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981.
Mingli Jiao Kai Yang Wangxi Zhang Wei Pan Ruiwen Zhang Si Xie 《Journal of Macromolecular Science: Physics》2013,52(11):2103-2115
A series of poly(L-lactic acid)/polybutadiene (PLA/PB) biodegradable multiblock elastomers was synthesized and characterized. A two-step process to prepare PLA/PB multiblock elastomers was applied. Melt polymerization was used to prepare poly(L-lactic acid) (PLA) terminated with hydroxyl groups and, at the same time, hydroxyl-terminated polybutadiene (HTPB) and 1,6-hexamethylene diisocyanate (HDI) were employed to synthesize diisocyanate-terminated polybutadiene (ITPB). Then, PLA and ITPB were reacted with different PLA/PB weight ratios. Consequently, a series of PLA/PB biodegradable poly(ester-urethane)s with crosslinked chains was obtained. Swelling characteristics and crosslink density of the crosslinked elastomer were investigated. DMA was applied to characterize its thermal properties. The measurement of mechanical properties showed that a PLA/PB elastomer with adjustable mechanical properties was synthesized. Micromorphology, hydrophobicity, and degradability of the material were also characterized. 相似文献
982.
Kai Xiong Yongping Zhu Lianshi Wang Tongmin Cai Anqiang Zhang Xiangbin Zeng 《Journal of Macromolecular Science: Physics》2013,52(7):1351-1369
Poly(ethene-co-1-butene)-graft-methyl methacrylate-acrylonitrile (PEB-g-MAN) was prepared by suspension grafting copolymerization of methyl methacrylate (MMA) and acrylonitrile(AN) onto PEB. PEB-g-MAN/SAN resin blends (ABMS) were prepared by blending PEB-g-MAN with styrene-acrylonitrile copolymer (SAN resin). The effects of AN/(MMA+AN) feed ratio (fAN), PEB/(PEB+MMA+AN) feed ratio (fPEB) and benzoyl peroxide (BPO) dosage on the monomer conversion ratio (CR), rubber's grafting ratio (GR), grafting efficiency (GE) of the copolymerization and the toughening effect of PEB-g-MAN on the SAN resin were investigated. FTIR quantitative analysis showed that when the weight percent of AN unit in the unextracted product was 21.5 wt% with fAN of 25 wt%, the toughening effect of unextracted PEB-g-MAN on SAN resin was the highest. Gel permeation chromatography (GPC) analysis showed that when fAN was 25 wt%, the grafted copolymer had the lowest molecular weight and ABMS had highest toughness. Transmission electron microscopy (TEM) analysis showed that the highest toughness occurred when the phase structure of ABMS was cocontinuous with fAN of 25 wt%. When fAN was 25 wt% PEB-g-MAN domains have numerous small SAN domains in them, which was occlusion structure. Scanning electron microscopy (SEM) analysis indicated that the ABMS fracture surfaces had plastic flow visible, which looked like a craze fibers morphology, for the sample with highest impact strength (fAN = 25 wt%). Dynamic mechanical thermal analysis (DMA) showed that the miscibility of the PEB phase and SAN phase improved after graft copolymerization of MMA and AN onto PEB. 相似文献
983.
Yanfen Lin Anqiang Zhang Jiannan Sun Lianshi Wang 《Journal of Macromolecular Science: Physics》2013,52(11):1494-1507
Using the characteristics of silica sol dispersing well in water and easy formation of silica gel when the silica sol is heated, by mixing a system of concentrated natural rubber latex and silica sol, the silica sol can in-situ generate SiO2 particles when heated. After coagulation of the mixed system, natural rubber/nanosilica composites C(NR/nSiO2) were obtained. The composites C(NR/nSiO2) and their vulcanizates were studied using a rubber processing analyzer (RPA), dynamic mechanical analysis (DMA), and scanning electron microscopy (SEM). The influence of silica contents on the C(NR/nSiO2) vulcanizates mechanical properties, cross-linking degree, Payne effect, dissipation factor (tanδ), and the particle size and dispersion of SiO2 in NR were investigated. The results obtained were compared with the NR/SiO2 composites based on traditional dry mixing of bale natural rubber and precipitated silica (white carbon black). The results showed that when using a sulfur curing system with a silica coupling agent (Si69) in C(NR/nSiO2), the vulcanizate had better mechanical properties, higher wet resistance, and lower rolling resistance than those without Si69. In the composites C(NR/nSiO2) and their vulcanizates, the SiO2 particles’ average grain diameter was 60 nm, and the good-dispersion of the in-situ generated SiO2 in the rubber matrix were a significant contribution to the satisfactory properties of C(NR/nSiO2) composites and their vulcanizates. 相似文献
984.
The interaction between moxifloxacin (MXFX) and Bovine Hemoglobin (BHb) was investigated at different temperatures by fluorescence spectroscopy. Results showed that the quenching mechanism of MXFX on BHb was a static quenching process with Förester spectroscopy energy transfer. The primary binding for MXFX was located at β-37 Tryptophan residue in hydrophobic cavity of BHb. Besides, weak negative cooperativity was found in drug's binding with BHb. Synchronous spectra revealed that the microenvironment and the conformation of serum albumin were changed during the reaction. Most antibiotics had no effect on the system of BHb-MXFX, except quinolone antibiotics. The system had good stability. 相似文献
985.
