Blue light-emitting polyfluorenes containing dibenzothiophene-S,S-dioxide unit in alkyl side chain

Blue light-emitting polyfluorenes containing dibenzothiophene-S,S-dioxide(SO) unit in alkyl side chain(PF-FSOs and PF-CzSOs) were synthesized. All the polymers show high thermal stability with the decomposition temperatures over400 °C. The highest occupied molecular orbital(HOMO) and the lowest unoccupied molecular orbital(LUMO) energy levels of the copolymer slightly decrease with the increase of SO content in side chain. PL spectra of the polymers show slightly red shift and broadening with the increase of solvent polarities, indicating unremarkable intramolecular charge transfer(ICT) effect in the polymers containing SO unit in alkyl side chain. EL spectra of the polymers are almost unchanged in the current densities from 100 to 400 mA cm.2, indicating the superb EL stability of the resulted polymers. The EL spectra of the copolymers exhibit obvious blue-shift and narrowing with the CIE of(0.18, 0.11) for PF-FSO10 and(0.17, 0.11) for PF-CzSO10, respectively,compared with PF-SO10 containing SO unit in main chain with the CIE of(0.16, 0.17) and PFO with the CIE of(0.18, 0.18).The superior device performances were obtained with the luminous efficiency(LEmax) of 1.17 and 0.68 cd A.1 for PF-FSO15 and PF-CzSO20, respectively, compared with the LEmax of 0.37 cd A.1 for PFO. The results indicate that linking SO unit to alkyl side chain of the polyfluorene is a promising strategy for efficient blue light-emitting polymers.     

Sorption characteristics and mechanisms of organic contaminant to carbonaceous biosorbents in aqueous solution

A series of carbonaceous biosorbents was prepared by pyrolyzing pine needles,a model biomass,at various temperatures (100-700℃) under an oxygen-limited condition for 6h. The elemental composi-tions and the specific surface areas (BET-N2) of the biosorbents were analyzed. Sorption properties of 4-nitrotoluene to the biosorbents and their mechanisms were investigated,and then correlated with the structures of the biosorbents. The result shows that with the increase of the pyrolytic temperature,the aromaticity of the carbonaceous biosorbents increases dramatically and the polarity (the (N O)/C atomic ratio) decreases sharply. Correspondingly,conformations of the organic matter in the biosor-bents transform gradually from a "soft-state" to a "hard-state" and the specific surface areas of the resultant biosorbents extend rapidly. The sorption isotherms fit well with the Freundlich equation. The regression parameters (i.e.,N and lgKf) are linearly related to the aromaticity indices (the H/C atomic ratio). Contributions of adsorption and partition to total sorption of the carbonaceous biosorbents are quantified. The adsorption of the carbonaceous biosorbents increases quickly with the increase of the pyrolytic temperature. The saturated adsorption amounts (Qmax) increase linearly with the increase of the specific surface areas (SA) of the biosorbents. For the carbonaceous biosorbents with hard-state carbon,the calculated normalized-Qmax values by SA are comparable to the theoretical estimation (2.45 μmol/m2). In comparison,for the carbonaceous sorbents with soft-state carbon,the calculated nor-malized-Qmax values by SA are much higher than the theoretical estimation. The partition coefficients (Kom) increase with the decrease of the polarity of the biosorbents,reaching a maximum,and then de-crease sharply with further decreasing the polarity,suggesting that partition mechanism be dominated by the compatibility and accessibility of the sorbent medium with organic pollutant. These observations will provide a theoretical and practical reference to design a cost-effective and high-efficient sorbent,and to accurately predict sorption properties and mechanisms of a given sorbent.     

