Syntheses and properties of novel polyimides derived from 2-(4-aminophenyl)-5-aminopyrimidine

2-(4-Aminophenyl)-5-aminopyrimidine (4) is synthesized via a condensation reaction of vinamidium salts and amidine chloride salts, followed by hydrazine palladium catalyzed reduction. A series of novel homo- and copolyimides containing pyrimidine unit are prepared from the diamine and 1,4-phenylenediamine (PDA) with pyromellitic dianhydride (PMDA) or 3,3',4,4'-biphenyl tertracarboxylic dianhydride (BPDA) via a conventional two-step thermal imidization method. The poly(amic acid) precursors had inherent viscosities of 0.97-4.38 dL/g (c = 0.5 g/dL, in DMAc, 30 degrees C) and all of them could be cast and thermally converted into flexible and tough polyimide films. All of the polyimides showed excellent thermal stability and mechanical properties. The glass transition temperatures of the resulting polyimides are in the range of 307-434 degrees C and the 10% weight loss temperature is in the range of 556-609 degrees C under air. The polyimide films possess strength at break in the range of 185-271 MPa, elongations at break in the range of 6.8-51%, and tensile modulus in the range of 3.5-6.46 GPa. The polymer films are insoluble in common organic solvents, exhibiting high chemical resistance.

Preparation, patterning and luminescent properties of oxyapatite La-9.33(SiO6)(4)O-2 : A (A = Eu3+, Tb3+, Ce3+) phosphor films by sol-gel soft lithography

Silicate oxyapatite La-9.33 (SiO6)(4)O-2:A (A = Eu3+, Tb3+ and/or Ce3+) phosphor films and their patterning were fabricated by a sol-gel process combined with soft lithography. X-ray diffraction (XRD), Fourier transform infrared spectroscopy, atomic force microscopy, optical microscopy and photoluminescence spectra, as well as lifetimes, were used to characterize the resulting films. The results of XRD indicated that the films began to crystallize at 800degreesC and the crystallinity increased with the increase in annealing temperatures. Transparent nonpatterned phosphor films were uniform and crack-free, which mainly consisted of rodlike grains with a size between 150 and 210 nm. Patterned thin films with different bandwidths (20, 50 mum) were obtained by the micromoulding in capillaries technique. The doped rare earth ions (Eu3+, Tb3+ and Ce3+) showed their characteristic emission in crystalline La-9.33(SiO6)(4)O-2 phosphor films, i.e. Eu3+ D-5(0)-F-7(J) (J = 0, 1, 2, 3, 4), Tb3+ D-5(3,4)-F-7(J) (J = 3, 4, 5, 6) and Ce3+ 5d (D-2)-4f (F-2(2/5), F-2(2/7)) emissions, respectively. Both the lifetimes and PL intensity of the Eu3+, Tb3+ ions increased with increasing annealing temperature from 800 to 1100 degreesC, and the optimum concentrations for Eu3+, Tb3+ were determined to be 9 and 7 mol% of La3+ in La-9.33(SiO6)(4)O-2 films, respectively. An energy transfer from Ce3+ to Tb3+ was observed in the La-9.33(SiO6)(4)O-2:Ce, Tb phosphor films, and the energy transfer efficiency was estimated as a function of Tb3+ concentration.

Geometries and electronic properties of AunPdm (n=1-4, m =-1, 0, 1) clusters

Possible conformers for AunPdm (n = 1-4, m = -1, 0, 1) clusters have been presented and studied by use of density functional theory. The results indicate that for n = 2, linear conformer with C-infinityv symmetry is the most stable for anion species, while for cation and neutral species, conformer with C-2v symmetry is the most stable. For n = 3, 4, conformers with C-2v symmetry (kite-shape) are energetically favored. The calculated electron affinities (EAs) and vertical detachment energies (VDEs) are in good agreement with experiments for n = 1-4. It is also interesting to note that for even n (n = 2, 4), the most stable conformers do not give the best agreement between calculated and experimental EA and VDE values, while for odd n (n = 3), the lowest energy conformer also gives the best agreement. The ionization potentials (IPs) of AunPd clusters are calculated as well.

