Copolymerization of styrene with butadiene and isoprene using a rare earth catalyst

In the copolymerization of styrene-butadiene and styrene-isoprene, a novel rare earth catalyst system (CF3CO2)(3)Ln/R(3-n)AlH(n)/(CH3)(3)CCH2Br (Ln = Y, La, Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb and Lu; R = Me-, Et-, i-Bu-, and Oct-; n = 0 and 1) has been studied. The 1, 4 unit contents in the copolymers obtained are found to range from 64.4 to 99.6% with St contents of 5.2 to 59.9%, and intrinsic viscosities of 0.1 to 0.5 dl g(-1) measured by i.r., H-1 n.m.r. and C-13 n.m.r. spectra. From the calculated data of linked ratios, a change in the microstructure is induced by the styrene unit, probably adjacent to the butadiene or isoprene unit. An interesting result is that the ratios of styrene unit linked with 1, 2 or 3,4 units in the copolymers are far higher than in copolymers obtained with the nickel catalyst. The experimental results are discussed in terms of rare earth pi-allyl coordination and back-biting mechanism.

二烷基单硫代膦酸萃淋树脂吸附重稀土(Ⅲ)的研究

本文研究了Cyanex302萃淋树脂从硝酸介质中吸附重稀土（Ⅲ），吸附能力为Lu＞Yb＞Tm＞Er＞Ho＞Dy＞Tb＞Gd。考察了平衡水相酸度、稀土浓度、温度等对吸附平衡的影响。计算了重稀土（Ⅲ）间的平均分离系数β~z+1_z＝3．55，表明分离稀土（Ⅲ）的选择性优于HDEHP、HEH／EHP萃淋树脂，有可能用于制备高纯单一重稀土。Cyanex302萃淋树脂饱和吸附稀土（Ⅲ）的红外光谱表明，P＝S键参与了配位。

SrB_6O_(10)中铕和铽的发光

大部分稀土离子都有变价行为,稀土的功能特性与其价态密切相关。铕和铽都有变价行为,Eu~(3+)和Tb~(3+)为电子组态共轭的一对稀土离子,是发光材料的重要激活离子。本文首次在空气中合成了SrB_6O_(10):xEu,yTb荧光粉,研究了它们的光谱特征,发现该体系中Eu~(3+),Tb~(3+)和Eu~(2+)离子共存,并随其掺入Tb~(3+)离子浓度的增加,Eu~(2+)的荧光相对发射强度增强。我们用已提出的关于稀土离子对之间电子组态共轭性与价态变化相关性的结论对此现象进行了解释。这一现象的发现有助于了解固相反应中共轭稀土离子对间的电子转移过程,为新型异常价态稀土化合物的预测与合成,为新材料的设计与制备提供了重要依据。

A new thermoplastic polyimide composite based on 1,4-(3,4-dicarboxyphenoxyl)benzene/4,4'-methylene dianiline

New thermoplastic polyimide (PEI) composites based on 1,4-(3,4-discarboxyphenoxyl)benzene/4,4'- methylene dianiline have been fabricated by the approach of polymerization by the approach of polymerization of monomer reactants (PMR). The chemical and physical behavior of the resin during processing are determined by infrared spectroscopy and rheology. The influence of processing conditions on the composite properties is investigated. The processing, physical and mechanical properties of the composites reinforced with different fibers are presented.

OBSERVATION OF EU2+ AND TB4+ IN SRMG4-EU8+, TB8+

Europium(II) and terbium(LV) drive boon observed in SrMgF4: Eu3+, Tb5+ phosphors which are synthesized in Ar stream. The valence state of europium is influenced by terbium. It is notable that the intensities of electron paramagnetic resonance (EPR) peaks corresponding to Eu2+ are increased when Tb3+ ion is incorporated in SrMgF4:Eu3+ phosphors, while X-ray photoelectron spectra of Tb-8d5/2 in SrMgF4:Eu3+,Tb3+ shows an additional peak at high energy to that of Tb-3d5/2 in SrMgF4: Tb3+, which is due to Tb4+. These phenomena can be explained by an electron transfer mechanism.