ABSTRACT Optimized geometrical structure and harmonic vibration frequencies of prior synthesized (E)-3-phenyl-N-[4-(phenyl-amino) quinazoline-7-yl] acrylamide were computed by ab initio HF and DFT/B3LYP methods using both 6-31G* and 6-311G** basis sets and the Moller–Plesset second-order perturbation (MP2) method merely at the 6-31G* level. The infrared (IR) spectrum of the title compound has been measured in the range of 400–4000 cm?1. Complete vibrational assignments of the IR spectra were proposed. Moreover, the calculated wavenumbers of the title compound were compared with the experimental data. The correlation analyses indicate that good linearity relationships exist between the scaled theoretical vibration frequencies and the experimental values. Additionally, the atoms in molecules (AIM) method was applied to explore the possible intramolecular interactions in the title compound. 相似文献
986.
AbstractPartial least squares model is widely used in estimation of soil physical and chemical parameters such as soil organic matter and moisture content, due to its advantages in dealing with collinearity of variables like hyperspectral reflectance. However, it is hard to determine optimal combination of partial least squares model input for soil organic matter prediction since there are lots of possibilities such as, different mathematical transformation of spectral reflectance, wavelength ranges, and spectral resolution. Laboratory hyperspectral reflectance of soils in Songnen plain were analyzed in this study, and the orthogonal experimental design method for deriving optimal combination of input variables for soil organic matter prediction models was introduced. For intercalating orthogonal experimental design table, five different levels which commonly used by researchers were assigned to factors. Results show that the optimal combination input for single black soil is using the derivative logarithmic reciprocal reflectance in the wavelength range selected by multiple stepwise regression at a spectral resolution of 5?nm (R2=?0.95, RMSE?=?0.21, and RPD?=?4.49), and different soils is using continuum removed in the wavelength range selected by MSR at a spectral resolution of 5?nm (R2?=?0.77, RMSE?=?0.74, and RPD?=?2.08). With optimal combination input, the partial least squares model prediction ability was evaluated as excellent for single black soil, possible for different soils. This study illustrates the orthogonal experimental design method can be an effective way to identify the optimal input variables of a partial least squares model for soil organic matter prediction, and multiple stepwise regression can be a preprocessing step to reduce hyperspectral data redundancy before using partial least squares to predict soil organic matter. Overall, this study provides a new approach for determining optimal input of partial least squares predicting model. 相似文献
987.
AbstractThe interaction of pioglitazone hydrochloride bound to tryptophan residues and tyrosine residues in bovine transferrin was investigated using synchronous fluorescence spectroscopy at various temperatures (298, 310, and 318?K). From binding constants and thermodynamic parameters, it was shown that 1:1 stable compound was formed by the electrostatic force interaction of pioglitazone hydrochloride bound to tryptophan residues and tyrosine residues in bovine transferrin. The extent of binding between pioglitazone hydrochloride and tryptophan residues in bovine transferrin was more than that between pioglitazone hydrochloride and tyrosine residues in bovine transferrin. At 310?K, the fluorescence quenching ratio number of tyrosine residues and tryptophan residues in bovine transferrin were 47.52% and 54.19%, respectively, which indicated that the fluorescence contribution of tryptophan residues was greater. At 310?K, pioglitazone hydrochloride-tyrosine residues(in bovine transferrin) binding rate were 55.60–73.82%, and the combined model was W?=??0.0315R2???0.1520R?+?0.7385. The value of Hill’s coefficients was greater than 1, which suggested that there was a positive cooperativity between pioglitazone hydrochloride and subsequent ligands. The results of molecular docking were consistent with that of experimental calculation. 相似文献
988.
Abstract A new flow‐injection online reduction electrochemical hydride generation system for the determination of Se(IV) and Se(VI) by atomic fluorescence spectrometry (AFS) was developed. In the system, an electromagnetic induction oven was used as heating resource to reduce Se(VI) to Se(IV) and a homemade tubular electrolytic cell as hydride generator. All analytical procedures were automatically controlled by a computer. The conditions of online reduction, including temperature, HCl concentration, and reduction time, have been studied in detail. The detection limits (3σ) of Se(IV) and Se(VI) in aqueous solution were 0.26 µg L?1 and 0.23 µg L?1, respectively. The precision for 11 replicate measurements of 50 µg L?1 Se(IV) and Se(VI) was 2.2% and 2.5%. This proposed method has been applied to the determination of Se(IV) and Se(VI) in springwater samples. 相似文献
989.
ABSTRACT Trace amounts of cerium were analyzed by flow injection kinetic spectrophotometry, based on the decolorization reaction between arsenazo III and Ce(IV) in sulfuric acid medium at room temperature. The absorbance difference (ΔA) of decolorization was linear with the concentration of Ce(IV). The flow injection technique was used to precisely control the timing. Under the optimum conditions, the determination of Ce(IV) in the range 0.0–8.0 µg mL?1 with a correlation coefficient (r) of 0.9982, the regression equation was ΔA = 0.0014 + 0.0406c (µg mL?1). The detection limit (3σ) of 0.2 µg mL?1 was achieved at a sampling frequency of 60 h?1. The proposed method was applied to the analyses of Ce in soil successfully. 相似文献
990.
ABSTRACT A new catalytic kinetic fluorescent quenching method for the determination of trace gold(III) was investigated. The method was based on the catalytic effect of gold on oxidation of 3-(3′-methylphenyl)-5- (2′-arsenoxylphenylazo) rhodanine by hydrogen peroxide in potassium hydrogen phthalate–hydrochloric acid (pH = 3.4). Under the optimum conditions, the great decrease of fluorescence intensity has a linear relationship against the concentration of gold in the range of 0 to 12.0 µg·L?1 with a detection limit of 6.0 × 10?10g·L?1. The coexistent metal ions can be separated, and gold can be enriched by TBP resin of solid-phase extraction, which greatly improves the selectivity and sensitivity of the system. The method can be used to determine trace amounts of gold in ore samples successfully with satisfactory results. 相似文献