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991.
Changmei Sun Rongjun Qu Qiang Xu Chunnuan Ji Yanzhi Sun 《European Polymer Journal》2007,43(4):1501-1509
Two novel chelating resins were prepared by anchoring ethylenediamine to crosslinked polystyrene via a spacer containing sulfide. Their structures were characterized by Fourier transform-infrared spectra (FTIR) and scanning electron microscopy (SEM). Porous structure parameters of the resins were measured by ASAP 2020 using BET and BJH methods. Their adsorption capacities for several heavy metal ions especially Hg2+ were investigated. The results showed that for the two resins, the more N contents did not mean the better adsorption capacity and the saturated adsorption capacity of poly(2-ethylenediamidomercaptomethylstyrene) (PSM-EDA) for Hg2+ could reach to 3.0 mmol/g at room temperature. Isothermal adsorptions of the resins for Hg2+ could be described by Langmuir formula. The adsorption mechanism of the resins for Hg2+, Cu2+ and Ag+ was confirmed by X-ray photoelectron spectroscopy (XPS) and FTIR. 相似文献
992.
Condensation reaction of 3-(methacryloxypropyl)-trimethoxysilane and diisobutylsilanediol in non-hydrolytic sol-gel process 总被引:1,自引:0,他引:1
Keum-Hee Nam Tae-Ho Lee Byeong-Soo Bae Michael Popall 《Journal of Sol-Gel Science and Technology》2006,39(3):255-260
The condensation reaction of 3-methacryloxypropyl-trimethoxysilane (MPTS) and diisobutylsilanediol (DIBSD) in a non-hydrolytic
sol-gel process was investigated in terms of the reaction time and the catalyst amount for fabrication of inorganic-organic
hybrid materials. The degree of condensation, which was characterized by 29Si NMR, 1H NMR and Abbe refractometry, increases with increased the reaction time and greater catalyst amount. However, a the large
catalyst amount breaks the methacryl group during the condensation reaction. Thus, the reaction time and the catalyst amount
were optimized to synthesize the condensed methacryl oligosiloxanes. 相似文献
993.
Ab initio UMP2 and UQCISD(T) calculations, with 6-311G** basis sets, were performed for the titled reactions. The results show that
the reactions have two product channels: NH2+ HNCO?NH3+NCO (1) and NH2+HNCO?N2H3+CO (2), where reaction (1) is a hydrogen abstraction reaction via an H-bonded complex (HBC), lowering the energy by 32.48
kJ/mol relative to reactants. The calculated QCISD(T)//MP2(full) energy barrier is 29.04 kJ/mol, which is in excellent accordance
with the experimental value of 29.09 kJ/mol. In the range of reaction temperature 2300–2700 K, transition theory rate constant
for reaction (1) is 1.68×1011–3.29×1011 mL·mol-1·s-1, which is close to the experimental one of 5.0×1011mL·mol-1·s-1or less. However, reaction (2) is a stepwise reaction proceeding via two orientation modes,cis andtrans, and the energy barriers for the rate-control step at our best calculations are 92.79 kJ/mol (forcis-mode) and 147.43 kJ/mol (fortrans-mode), respectively, which is much higher than reaction (1). So reaction (1) is the main channel for the titled reaction. 相似文献
994.
A new bismaleimide (BMI) resin was synthesized to formulate epoxy(tetraglycidyl diaminodiphenyl methane; TGDDM) – bismaleimide thermoset blends for composite matrix applications. 4,4′-diaminodiphenyl methane (DDM) was used as an amine curing agent for the TGDDM. A Fourier transform infrared (FTIR) spectroscopy was employed to characterize the new BMI resin. Cure behavior of the epoxy–BMI blends was studied using a differential scanning calorimeter (DSC). DSC thermograms of the thermoset blends indicated two exothermic peaks. The glass transition temperature of the thermoset blends decreased with BMI content. Thermogravimetric analysis (TGA) was carried out to investigate thermal degradation behavior of the cured epoxy–BMI thermoset blends. The new BMI resin reacted partially with the DDM and weak intercrosslinking polymer networks were formed during cure of the thermoset blends. 相似文献
995.
Ederth T Tamada K Claesson PM Valiokas R Colorado R Graupe M Shmakova OE Lee TR 《Journal of colloid and interface science》2001,235(2):391-397
Long-range interactions between self-assembled monolayers (SAMs) of semifluorinated alkanethiols have been studied by direct force measurements in water and aqueous NaCl solutions. SAMs prepared from three different thiols, with identical fluorinated head groups but varying hydrocarbon spacer lengths, were investigated: CF(3)(CF(2))(9)(CH(2))(x)SH, where x=2, 11, or 17. Force measurements show that the interactions in water and electrolyte solutions are composed of both double-layer interactions emerging from what appears to be charges adsorbed onto the surfaces and long-range "hydrophobic" attractions, in excess of the expected van der Waals forces. The three investigated thiols produce similar results in force measurements, though the contact angles with water are slightly different. The "hydrophobic" attraction has the form of step-like attractive discontinuities in the force profiles at separations ranging from 20 to 40 nm, caused by bridging of microscopic bubbles residing at the surfaces. The shape or range of these discontinuities are not significantly affected by replacement of the water with either 1 mM or 1 M NaCl solutions. The origin of the charges causing the electrostatic double-layer interaction is unclear, but some possible causes are discussed. Copyright 2001 Academic Press. 相似文献
996.