ELECTROCHEMICAL-BEHAVIOR OF BIS(2 /17-ARSENOTUNGSTATE) LANTHANATES AND THEIR ELECTROCATALYTIC REDUCTION FOR NITRITE

A series of new catalysts, K-14[Ln(As2W17O61)(2)]. xH(2)O (Ln = La, Pr, Sm, Eu, Gd, Tb, Dy, Tm and Yb) which can electrocatalyze reduction of nitrite are presented and their electrochemical behavior is described in this paper. Bis(2:17-arsenotungstate) lanthanates which are monovacant Dawson derivatives, exhibit two 2-electron and one 1-electron waves, attributed to electron addition and removal from the tungsten-oxide framework that comprises each anion structure. The formal potentials of redox couples are dependent on solution pH. Double-hump principle of formal potentials takes effect with increasing atomic number of lanthanide elements following their special electronic shell structure. The third waves of all the heteropolyanions have good electrocatalytic activities for nitrite reduction at pH 5.0.

ELECTROCATALYTIC OXIDATION OF REDUCED NICOTINAMIDE COENZYMES AT ORGANIC DYE-MODIFIED ELECTRODES

Chemically modified electrodes (CMEs) were prepared by adsorbing different dyes, including methylene blue (MB), toluidine blue (TB) and brilliant cresyl blue (BCB), onto glassy carbon electrodes (GCE) with anodic pretreatment. The electrochemical reactions of adsorbed dyes are fairly reversible at low coverages. The CMEs are more stable in acid solutions than in alkaline ones, which is mainly due to decomposition of the dyes in the latter media. They exhibit an excellent catalytic ability for the oxidation of nicotinamide coenzymes (NADH and NADPH). The formation of a charge transfer complex between the coenzyme and the adsorbed mediator has been demonstrated using a rotating disk electrode. The charge transfer complex decomposition is a slow step in the overall electrode reaction process. Some kinetic parameters are estimated. Dependence of the electrocatalytic activity of the CMEs on the solution pH is discussed.

SOLVENT-EXTRACTION OF TERBIUM(III,IV) PERIODATE COMPLEXES WITH QUATERNARY AMINE

The differences between the solvent extraction of Tb(III) and Tb(IV) periodate complexes with quaternary amine were studied carefully for the first time. The effects of extractant concentration, phase ratio, the pH value of stock solution, salting-out agent, extractant form, diluent, and extraction time were comprehensively investigated. Under optimal conditions the separation factor between Tb(IV) and Tb(III) periodate complexes is over 5.5.

Fluorescence spectroscopy studies on the action of rare earths with bovine serum albumin in multimolecular system

In this paper. the interaction of tripositive terbium ions (Tb3+) with bovine serum albumin (BSA) has been investigated in the presence of some alkaline earth metals and citric acid (Cit) by using fluorescence spectroscopy. The results show that Tb-31. BSA and Cit can form ternary complex BSA . Tb-2. Cit(4) in mu =0.1 mol/l NaCl. pH6.3 hexamethylenetetramine buffer. Other tare earths are able to compete for the same binding site in BSA with Tb3+-. The sequence of con,petition is Eu3+>Pr3+>Yb3+>Gd3+>La3+>Ca2+ and Mg2+ cannot replace Tb bound to BSA.

THE FRACTURE-BEHAVIOR OF PHENOLPHTHALEIN POLYETHER ETHER KETONE AT ELEVATED-TEMPERATURE FOR LONG TERMS

The fracture behavior of phenolphthalein polyether-ether ketone (PEK-C) affected by physical aging at 200 degrees C was studied by tensile experiments, scanning electron microscopy, and differential scanning calorimetry observations. The ductile-brittle fracture transition (DBT) caused by physical aging can be considered as a competition between fracture mechanisms of crazing and shear yielding. The aging time required for the DBT is found to be around 400 h, based on the morphological studies and tensile experiments. The shear yielding component of the mechanical deformation could erase the aging effect, thus a deaging phenomenon occurs. We found that the deaging phenomenon has an intrinsic relationship with the extent of aging in the specimen and as a result of the fracture behavior. (C) 1995 John Wiley and Sons, Inc.