TRANSESTERIFICATION OF POLY（BISPHENOL A CARBONATE） WITH AROMATIC AND ALIPHATIC SEGMENTS IN BUTYLENE TEREPHTHALATE-CAPROLACTONE COPOLYESTER

In this article, the transesterification of poly(bisphenol A carbonate) (PC) with butylene terephthalate-caprolactone copolyester at a weight ratio 50/50 (BCL(21)) was thoroughly investigated by proton nuclear magnetic resonance spectroscopy (^1H-NMR), in conjunction with a model compound. The ^1H-NMR results of the annealed blend PC/BCL(21) show that the formation of bisphenol A-terephthalate ester units is the same as in the annealed blend of PC with PBT, and the transesterification actually occurs between PC and butylene terephthalate (BT) segments in BCL(21). By comparison with the model compound bisphenol A dibutyrate, the new signal appearing at δ=2.56 in the ^1H-NMR spectrum confirms the existence of bisphenol A caprolactone ester units resulting from the exchange reaction of PC with caprolactone (CL) segments. ^1H-NMR analysis of the transesterification rates reveals that the reaction of PC with aromatic and aliphatic segments in BCL(21) proceeds in a random manner. The miscibility of the blend PC/BCL(21) copolyester is favorable for the transesterification of PC with BT segments and CL segments.     

Catalytical Activities of Reconstructed Hemoglobin with Different Central Ions in Prosthetic Group

Hemoglobin(Hb) was de-prosthetized, which was then reconstructed with the prosthetic groups with different central metal ions including Fe ( Ⅱ ), Co ( Ⅰ ) and Mn( Ⅰ ). The spectral properties along with the catalase and peroxidase activities of the reconstructed hemoglobin were compared with those of Hb and prosthetic groups with different ions. When the central ion is iron, the reconstituted Hb(rHb) has the highest catalase and peroxidase activities. Maybe it is the reason that iron is chosen as the central ion in the prosthetic groups of natural hemoproteins. Different from peroxidase activity, the catalase activity of hemin cannot be enhanced by the microenvironment of apoHb. This result shows that the structure of apoHb is more similar to that of aooHRP than that of apocatalase.     

SYNTHESIS AND CHARACTERIZATION OF LIQUID CRYSTAL POLYESTERS WITH T-SHAPED TWO-DIMENSIONAL MESOGENIC UNITS(Ⅲ)*

A new series of liquid crystal polyesters with T-shaped two-dimensional mesogenic units weresynthesized by melt polycondensation of the diacetates of 2-(4'-alkoxy -phenyl)-hydroquinones with 4,4'-alkylenedioxydibenzoic acid. The polymers were characterized by using polarized microscopy, DSC and X-ray diffraction. It was realized that all the polymers have nematic thermotropic liquid crystallinecharacteristics. The melting temperature (T_m) and isotropization temperature (T_i) of the polymers changeregularly with varying lengths of the alkoxy side group and the length of the alkylene group in the main chainin company with an even-odd effect. The mesophase temperature range also varies regularly with the polymerstructure. It is shown that the mesophase range has been widened.     

Rapid Determination of HAAs Formation Potential of the Reaction of Humic Acid with Chlorine or Chlorine Dioxide

On the basis of gas chromatography(GC) coupled with a short capillary column and an electron capture detector(ECD), a simple and rapid method for the determination of five haloacetic acids(HAAs) in drinking water was developed by the optimization of derivation conditions and the modification of gas chromatographic program. HAAs formation potential(HAAFP) of the reaction of humic acid with chlorine was determined via this method. The major advantages of the method are the simplicity of chromatographic temperature program and the short run time of GC. Dichloroacetic acid(DCAA) and Trichloroacetic acid(TCAA), which were detected in the determination of HAAFP, were rapidly formed in the first 72 h of the reaction of humic acid with chlorine. HAAFP of the reaction of humic acid with chlorine increased with the increase in the concentrations of humic acid and chlorine. The average HAAFP of the reaction of humic acid with chlorine was 39.9 μg/mg TOC under the experimental conditions. When the concentration of humic acid was 4 mg/L, the concentration of HAAs, which were produced in the reaction of humic acid with chorine, may exceed MCL of 60 μg/L HAAs as the water quality standards for urban water supply of China and the first stage of US EPA disinfection/disinfection by-products(D/DBP) rule; when the concentration of humic acid was 2 mg/L, the concentration of HAAs may exceed MCL of 30 μg/L HAAs for the second stage of US EPA D/DBP rule. When humic acid was reacted with chlorine dioxide, only DCAA was detected with a maximum concentration of 3.3 μg/L at a humic acid content of 6 mg/L. It was demonstrated that the substitution of chlorine dioxide for chorine may entirely or partly control the formation of HAAs and effectively reduce the health risk associated with disinfected drinking water.     