Thermal properties of bio flour-filled polypropylene bio-composites with different pozzolan contents
H. -S. Kim S. -W. Choi B. -H. Lee S. Kim H. -J. Kim C. W. Cho D. Cho 《Journal of Thermal Analysis and Calorimetry》2007,89(3):821-827
In this study, the thermal properties of bio-flour-filled, polypropylene (PP) bio-composites with different pozzolan contents
were investigated. With increasing pozzolan content, the thermal stability, 5% mass loss temperature and derivative thermogravimetric
curve (DTGmax) temperatures of the bio-composites slightly increased. The coefficient of thermal expansion (CTE) and thermal expansion
of the bio-composites decreased as the pozzolan content increased. The glass transition temperature (T
g), melting temperature (T
m) and percentage of crystallinity (X
c) of the bio-composites were not significantly changed. The thermal stability, thermal expansion and X
c of the maleic anhydride-grafted PP (MAPP)-treated bio-composites were much higher than those of non-treated bio-composites
at 1% pozzolan content due to enhanced interfacial adhesion. X-ray diffraction (XRD) analysis confirmed the crystallinity
of pozzolan-added bio-composites. From these results, we concluded that the addition of pozzolan in the bio-composites was
an effective method for enhancing the thermal stability and thermal expansion. 相似文献
997.
3d‐Metal mononitrides are studied using the density functional theory method. The lowest spin state for these dimers is obtained using the B3LYP hybrid functional with the 6‐311+G* basis set. The equilibrium geometries, vibrational frequencies, binding energies, Mulliken, and natural orbital population analysis charges, natural orbital electronic configuration, electron affinity, and ionization potential are obtained. Mulliken as well as natural orbital population analysis charges indicate that for all dimers, in cations most of the positive charge localized on the transition metal atom where in anions most of the negative charge localized on nitrogen atom. The binding energies for 3d‐metal mononitrides are higher than those for monocarbides and monoxides. © 2006 Wiley Periodicals, Inc. Int J Quantum Chem, 2007 相似文献
998.
Lee CY Canavan HE Gamble LJ Castner DG 《Langmuir : the ACS journal of surfaces and colloids》2005,21(11):5134-5141
The diversity of techniques used in the synthesis, treatment, and purification of the single-stranded DNA oligomers containing a thiol anchor group (SH-ssDNA) has led to a significant variation in the purity of commercially available SH-ssDNA. In this work, we use X-ray photoelectron spectroscopy (XPS) and time-of-flight secondary ion mass spectrometry (ToF-SIMS) to study how the impurities present in commercially synthesized SH-ssDNA oligomers affected the structure of the resulting DNA films on Au. XPS results indicate that two of the purchased SH-ssDNA oligomers contain excess carbon and sulfur. The molecular fragmentation patterns obtained with ToF-SIMS were used to determine the identity of several contaminants in the DNA films, including poly(dimethylsiloxane) (PDMS), lipid molecules, and sulfur-containing molecules. In particular, the ToF-SIMS results determined that the excess sulfur detected by XPS was due to the presence of dithiothreitol, a reductant often used to cleave disulfide precursors. Furthermore, we found that the SH-ssDNA self-assembly process is affected by the presence of these contaminants. When relatively pure SH-ssDNA is used to prepare the DNA films, the P, N, O, and C atomic percentages were observed by XPS to increase over a 24-h time period. In contrast, surfaces prepared using SH-ssDNA containing higher levels of contaminants did not follow this trend. XPS result indicates that, after the initial SH-ssDNA adsorption, the remaining material incorporated into these films was due to contamination. 相似文献
999.
A sequential injection analysis (SIA) system was developed to monitor the concentration of l-cysteine in biological processes on-line. It is based on the redox reaction of l-cysteine with iron(III) in the presence of 1,10-phenanthroline (phen) and the detection of the red-iron(II)-phen complex with a spectrophotometry. The system was fully automated using software written in the LabVIEW™ development environment. A number of system variables such as the flow rate of the carrier buffer solution, the volume ratio of the sample to the reagents, and the reaction coil length, etc., were evaluated to increase the sensitivity and performance of the SIA system. Under partially optimized operating conditions the performance of the SIA system was linear up to a concentration of l-cysteine of 1 mM (R2 = 0.998) with a detection limit of 0.005 mM and a sample frequency of 15 hr−1. The SIA system was employed to monitor the concentration of l-cysteine on-line in a continuously stirred reactor and a fermentation process of Saccharomyces cerevisiae. The on-line monitored data were in good agreement with the off-line data measured by a HPLC with a fluorescence detector (n = 15, R2 = 09899). 相似文献
1000.