1-羟基蒽醌及其稀土络合物的红外光谱分析

制备了稀土离子Ln_(3+)(Ln=La,Ce,Pr,Nd,Sm,Eu,Gd,Tb,Dy)与1-羟基蒽酿的络合物,测定了它们和氘代1-羟基蒽醌在4000~50cm~(-1)范围内的红外光谱,对观察红外吸收带进行分析和归属.发现了某些对金属离子敏感的谱带,确定了配位键的伸缩振动.

稀土离子与牛血Cu(Zn)-SOD的作用

采用ESR、CD谱和荧光光谱研究了pH=6.3时六次甲基四胺-HCl缓冲溶液中LaCl_3和TbCl_3与Cu(Zn)-SOD的配位作用和结构。Cu(Zn)-SOD可增强Tb~(3+)的荧光发射,Tb~(3+)与Cu(Zn)-SOD有多个配位位置,其中有2个强结合位点,La~(3+)与Tb~(3+)可竞争Cu(Zn)…SOD上相同结合位点,77K下La~(3+)与Tb~(3+)使Cu(Zn)-SOD的Cu~(2+)活性中心的配位环境由菱形对称结构向轴对称结构转变,使Cu(Zn)-SOD的局部结构变松散,但对SOD酶活性基本无影响,表明稀土离子主要与酶蛋白分子中的酸性氨基酸羧基配位,对酶蛋白二级结构仅产生微弱扰动,对活性中心空间结构影响较小,基本不影响Cu(Zn)-SOD酶活性。

MF_2:Eu,Ce(M=Ca,Sr,Ba)中稀土离子的价态变化

我们已经实验证明并报道了Eu-Tb之间、Ce-Yb之间的电荷转移.本文首次实验证实了Ce~(3+)离子和Eu~(3+)离子之间电荷转移现象的存在,进一步阐述了稀土价态与其电子组态共轭特征的相关性.1 实验部分1.1 试剂CaF_2,SrF_2,BaF_2,NH_4HF_2、氢氟酸、盐酸均为分析纯,EuF_3和CeF_3分别由高纯Eu_2O_3(99.95%)及CeO_2(99.99%)自制.1.2 MF_2:Eu,Ce体系的合成按化学计量比(MF_2:X%CeF_2,y%EuF_3;X=1,y=0,0.1,0.3,0.5,1;X=0,0.05,0.1,0.3,0.5,y=1)准确称取原料,放人玛瑙研钵中充分研混后装入刚玉柑涡中,置于管状炉内(用氢气

氟化镁锶中铕和铽的电荷迁移及其平衡解析

在氩气氛中，合成了SrMgF4：xEu，yTb复合组化物磷光体．该体系中Eu3+和Eu2+共存．随共掺入Tb浓度的增加，Eu3+的荧光发射强度降低，Eu2+的发光增强；并且Eu2+的ESR信号增强．认为Eu3+和Tb3+之间存在电荷迁移．即Eu3+＋Tb3+→Eu2+＋Tb4+.通过半定量手段研究了这一电荷迁移反应的平衡常数

稀土离子和肌质网(Ca~(2+)+Mg~(2+))-ATP酶相互作用的研究

研究了稀土离子对肌质网(Ca~(2+)+MG~(2+))-ATP酶活性的影响及其作用机制,结果表明,低浓度Gd~(3+)对肌质网膜上(Ca~(2+)+Mg~(2+)),ATP酶有激活作用,较高浓度Gd~(3+)抑制其活性,Gd~(3+)抑制纯化酶的活性,低浓度Gd~(3+)对磷脂酸(FA)、心磷脂(CL)重组酶有激活作用,而对磷脂酰胆碱(PC)、磷脂酰胆碱(PC)与磷脂酰乙醇胺(Pe)混合物(PC/PE)及磷脂酰丝氨酸(PS)重组酶无激活作用,低浓度Tb~(3+)对肌质网膜与纯化酶上Ca~(2+)结合位点的影响不同。