratios of ZnIn₂S₄ precursors to TiO₂ NFs. The photocatalytic activity of the as-prepared samples for water splitting under simulated solar light irradiation was assessed. The experimental results showed that the photocatalytic performance of the ZnIn₂S₄/TiO₂ composites was significantly improved, and the obtained ZnIn₂S₄/TiO₂ composites showed increased optical absorption. Under optimal conditions, the highest HER rate of the ZT-0.5 (molar ratio of ZnIn₂S₄/TiO₂= 0.5) sample was 8774 μmol·g^-1·h^-1, which is considerably higher than those of pure TiO₂ NFs (3312 μmol·g^-1·h^-1) and ZnIn₂S₄nanoplates (3114 μmol·g^-1·h^-1) by factors of 2.7 and 2.8, respectively. Based on the experimental data and Mott-Schottky analysis, a possible mechanism for the formation of the S-scheme heterojunction between ZnIn₂S₄ and TiO₂ was proposed to interpret the enhanced HER activity of the ZnIn₂S₄/TiO₂heterojunctionphotocatalysts.      

Synthesis of 4″-benzyloxyimino-4″-deoxyavermectin Bla derivatives

Six new 4″-benzyloxyimino-4″-deoxyavermectin Bla derivatives were synthesized from avermectin Bla by the selective protection of C-5-hydroxy group,oxidation of C-4″-hydroxy group,and deprotection followed by reaction with O-substituted hydroxylamine hydrochlorides.Their structures were confirmed by IR,~1H NMR,~(13)C NMR and MS.Insecticidal activities of the derivatives against Phopalosiphum pseudobrassicae,Spodoptera exigua and Pluteua xylosteua were evaluated.     

Catalytic Adsorptive Stripping Voltammetry of Germanium(IV) in the Presence of Gallic Acid and Vanadium(IV)‐EDTA

A highly sensitive and selective catalytic adsorptive cathodic striping procedure for the determination of trace germanium is presented. The method is based on adsorptive accumulation of the Ge(IV)‐gallic acid (GA) complex onto a hanging mercury drop electrode, followed by reduction of the adsorbed species. The reduction current is enhanced catalytically by addition of vanadium(IV)‐EDTA. The optimal experimental conditions include the use of 0.03 mol/L HClO₄ (pH1.6), 6.0×10^?3 mol/L GA, 3.0×10^?3 mol/L V(IV), 4.0×10^?3 mol/L EDTA, an accumulation potential of ?0.10 V(vs. Ag/AgCl), an accumulation time of 120 s and a differential pulse potential scan mode. The peak current is proportional to the concentration of Ge(IV) over the range of 3.0×10^?11 to 1.0×10^?8 mol/L and the detection limit is 2×10^?11 mol/L for a 120 s adsorption time. The relative standard deviation at 5.0×10^?10 mol/L level is 3.1%. No serious interferences were found. The method was applied to the determination of germanium in ore, mineral water and vegetable samples with satisfactory results.     

Preparation and characterization O-lauroyl chitosan/poly (L-lactic acid) blend membranes by solution-casting approach

O-Lauroyl chitosan/poly(L-lactide) (OCS/PLLA) blend membranes with different compositions were prepared by solution-casting approach using chloroform as common solvent. The experimental results of FT-IR, DSC and WAXD indicated that inter-association hydrogen-bond interactions existed between OCS and PLLA in the blend membranes. And SEM observation confirmed that the blend membranes with suitable compositions were compatible.     

Heat shock protein 27 interacts with vimentin and prevents insolubilization of vimentin subunits induced by cadmium

Vimentin is an intermediate filament that regulates cell attachment and subcellular organization. In this study, vimentin filaments were morphologically altered, and its soluble subunits were rapidly reduced via cadmium chloride treatment. Cadmium chloride stimulated three major mitogen-activated protein kinases (MAPKs): extracellular signal-regulated kinase (ERK), c-Jun N-terminal kinase (JNK), and p38, and led apoptotic pathway via caspase-9 and caspase-3 activations. In order to determine whether MAPKs were involved in this cadmium-induced soluble vimentin disappearance, we applied MAPK-specific inhibitors (PD98059, SP600125, SB203580). These inhibitors did not abolish the cadmium-induced soluble vimentin disappearance. Caspase and proteosome degradation pathway were also not involved in soluble vimentin disappearance. When we observed vimentin levels in soluble and insoluble fractions, soluble vimentin subunits shifted to an insoluble fraction. As we discovered that heat-shock protein 27 (HSP27) was colocalized and physically associated with vimentin in unstressed cells, the roles of HSP27 with regard to vimentin were assessed. HSP27-overexpressing cells prevented morphological alterations of the vimentin filaments, as well as reductions of soluble vimentin, in the cadmium-treated cells. Moreover, HSP27 antisense oligonucleotide augmented these cadmium-induced changes in vimentin. These findings indicate that HSP27 prevents disruption of the vimentin intermediate filament networks and soluble vimentin disappearance, by virtue of its physical interaction with vimentin in cadmium-treated SK-N-SH cells.