一种新的橙红色长余辉荧光材料Y_2O_2S∶Sm~(3+)

铜激活的硫化锌 (Zn S∶ Cu)和铕激活的硫化钙 (Ca S∶ Eu)是最早获得应用的蓝色和红色长余辉材料 .随后 ,相继发现了铝酸盐体系和硅酸盐体系两大类长余辉荧光材料 [1～ 3 ] .这两类长余辉荧光材料在发光亮度、余辉时间、稳定性方面都较前述硫化物系列长余辉荧光材料有很大提高 ,从而具有非常广阔的应用前景和应用范围 [4～ 6] .但这两类长余辉荧光材料的发光颜色一般为蓝紫、蓝或黄绿 ,没有红色发光现象 .随着研究的深入 ,人们发现了稀土元素激活的碱土钛酸盐红色长余辉荧光材料 ,这种荧光材料在发光亮度及余辉上都有明显的提高 [7,8] ,而且解决了硫化物不稳定的缺点 .近年来才发展起来的以碱土金属氧化物为发光基质 ,以 Eu3 + 为激活剂的红色长余辉荧光材料进一步提高了余辉亮度及时间 [9] .传统碱土硫化物类磷光体有较宽的激发谱带 ,可在不同的光源下激发 .但它的稳定性较差 ,必须进行工艺后处理才能得到应用 .其它几类磷光体的激发光源谱带较窄 ,仅限于紫外光源 ,因此使其应用范围受到限制 .目前已报道的各种长余辉红色荧光材料在余辉时间方面有较大的差异 ,从十几分钟到几百分钟不等 ,各类红色磷光...

La_(4-x)(P_2O_5)_3:Eu_x的合成及光谱性质

磷酸盐是一类十分稳定的晶体化合物 ,易形成 P— O键的多酸根聚合体[1 ] ,以直键或环状排列 ,它们能与稀土离子形成稳定的化合物。作为稀土发光材料的基质 ,具有吸收能力强、转换效率高、物理化学性质稳定、能承受大功率的电子束和高能射线等优点 ,在光致发光 [2 ] 、电致发光[3] 、阴极射线发光 [4 ] 和X射线发光 [5] 等方面获得了广泛的应用。近年来 ,关于稀土焦磷酸盐的合成已有不少的报道。常用的方法是高温固相法 [6 ] ,用此方法合成的样品虽然亮度高 ,但纯度较低 ,粒度不均匀 ,所以探索合成稀土焦磷酸盐的新方法十分有必要。本文采用液相法合成稀土焦磷酸盐 ,通过对产物的 X射线衍射图的分析来探索合成稀土焦磷酸盐的最佳酸度和最佳锻烧温度 ,并对产物的激发光谱和发射光谱作了分析 ,此方法具有纯度高、粒度小和工艺简单等特点。La4 - x(P2 O5) 3:Eux 的合成 :准确称取 1 0 .0 0 0 0 g La2 O3(99.99% )和 2 .0 0 0 0 g Eu2 O3(99.99% ) ,分别用浓 HNO3(优级纯 )溶解完全 ,加蒸馏水配制成 0 .1 mol/ L 的 La(N...

Y_2O_3∶Eu~(3+)发光薄膜的溶胶凝胶法制备、表征及图案化

采用Pechini溶胶 凝胶法制备了纳米级Y2O3∶Eu3+发光薄膜,同时,通过软石印技术得到了条纹宽度为5～60μm的Y2O3∶Eu3+图案化发光薄膜。通过X射线衍射(XRD)、付里叶变换 红外光谱(FT IR)、原子力显微镜(AFM),光致发光(PL)光谱及寿命等方法对得到的发光薄膜进行了表征。XRD结果表明500℃时薄膜开始结晶,900℃已结晶完全,得到了立方相的产物。图案化的条纹在烧结的过程中发生了明显的收缩(50%)。Y2O3基质向掺杂的稀土离子Eu3+发生了有效的能量传递,使得Eu3+显示出5D0 7FJ(J=0,1,2,3,4)特征发射。寿命和光致发光光谱的研究表明,发光强度随着温度的升高而增强。

