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The organic salts as initiators [A~+B~-:Ph_3C~+ClO_4~-, Ph_3C~+SbCl_6~-, (-)Sp~+ClO_4~- and(-)(Sp)_2~(+3)(ClO_4)_3] and catalysts [A~+B~-:(+)CSA, A~+B~-:Ph_3C~+(+)CSA~- and(-)Sp~+(+)CSA] are prepared and characterized by specific rotation. The asymme-trically stereoselective induction of the initiators and catalysts in the polymerization ofN-vinylcarbazole is in an order of A~+B~->A~+B~->A~+B~-. The specific rotations ofobtained poly (N-vinylcarbazole ) (PVCZ) generally are in accordance with mentioned order. 相似文献
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The structure and properties of poly(N-vinylcarbazole) (PVCZ) obtainedvia asymmetrically stereoselective polymerization have been studied by using ~1HNMRspectra, UV spectra, DSC analysis and GPC. The steric microstructure i.e. the contentof isotactic sequences was found to be increased by using AIBN to (-)Sp~+(+)CSA~- asthe initiators or catalysts and the mole extinction coefficient to be decreased. Bimodalmolecular weight distribution (MWD)s of the obtained PVCZs were caused by two propa-gating species of the free ions and the ion-pairs associated with the organic salts duringpolymerization. 相似文献
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IntroductionElieletal.1,2 haveeverreportedthatsolventtypeandconcentrationwouldaffecttheequilibriumofcis 3 hydrox ythiane S oxideconformationwhichwascausedbyintermolec ularandintramolecularhydrogenbondformedwiththeinter actionbetweenthesolute solventandthesolute soluteinthesolutionandhaveimportantinfluenceonitsspecificrotation .Uptonowitisnotveryclear,however,whetherhydrogenbondingaffectsspecificrotation (inmagnitudeandoccasion allyinsign)directlyorwhetheritdoessoindirectly (byaf fectingconform… 相似文献
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The copolymerization process of triphenylmethyl methacrylate (TrMA) and methylmethacrylate (MMA) using chiral anionic complex initiator (-) SP-FlLi (Scheme 1) has beenstudied in toluene and THF, respectively. The copolymer obtained in toluene possessed muchhigher specific rotation than that in THF. These copolymers have shown a tendency to a random and a like alternating structure, respectively. 相似文献
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INTRODUCTIONAnionic polymerization of MMA could be carried out with alkyllithium or Grignard reagent etc. in a non-polarsolvent. However, this polymerization system often involves multiple active species and side reactions dependingon initiator, countercation, solvent and polymerization temperature etc. Therefore, the molecular weightdistribution and stereomicrostructure of PMMA obtained would be very different[1-4]. These differences wouldbe mainly caused by the nucleophilic attack of… 相似文献
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在前文研究聚乙烯醇(PVA)对丙烯酰胺聚合反应效应的基础上,本文进一步研究了PVA对N-取代丙烯酰胺衍生物聚合反应的影响。发现PVA对N-甲基丙烯酰胺的聚合反应亦有减速作用,且减速程度与添加的PVA量间有一定量关系。而PVA对N,N-二甲基丙烯酰胺的聚合反应就无此效应。为考察PVA同丙烯酰胺AM类单体间的相互作用,进行了粘度测定,并采用(化学电离)质谱的方法证实了AM及N-甲基丙烯酰胺同1,3-丙二醇间所存在的分子缔合作用。对缔合物的形或模式进行了探讨。 相似文献
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The changes of the specific rotation and sign of optically active BINOL have been studied in polar/non-polar solvents and at the different pH values of solvent.It is considered that these changes are determined by the equilibriurn studies between cisoid and transoid conformations of BINOL with the same configuration(R or S) which related to the change of the dihedral angle between two naphthalene ring planes of BINOL. 相似文献
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A new kind of dendronized poly(methylsiloxane) (3a and 3b) with appendent Fre-chet-type poly(aryl ether) dendrons has been synthesized and characterized by GPC, DSC, TGA, fluorescence and UV-Vis spectra. 相似文献