Poly(2,2-dimethyltrimethylene carbonate)-block-poly(dimethylsiloxane)-block-poly(2,2-dimethyltrimethylene carbonate). Synthesis and thermal properties

Lithium salts of hydroxytelechelic poly(dimethylsiloxane) [poly-(DMS)] were used as initiators for the anionic ring-opening polymerization of 2,2-dimethyltrimethylene carbonate (DTC). Triblock copolymers were obtained in high yields. Complexation of the active site in DTC polymerization by the poly(DMS) chain leads to a decrease in polymerization rate. The thermal properties of the copolymers of different compositions were determined. Catalysed thermal degradation of the block copolymers leads to cyclic oligomers D_n and DTC upon ring-closing depolymerization.     

Random copolymerization of ϵ-caprolactone and trimethylene carbonate with rare earth catalysts

Random copolymerization of trimethylene carbonate (TMC) with ϵ-caprolactone (CL) catalyzed by rare earth chloride-epoxide or rare earth isopropoxide has been investigated for the first time. It was found that in the presence of epoxide, rare earth chlorides have high activities for the copolymerization, giving high-molecular-weight random copolymer P(CL-co-TMC) with a narrow molecular weight distribution. Light rare earth chloride-propylene oxide systems are more effective for the copolymerization than heavy rare earth chloride-propylene oxide systems. For the rare earth chloride-epoxide catalyst system, epoxide is the requisite component, and its amount affects the catalytic activity; while rare earth isopropoxide can catalyze the copolymerization alone. The preparative conditions of the copolymer with NdCl₃-5PO system were studied. The reactivity ratios of CL and TMC copolymerization with NdCl₃-5PO determined by Fineman-Ross method are 1.60 for r_TMC and 0.72 for r_CL, respectively. The copolymers were characterized by ¹H- and ¹³C-NMR, GPC, and DSC. The mechanism study shows that the rare earth alkoxide is the active species that initiates the ring opening copolymerization of CL and TMC with acyl-oxygen bond cleavages of the monomers. © 1997 John Wiley & Sons, Inc. J Appl Polym Sci 64: 2131–2139, 1997     

Isothermal crystallization of random copolymers of ε-caprolactone with 2,2-dimethyltrimethylene carbonate

The isothermal crystallization of three random copolymers of ε-caprolactone with different contents of 2,2-dimethyltrimethylene carbonate (DTC) (DTC: 5, 9 and 18 mol%) and poly(ε-caprolactone) (PCL) was studied using DSC and PLM methods. The isothermal crystallization data were analyzed with the Avrami equation. The exponent n, from 3 of PCL to 2 of P(82%CL-ran-18%DTC), suggests a change of crystal form. The crystallization rate was lowered by the addition of DTC units, which interrupted the perfect crystallization of PCL.     

用新型稀土催化剂催化苯乙烯与异戊二烯共聚合

研究了以亚磷酸二异辛酯为配体的氯化稀土配合物(简称Nd)与三异丁基铝(简称Al)组成的二元稀土催化体系催化苯乙烯与异戊二烯的共聚行为,考察了Al与Nd的摩尔比、聚合温度、单体配比等对共聚行为及共聚物组成和链结构的影响。结果表明,该催化体系能够实现异戊二烯的均聚,但不能催化苯乙烯均聚,而催化二者共聚的活性取决于单体配比且低于异戊二烯的均聚。所得产物为无规共聚物,其中异戊二烯链节以顺式-1,4-结构为主(95%～96%),含少量3,4-结构,几乎不含反式-1,4-结构;共聚物中的结合苯乙烯量随Al与Nd的摩尔比、聚合温度及单体配比中苯乙烯量的增加而增大。苯乙烯以孤立单元形式嵌入在异戊二烯链节之间,因此所得共聚物为"准"无规共聚物;共聚物的重均分子量最高可达19.3×105,分子量分布随着共聚物中结合苯乙烯量的增加而变宽,甚至出现双峰分布。     

Study of NiO cathode modified by rare earth oxide additive for MCFC by electrochemical impedance spectroscopy