波长对Ag/TiO2催化剂上二氧化碳光催化还原的影响

Photocatalytic reduction of CO2 by water was performed in the presence of a Ag/TiO2 catalyst under illumination by lamps with different wavelengths(254,365,and 400 nm).The yields of the main products(methane and methanol)were higher with the 254 nm lamp than with the 365 lamp while no products were observed with the 400 nm lamp.This was because the electron-hole generation rate increased with increasing energy of irradiation(decreasing wavelength)and there were higher densities of electron states at higher energies in TiO2. The increased efficiency of electron-hole generation with a shorter wavelength irradiation increased the efficiency of the catalyst.The energy of the electrons excited by visible light(400 nm)was too low for CO2 photocatalytic reduction.     

TERNARY COMPLEXES OF Cu(ATP)AND HETEROAROMATIC N BASE-ISOQUINOLINE AND BENZIMIDAZOLE:STABILITY CONSTANT AND STACKING EFFECT

The stability constants of the binary complexes ofCu~(2+) with isoquinoline and benzimidazole as well as the ternarycomplexes of Cu(ATP)with the same ligands have been measuredin aqueous solution spectrophotometrically and a strongstacking interaction between the heteroaromatic ring of theligands and the purine moiety of ATP has been found.The factof this stacking interaction is much stronger than that in thesystems of Cu(ATP)with pyridine and imidazole shows thatthe stacking interaction increases with the size of theheteroaromatic ring of the ligands.     

Investigation on the response factors of concentration detectors within sec process

The response factors of refractive index(RI) and ultraviolet(UV) detectors of size exclusion chromatography (SEC) defined as the ratio of area of output signal to the mass of injected sample are studied and analyzed by using five narrowly distributed polystyrene(PS) standard samples with known molar masses.It is found that the individual response factor for a given sample varies with the concentration of the injected solution within a limited range bounded by an upper and a lower limiting response factor values.This variation reveals the conformational change of the polymer chains with the concentration of the injected solution.The dynamic contact concentrations c_s of the PS samples derived from the response factor data are in good accordance with those reported earlier by other methods.The physical meanings of the signals of the two detectors are further analyzed and theoretically formulated.The solvation of the polymer chain and the conformation changes play an important role in these detecting systems.Both of the solvation number of the structural repeating unit and the extra embedded solvent due to cluster forming in higher concentrations could be deduced from the variation of response factor with the concentration of the injected solution.     

Toughening of ethylene-propylene random copolymer/clay nanocomposites: Comparison of different compatibilizers

Ethylene/propylene-random-copolymer(PPR)/clay nanocomposites were prepared by two-stage melt blending. Four types of compatibilizers,including an ethylene-octene copolymer grafted maleic anhydride(POE-g-MA) and three maleic-anhydride-grafted polypropylenes(PP-g-MA) with different melt flow indexes(MFI),were used to improve the dispersion of organic clay in matrix.On the other hand,the effects of organic montmorillonite(OMMT) content on the nanocomposite structure in terms of clay dispersion in PPR matrix,thermal behavior and tensile properties were also studied. The X-ray diffraction(XRD) and transmission electron microscopy(TEM) results show that the organic clay layers are mainly intercalated and partially exfoliated in the nanocomposites.Moreover,a PP-g-MA compatibilizer(compatibilizer B) having high MFI can greatly increase the interlayer spacing of the clay as compared with other compatibilizers.With the introduction of compatibilizer D(POE-g-MA),most of the clays are dispersed into the POE phase,and the shape of the dispersed OMMT appears elliptic,which differs from the strip of PP-g-MA.Compared with virgin PPR,the Young’s modulus of the nanocomposite evidently increases when a compatibilizer C(PP-g-MA) with medium MFI is used.For the nanocomposites with compatibilizer B and C,their crystallinities(X_c) increase as compared with that of the virgin PPR. Furthermore,the increase of OMMT loadings presents little effect on the melt temperature(T_m) of the PPR/OMMT nanocomposites,and slight effect on their crystallization temperature(T_c).Only compatibilizer B can lead to a marked increases in crystallinity and T_c of the nanocomposite when the OMMT content is 2 wt%.     

