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121.
SYNTHESIS OF TRIBLOCK COPOLYMERS OF STYRENE AND ISOPRENE BY A NITROXIDE-MEDIATED LIVING FREE RADICAL POLYMERIZATION 总被引:1,自引:0,他引:1
The controlled free radical polymerization of styrene and isoprene initiated with benzoyl peroxide (BPO) in the presence of 2,2,6,6-tetramethyl piperidine-N-oxyl (TEMPO) at 125 ℃ were performed. The obtained polyisoprene and polystyrene homopolymers served as macroinitiators for block copolymerization of isoprene and styrene to synthesize poly(styrene-b-isoprene) and poly(isoprene-b-styrene) diblock copolymers. Diblock copolymers with well-defined structures as well as controlled and narrow molecular weight distribution wereobtained from the lower-mass polystyrene and polyisoprene homopolymers. These copolymers were found to be active as macroinitiators in the synthesis of the poly(styrene-b-isoprene-b-styrene) and poly(isoprene-b-styrene-b-isoprene) triblock copolymers. 1H-NMR spectroscopy and gel permeation chromatography (GPC) were used for the investigation of polymer strucmre, molecular weight and polydispersity (PD). 相似文献
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Simultaneous determination of phenol and mononitrophenol isomers using PLS regression and conventional and derivative spectrophotometry 总被引:1,自引:0,他引:1
The partial least squares regression method (PLS) was tested as a calibration procedure for the simultaneous determination of phenol, o-nitrophenol, m-nitrophenol and p-nitrophenol by both conventional and first derivative UV/Vis spectrophotometry. The experiments were conducted in the acidic, neutral and basic media. The results obtained by the application of the PLS procedure on the conventional and first derivative spectra in two solvent media were compared. It was found that the results obtained in the basic medium have better performance characteristics than those obtained in the acidic or neutral media. Comparable results were obtained in the case of both conventional and first derivative absorbance data. The proposed method was applied to the determination of the four phenol derivatives in natural spiked water samples at concentration levels between 1.0 and 10.0 microg ml(-1) with average recoveries in the range 96% - 99%. 相似文献
124.
Morteza Akhond Mohammad Bagher Najafi Javad Tashkhourian 《Analytica chimica acta》2005,531(2):179-184
In this study, a new poly(vinyl chloride) (PVC) membrane sensor for La3+ ion based on 2,2′-dithiodipyridine as an ion carrier was prepared. This electrode revealed good selectivity for La3+ over a wide variety of other metal ions. Effects of experimental parameters such as membrane composition, nature and amount of plasticizer, the amount of additive and concentration of internal solution on the potential response of La3+ sensor were investigated. The electrode exhibited a Nernstian slope of 20.0 ± 1.0 mV per decade of La3+ over a concentration range of 7.1 × 10−6 to 2.2 × 10−2 M of La3+ in the pH range 3.3-8.0. The response time was about 7 s and the detection limit was 3.1 × 10−6 M. The electrode can be used for at least 2 months without a considerable divergence in potential. The proposed electrode was used as an indicator electrode in potentiometric titration of oxalate and fluoride ions and was applied for determination of F− ion in mouthwash solution. 相似文献
125.
Ahmad O. Baghlaf Khalid Banaser Hussain Y. Hashem Ahmed Albishry Muhammad Ishaq 《Transition Metal Chemistry》1996,21(1):16-18
Summary [RuCl2(CO)2]
n
reacts with the Schiff base 1-acetylferrocenethiosemicarbazone, [Fe(-Cp)(-C5H4MeC=NN-HCSNH2)] to give [Fe(-Cp)(-C5H4MeC=NN-HCSNH2)RuCl2(CO)2] and with 1-acetylferrocenesemicarbazone [Fe(-Cp)(-C5H4MeC=NN-HCSNH2)] to give [Fe(-Cp)(-C5H4MeC=NN-HCSNH2)RuCl2-(CO) 2]. Spectroscopic data indicate that the Schiff bases act as bidentate ligands and coordinate to ruthenium via the hydrazinic N and either the S or O atoms, respectively, giving stable heterobimetallic complexes, which have been characterized by i.r. and 1H-n.m.r. spectroscopies, and elemental analyses.Part of this work was presented at the First International Conference in Chemistry and its applications in Doha, Qatar, 1993. 相似文献
126.
meso-Tetraarylporphyrins are synthesized from pyrrole and aryl aldehydes cleanly and efficiently in one pot at room temperature using equimolar amount of CF3SO2Cl in the presence of air as oxidant. By this novel method 5,10,15,20-tetraarylporphyrins can be prepared in excellent yields. 相似文献
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We are concerning here with the existence of at least one positive continuous solution of coupled systems of quadratic integral equations of fractional orders. Then an existence theorem for a coupled system of Cauchy problems will be proved. 相似文献