The preparation and subsequent oxidation of nickel cathodes modified by impregnation with rare earth oxide were evaluated by surface and bulk analysis. The electrochemical behaviors of rare earth oxide impregnated nickel oxide cathodes were also evaluated in a molten 62 mol% Li₂CO₃+38 mol% K₂CO₃ eutectic at 650 °C by electrochemical impedance spectroscopy (EIS) as a function of rare earth oxide content and immersion time. The rare earth oxide-impregnated nickel cathodes show almost the similar porosity, pore size, and morphology to the reference nickel cathode. The stability tests of rare earth oxide-impregnated nickel oxide cathodes show that the rare earth oxide additive can dramatically reduce the solubility of nickel oxide in a eutectic carbonate mixture under the standard cathode gas condition. The impedance response of all cathode materials at different immersion time is characterized by the presence of depressed semicircles in the high frequency range changing over into the lines with the angles of which observed with the real axis differing 45° or 90° in the low frequency range. The experimental Nyquist plots can be well analyzed theoretically with a modified model based on the well-known Randles–Ershler equivalent circuit model. In the new model, the double layer capacity (C_d) is replaced by the parallel combination of C_d and b/ω; therefore, this circuit is modified to be the parallel combination of (C_d), b/ω, and the charge transfer resistance (R_ct) based on the Randles–Ershler equivalent circuit, to take into consideration both the non-uniformity of electric field at the electrode/electrolyte interface owing to the roughness of electrode surface, and the variety of relaxation times with adsorbed species on the electrode surface. The impedance spectra for all cathode materials show important variations during the 200 h of immersion. The incorporation of lithium in its structure and the low dissolution of nickel oxide and rare earth oxide are responsible for these changes. After that, the structure reaches a stable state. The rare earth oxide-impregnated nickel oxide cathodes show higher catalytic activity for oxygen reduction and lower dissolution of nickel oxide than the pure nickel oxide cathode. The cathode material having 1.0 wt.% of rare earth oxide shows the optimum behavior.     

Direct synthesis of dimethyl carbonate over rare earth oxide supported catalyst

Solid base catalysts for the direct synthesis of dimethyl carbonate (DMC) from carbon dioxide, methanol, and propylene oxide were prepared by loading KCl and K₂CO₃ on the surface of La₂O₃, Y₂O₃, CeO₂ and Nd₂O₃. The catalysts were characterized by thermogravimetric analysis (TGA) and X-ray diffraction (XRD) techniques. The catalytic activities were efficiently influenced by the preparation conditions. The optimal loading amount of K₂CO₃ is 17.6% (mass) for KCl-K₂CO₃/Y₂O₃ and 22.2% for other catalysts. Supports affected the activity of catalyst. KCl-K₂CO₃/Nd₂O₃ exhibited the highest activity. The activity of KCl-K₂CO₃/Y₂O₃ increased with the increase of calcination temperature in the range of 800°C–900°C. The formation of KYO₂, Y₃O₄Cl or YO_X species probably promoted the catalysts. Translated from Natural Gas Chemical Industry, 2006, 31(1): 39–43 [译自: 天然气化工]     

Improving light converting properties with wettability of polyethylene film by rare earth complex Eu(GI)3Phen

ABSTRACT

Modern agriculture needs multifunctional greenhouse films to meet different needs. A novel method for improving light converting properties and wettability of polyethylene film was developed in this paper. Glycerin monostearic acid itaconic acid diester (GI) with a carboxyl group and double band was synthesized. Rare earth complex Eu(GI)₃Phen with Eu³⁺ as central ion has been obtained. Subsequently, a simple strategy of grafting it onto LLDPE backbone was employed to delay the migration of Eu(GI)₃Phen. The fluorescence spectrum indicated that the modified film emitted red light. Meanwhile, the accelerated dripping time of modified film was extended to 12 days.     

含偶氮苯8-羟基喹啉稀土配合物的合成与表征

合成了三种含偶氮苯8-羟基喹啉稀土配合物,通过元素分析、红外、紫外、荧光光谱及热分析,确定了三种配合物的组成为REL3（RE=Sm,Eu,La）,三种配合物在550～650 nm都能产生荧光,峰值（λmax）分别为569,559,552 nm。     

Effect of rare earth additives on properties of silicon nitride ceramics

Abstract

Silicon nitride ceramics with rare earth (Re) compound (5 wt-%) and MgO (3 wt-%) additives were fabricated by spark plasma sintering and following heat treatment. The Re compounds included two groups: ReF₃ ((Re?=?La,Nd,Gd) and Re₂O₃ (Re?=?La,Nd,Gd). Specimens show the same tendency in the sintering shrinkage rate, relative density, grain size and bending strength with the increasing Re cation (Re³⁺) radius both in ReF₃ and Re₂O₃ added samples. However, as to aspect ratios and thermal conductivity, the change rules are completely opposite between the two groups of specimens.     