Kinetics and Mechanism of Iridium(Ⅲ)-Catalyzed Oxidation of Ethanol Amine by Cerium(Ⅳ) in Sulfuric Acid Media

In this study, the kinetics and mechanism of the iridium(Ⅲ)-catalyzed oxidation of ethanol amine(EAN) by cerium(Ⅳ) in a sulfuric acid medium was investigated using titrimetric technique of redox in a temperature range of 298-313 K. It was found that the reaction is of first order with respect to Ce(Ⅳ) and Ir(Ⅲ), and a positive fractional order with respect to EAN. It was also found that the pseudo-first-order([EAN](》)[Ce(Ⅳ)]) rate constant kobs decreases with the increase of [H ] and [HSO-4]. Under the protection of nitrogen gas, the reaction system can initiate the polymerization of acrylonitrile, indicating the generation of free radicals. On the basis of the experimental results, a suitable mechanism was proposed. From the dependence of kobs on the concentration of hydrogen sulfate, Ce(SO4)2 was found to be the kinetically active species. The rate constants of the rate-determining step together with the activation parameters were evaluated.     

Kinetics and Mechanism of Iridium（Ⅲ）-Catalyzed Oxidation of Ethanol Amine by Cerium（ Ⅳ ） in Sulfuric Acid Media

In this study, the kinetics and mechanism of the iridium(Ⅲ)-catalyzed oxidation of ethanol amine(EAN) by cerium(Ⅳ) in a sulfuric acid medium was investigated using titrimetric technique of redox in a temperature range of 298—313 K. It was found that the reaction is of first order with respect to Ce(Ⅳ) and Ir(Ⅲ), and a positive fractional order with respect to EAN. It was also found that the pseudo-first-order([EAN][Ce(Ⅳ)]) rate constant kobs decreases with the increase of [H ] and [HSO-4]. Under the protection of nitrogen gas, the reaction system can initiate the polymerization of acrylonitrile, indicating the generation of free radicals. On the basis of the experimental results, a suitable mechanism was proposed. From the dependence of kobs on the concentration of hydrogen sulfate, Ce(SO4)2 was found to be the kinetically active species. The rate constants of the rate-determining step together with the activation parameters were evaluated.     

Selective hydrogenation of benzene to cyclohexene over Ce-promoted Ru catalysts

Ru-Ce catalysts were prepared by a co-precipitation method.The effects of Ce precursors with different valences and Ce contents on the catalytic performance of Ru-Ce catalysts were investigated in the presence of ZnSO4.The Ce species in the catalysts prepared with different valences of the Ce precursors all exist as CeO2 on the Ru surface.The promoter CeO2alone could not improve the selectivity to cyclohexene of Ru catalysts.However,almost all the CeO2 in the catalysts could react with the reaction modifier ZnSO4 to form(Zn(OH)2)3(ZnSO4)(H2O)3 salt.The amount of the chemisorbed salt increased with the CeO2 loading,resulting in the decrease of the activity and the increase of the selectivity to cyclohexene of Ru catalyst.The Ru-Ce catalyst with the optimum Ce/Ru molar ratio of 0.19 gave a maximum cyclohexene yield of 57.4%.Moreover,this catalyst had good stability and excellent reusability.     

Binding of nucleosides with the cytotoxic plant alkaloid sanguinarine: Spectroscopic and thermodynamic studies

In spite of a large number of studies of the interaction of the cytotoxic plant alkaloid sanguinarine(SAN) with nucleic acids,the anticancer mechanism of SAN is still not clear.In contrast to the large number of studies of the interaction mechanism of SAN with DNA,there have been relatively few studies of the interaction of SAN with nucleosides.In this work,the interaction of SAN with three nucleosides-thymidine(T),uridine(U),and adenosine(A)-was investigated using a combination of conventional fluorescence and UV-vis spectroscopic techniques;thermodynamic calculations were also carried out at physiological pH 7.2.The binding processes of SAN with the different nucleosides were characterized by hypochromic and bathochromic effects in the absorption spectra of SAN and by the quenching of the fluorescence intensity of SAN.The measurements of fluorescence lifetime,the variations of the absorption spectra of the fluorophore,and the dependence of the quenching on the temperature indicated that the fluorescence quenching is static.The Stern-Volmer plot is nonlinear and approximately quadratic showing that,in this process,one SAN molecule can bind with two nucleoside molecules.These studies,together with our earlier studies of the binding of SAN with cytidine(C) and guanosine(G),showed that the binding constants of SAN with the five nucleosides at T = 308.15,318.15,and 328.15 K decreased in the order C > G > T > U > A and at T = 298.15 K decreased in the order G > C > T > U > A,and that the binding of SAN with the various nucleosides is not only slightly exothermic but also entropy-driven.All these results together with fluorescence quenching experiments advance good evidence concerning the interaction of SAN with various nucleosides.Such studies of the interaction mechanism of alkaloids with DNA may promote the development of new drugs.     

Online Separation and Preconcentration of Gold and Palladium on Amidinothiourea Immobilized Glass Bead for Interference-Free Flame Atom Absorption Spectrometry Determination

Amidinothiourea immobilized glass bead (AGB) was applied as the microcolumn packing for the flow-injection online separation and preconcentration of Au(III) and Pd(II) coupled with FAAS determination. The peak-area absorbance (A) and the peak-height absorbance (H) were all used as the evaluating modes. Au(III) and Pd(II) in 0.50 M HCl solution were absorbed onto AGB completely and then eluted into AAS with thiourea solution. Base metal ions with a concentration of 2.0 mg/mL and anions with a concentration of 20.0 mg/mL caused no interference in the determination of Au(III) and Pd(II). The LODs of Au(III) and Pd(II) for a preconcentration time of 60 s with a sampling flow rate of 5.0 mL/min for 0.20 μg/mL of Au(III) and 0.30 μg/mL of Pd(II) were 2.7 and 6.5 ng/mL with the H mode and 4.6 and 10.2 ng/mL with the A mode, respectively. The RSD of seven replicate determinations of 0.20 μg/mL of Au(III) and 0.30 μg/mL of Pd(II) were 0.018 and 0.024 for the H mode and 0.013 and 0.018 for the A mode, respectively. The method was successfully applied to the determination of Au and Pd in real samples. __________ From Zhurnal Analiticheskoi Khimii, Vol. 60, No. 10, 2005, pp. 1023–1029. Original English Text Copyright ? 2005 by Liu, Pu, Su. The text was submitted by the authors in English.     

Role of the Confined Geometry on the Crystallization of Poly（ethylene terephthlate） Ultrathin Films

The reflection-absorption infrared (RAIR) was employed to study the crystallization kinetic of poly (ethylene terephthalate) (PET) ultrathin films. During isothermal crystallization the thinner PET film shows a slower kinetic compared with the thicker film. Moreover, the final crystallinity of films with various thickness was found decrease with thickness. The result of fitting our data to Avrami equation showed that the Avrami exponents decrease with film thickness.     