稀土配合物及其共聚物的合成与性能研究

以丙烯酸(HAA)、甲基丙烯酸(HMA)及1,10-邻菲罗啉(Phen)为配体与氧化铕(Eu2O3)反应得到二元配合物Eu(AA)3、Eu(MA)3和三元配合物Eu(AA)3Phen、Eu(MA)3Phen。将生成的配合物与HMA和甲基丙烯酸甲酯(MMA)共聚,得到一系列三元共聚物。通过元素分析、红外光谱、荧光光谱和热分析对配合物进行了分析与表征,发现配合物具有良好的荧光强度和热稳定性。三元配合物的荧光强度相对于二元配合物有显著提高。共聚物可发射Eu3+的特征荧光,荧光强度随配合物含量的增加而增加,且未发生浓度猝灭现象。三元配合物在反应单体MMA和HMA中的溶解度低于二元配合物,从而使在最大溶解度下二元配合物与反应单体生成共聚物的荧光强度高于相应的三元配合物与反应单体生成的共聚物。     

Copolymerization and polymer blending of trimethylene carbonate and adipic anhydride for tailored drug delivery

The copolymerization in bulk and solution of trimethylene carbonate (TMC) with adipic anhydride (AA) as well as the blending of homopolymers are described. We show experimentally that the components are not copolymerizable but partially miscible, forming a microscopic dispersion without any visible signs of phase separation. Poly(adipic anhydride) (PAA) functions as a plasticizer, permitting an increase in the erosion rate by increasing the porosity and hydration. Drug delivery from the blends was evaluated. A statistical factorial model was designed to explore the influence of three important blend parameters and their interactions, making it possible to predict the erosion and drug‐release behavior of the blend matrices. The PAA:poly(trimethylene carbonate) (PTMC) ratio and molecular weight of the polycarbonate component significantly influence the drug‐release performance, mass loss, and degree of plasticization. The interaction among these factors also influences the blend properties. Plasticization of PTMC enhances the drug release to an extent that is dependent on the amount of PAA used. We demonstrate that blending offers a convenient alternative to copolymerization for the preparation of polymer matrices with predictable drug delivery. © 1999 John Wiley & Sons, Inc. J Appl Polym Sci 72: 227–239, 1999     

稀土钐二元、三元配合物的合成、表征及其生物活性研究

以氯化钐、2-氨基嘧啶和钼酸钠为原料,制备了两种新型稀土钐二元、三元配合物,通过元素分析、紫外光谱、红外光谱等手段对其进行了表征,确定了二元配合物的化学组成为Sm2(AP)(H2O)2Cl3(AP=2-氨基嘧啶),三元配合物的化学组成为:Sm3(AP)(MoO4)2(CH3OH)4Cl5。抗菌结果表明,二元配合物对大肠杆菌和金黄色葡萄球菌的抑菌圈直径分别为13 mm和15 mm,三元配合物分别为13 mm和13 mm,两种配合物对大肠杆菌、金黄色葡萄球菌都有一定的抑制作用。采用MTT法对两种配合物诱导癌细胞凋亡能力做了初步研究,两种配合物的半数抑制浓度IC50在0.001~0.01 mg/mL之间,证明其具有诱导癌细胞凋亡的作用。     

稀土固体超强酸SO2-4/TiO2/La3+合成氯乙酸异丙酯

以稀土固体超强酸SO4^2-／TiO2／La^3 为催化剂,氯乙酸与异丙醇为原料合成氯乙酸异丙酯,系统地研究了投料比、催化剂用量、反应时间诸因素对产品收率的影响。实验结果表明：SO4^2-／TiO2／La^3 是合成氯乙酸异丙酯的良好催化剂,在n(异丙醇)：n(氯乙酸)=3．0,催化剂的用量为氯乙酸质量分数的4．5％,环己烷的用量为反应物总摩尔分数的25％,反应时间4．0h,反应温度90～100℃,氯乙酸异丙酯的收率达到90．7％。     

ICP-MS在稀土元素分析中的应用与作用

稀土元素是指周期表中IIIB族,原子序数21的钪(Sc)、39的钇(Y)和57的镧(La)至71的镥(Lu)共17元素,具有独特的电子构型、特殊的物理、化学性质,使稀土元素在我国工业、国防、医疗、农业等多个不同领域得到广泛应用,稀土元素的分析测试是应用的基础。与其他的分析仪器相比,ICP-MS具有多元素快速分析、精度好、准确度高、低检出限等分析优势,目前,这一技术已在稀土元素分析过程中得到广泛实践应用。     

Implementation of metal-free ring-opening polymerization in the preparation of aliphatic polycarbonate materials

Environmental concerns along with the need to develop aliphatic polycarbonate materials free of any toxic compounds have driven scientists to implement macromolecular engineering processes by replacing potentially toxic and carcinogenic metal-based catalysts traditionally used for the ring-opening polymerization of cyclic carbonates by organic compounds. This issue is of particular importance as aliphatic polycarbonates are gaining increasing credibility for biomedical applications owing to their biocompatibility and bioresorbability. This review provides a complete account of the various metal-free catalysts that has been developed so far as well as comprehensive investigations on the related polymerization mechanisms.     