Kinetics and Mechanism of the Oxidation of Glycol by Dihydroxyditelluratoargentate(Ⅲ) with Spectrophotometry

The kinetics of the oxidation of glycol by dihydroxyditelluratoargentate (Ⅲ) complex(DDA) was studied in alkaline medium with spectrophotometry(in a temperature range of 16.6-40 ℃).The first-order rates with respect to glycol and Ag(Ⅲ) were all found.The rates increased with the increase in [OH-] and decreased with the increase in [TeO2-4].No effect was found with the addition of KNO3 and no free radical was detected.In view of this,the dihydroxymonotelluratoargentate(Ⅲ) species(DMA) is assumed to be the active species.A plausible mechanism involving a two-electron transfer is proposed,and the rate equation derived from the mechanism can explain all experimental observations.Activation parameters of the rate-determining step and constants are evaluated.     

ESCA STUDIES ON SURFACE COMPOSITION OF SEGMENTED POLYURETHANE

Segmented polyurethanes (SPU) have been used as an important biomedical material, of which the hemocompatibility is determined mainly by the surface properties of the polymer. ESCA has. been used in the present study to characterize the surface composition of SPU samples with different degree of phase segregation. Our experimental results show that (1) the ratio of O/N on polymer-air interface is greater than that in the bulk, i. e., more soft segment is found on the surface than in the bulk average; (2) the soft segment is more abundant on the surface for the sample with better phase segregation; (3) within about 50A thickness of the air facing side the composition variation of the sample with better phase segregation is greater than the sample with poor phase segregation.     

STUDIES ON TiCI4/Mg (OEt)_2/EB SUPPORTED CATALYSTS FOR PROPYLENE POLYMERIZATION

The supported catalysts for propylene polymerization were prepared by milling Mg (OEt)_2 with EB (ethylbenzoate) and treating with TiCl_4 solution. When TiCl_4/(Mg(OEt)_2/EB) (mol.) ratio was increased, decrease in contents of-OEt and Ti of the catalysts was observed, while the content of EB increased. It is proved by analyses of IR, X-ray and XPS that during co-milling Mg(OEt)_2 with EB no reactions have taken place. But after treatment with TiCl_4 solution, Mg(OEt)_2 converts into MgCl_2 and EB coordinates on the resulting MgCl_2 carrier, a surface complex forms.The activity of catalysts,isotacticity and vicosimetric molecular weight of polypropylene increase with the decrease of the content of ethoxyl group. The kinetic curves of propene polymerization obtained with present catalysts system display decay curves. It is found from the triad tacticity calculated from the expanded spectra of methyl carbon region that, ethoxyl group in catalyst has an effect on the configuration of polymer chain.     

SYNTHESIS OF THE 3'-HALF MOLECULE OF YEAST ALANINE tRNA

This paper deals with the synthesis of the 3'-half molecule of yeast alanine transfer RNA (tRNA_y~(Ala)) by ligation with T_4 RNA ligase of three component oligonucleotide fragments corresponding to nucleotides 36-45(Ⅰ), 46-57(Ⅱ) and 58-76(Ⅲ) in succession extending from the 3'-end to the 5'-end. First, in a ratio of acceptor to donor at 1.5 to 1, we adopted a method of three successive reactions, namely, the 5'-phosphorylation of the nonadecamer (Ⅲ), ligation with the dodecamer(Ⅱ) and the 5'-phosphorylation of the ligation product formed; with one isolation step and obtained the 5'-phosphorylated 31mer(46-76) (Ⅳ) in an overall yield of 70%. Then the 31met(Ⅵ) as a donor was ligated with 3 times of decamer(Ⅰ) to form the 41met(36-76) (Ⅴ), the 3'-half molecule of tRNA_y~(Ala)). The yield was 67%. After 5'-phosphorylation, (Ⅴ) was ligated with the natural 5'-half molecule to form the semi-synthetic tRNA_y~(Ala)), which was biologically active, i. e. accepting and transferring (~3H)-alanine into p