稀土在高分子材料中的应用

由于稀土元素基本相同的外层电子排布和独特的内层4f电子结构,赋予了稀土元素及其化合物独特的电、光、磁、热等性能,以及界面效应、屏蔽作用和化学活泼性等多种特殊的功能,使其在高分子材料的合成、改性等方面有广泛的应用。作者综述了稀土化合物在高分子催化、聚合物填充、改性等方面的应用。     

Economics of rare earth elements in ceramic capacitors

Ceramic capacitors are an indispensable component in electronic circuits, since they are used in various applications such as timing, filtering, and decoupling. These capacitors are doped with REEs that improve their operating life and electrical properties. In this paper, the economics of rare earth elements (REEs) are reviewed in light of their importance in ceramic capacitors. The developing rare earth element supply and demand crisis that can negatively impact the ceramic capacitor industry and, hence, the global economy, is explained. The cause of this crisis and the response of the world are also discussed.     

Ring-opening polymerization of six-membered cyclic esters catalyzed by tetrahydroborate complexes of rare earth metals

Catalytic behavior of tetrahydroborate complexes of rare earth metals, Ln(BH₄)₃(THF)_x (1: Ln = La, x = 3; 2: Ln = Pr, x = 2; 3: Ln = Nd, x = 3; 4: Ln = Sm, x = 3; 5: Ln = Y, x = 2.5; 6: Ln = Yb, x = 3), for ring-opening polymerization (ROP) of six-membered cyclic esters, δ-valerolactone (VL) and d,l-lactide (d,l-LA), was studied. The controlled polymerization of VL with 1-6 proceeded in THF at 60 °C. The catalytic activities of these complexes for the ROP of VL were observed to be in order of the ionic radii of the metals: 1(La) ≥ 2(Pr) ≥ 3(Nd) > 4(Sm) > 5(Y) > 6(Yb). The obtained polymers were demonstrated to be hydroxy-telechelic by ¹H NMR and MALDI-TOF MS spectroscopy. The controlled ROP of d,l-LA also proceeded by these complexes. The activities of these complexes for the d,l-LA ROP were also in order of the ionic radii of the metals.     

Improvement of corrosion resistance of magnesium metal by rare earth elements

Mg metal containing rare earth metals (REs) can be electrowon directly by molten salt electrolysis. The clarification of the optimum RE content in Mg is necessary to fix the electrolytic conditions in the direct electrowinning of Mg with RE. From this point of view, effect of RE addition in Mg metal on its corrosion property was studied in detail in this study. The specimen was prepared by adding La, Nd, or Ce in melted Mg metal, and its corrosion resistance was examined by an immersion test in 3 mass%-NaCl solution at room temperature. The corrosion resistance of Mg was improved greatly by adding a small amount of RE, whereas the excess addition of RE deteriorated the corrosion resistance. The optimum RE content was about 0.5 mass%. In this study, the corrosion property of Mg with an artificial surface oxide layer was also studied to clarify the effect of surface oxide. The corrosion resistance of Mg was particularly strengthened by conversion coating in a solution including La(NO₃)₃, Nd(NO₃)₃, or Ce(NO₃)₃, with Mg(NO₃)₂. This result suggests that the surface oxide film consisting of both Mg and RE gives ideal corrosion resistance to Mg metal. Mg metal with conversion coating including RE should also be of use as a corrosion-resistant material.     

Preparation and characterization of branched polyesteramide/mix rare earth oxides composites

Branched polyester amide containing various amount of mix rare earth oxides (RE₂O₃) were synthesized by in-situ solution condensation of AB₂ monomer synthesized based on the reaction between maleic anhydride and diethanolamine (DEA). The effect of AB₂ monomer self-polycondensation on the RE₂O₃ surface and the properties of synthesized composites were investigated by using Fourier-transform infrared spectra (FT-IR), ultraviolet–visible absorption spectra (UV–vis), X-ray photoelectron spectroscopy, scanning electron microscopy, thermogravimetric analysis and viscosity determination. AB₂ monomer can envelop RE₂O₃ particles as an organic matrix (HBPEA′) by self-polycondensation under the proposed condition. Ionization of surface of RE₂O₃ aggregates can result in the rare earth ionic (RE³⁺) and the resulting RE³⁺ might coordinate with the organic matrix. Thermal stability of branched polyesteramide can be significantly improved in presence of 5 wt% RE₂O₃, possibly due to the coordination reaction between RE₂O₃ and the active group of the organic matrix.