Formation of a self-assembled monolayer of 2-mercapto-3-n-octylthiophene on gold

Monolayer assembly of 2-mercapto-3-n-octylthiophene (MOT) having a relatively large headgroup onto gold surface from its dilute ethanolic solutions has been investigated by electrochemistry. An electrochemical capacitance measurement on the permeability of the monolayer to aqueous ions, as compared with its alkanethiol counterpart [CH3(CH2)(9)SH (DT)] with a similar molecular length, shows that the self-assembled monolayers (SAMs) of MOT can be penetrated by aqueous ions to some extent. Furthermore, organic molecular probes, such as dopamine, can sufficiently diffuse into the monolayer because a diffusion-limited current peak is observed when the dopamine oxidation reaction takes place, showing that the monolayer is loosely packed or dominated by defects. But the results of electron transfer to aqueous redox probes (including voltammetry in Fe(CN)(6)(3-/4-) solutions and electrochemical ac impedance spectrum) confirm that the monolayer can passivate the gold electrode surface effectively for its very low ratio of pinhole defects. Moreover, a heterogeneous patching process involving addition of the surfactants into the SAMs provides a mixed or hybrid membrane that has superior passivating properties. These studies show that the MOT monolayer on the electrode can provide an excellent barrier for hydrated ionic probe penetration but cannot resist the organic species penetration effectively. The unusual properties of the SAMs are attributed to the entity of the relatively large thiophene moiety between the carbon chain and the thiol group.

杂多酸K7Fe^3＋P2W17O62H2对硫醇—磷脂杂化双层膜通透性的影响

利用涂抹冷冻法制备了硫醇－磷脂杂化双层膜，采用循环伏安和交流阻抗方法，研究了硫醇－磷脂杂化双层膜与杂多酸K7Fe^3+P2W17O62H2作用前后通透性的变化。发现该种杂多酸能够诱导硫醇－磷脂杂化双层膜产生一些孔洞，降低了膜电阻，增加了膜电容，也增加了探针Fe(CN)6^3-/4-与电极的电子传递。同时对产生该现象的机理进行了初步的探讨。

Synthesis and properties of aromatic polyimides derived from 2,2,' 3,3 '-biphenyltetracarboxylic dianhydride

2,2,'3,3' -Biphenyltetracarboxylic dianhydride (2,2,'3,3'-BPDA) was prepared by a coupling reaction of dimethyl 3-iodophthalate. The X-ray single-crystal structure determination showed that this dianhydride had a bent and noncopolanar structure, presenting a striking contrast to its isomer, 3,3,'4,4'-BPDA. This dianhydride was reacted with aromatic diamines in a polar aprotic solvent such as N,N-dimethylacetamide (DMAc) to form polyamic acid intermediates, which imidized chemically to polyimides with inherent viscosities of 0.34-0.55 dL/g, depending on the diamine used. The polyimides from 2,2,'3,3'-BPDA exhibited a good solubility and were dissolved in polar aprotic solvents and polychlorocarbons. These polyimides have high glass transition temperatures above 283 degrees C. Thermogravimetric analyses indicated that these polyimides were fairly stable up to 500 degrees C, and the 5% weight loss temperatures were recorded in the range of 534-583 degrees C in nitrogen atmosphere and 537-561 degrees C in air atmosphere. All polyimides were amorphous according to X-ray determination. (C) 1999 John Wiley & Sons, Inc.

Mossbauer spectra of Fe-57 in a thick film of YBa2(Cu0.97Fe0.03)(3)O7-x irradiated by a large dose of gamma-rays

Mossbauer spectra of Fe-57 in a thick film YBa2(Cu0.97Fe0.03)(3)O7-x irradiated by a large dose of gamma-rays from Co-60 have been measured. The variation of the relative intensities of some subspectra of Fe-57 in the. Mossbauer spectra of the thick film YBa2(Cu0.97Fe0.03)(3)O7-x after irradiation can be observed. This variation indicates that the change of the coordination environment around some Fe atoms in the lattice occurs due to irradiation. The relative intensity of subspectrum D1(Fe) at the Cu(1) site decreases and that of subspectrum D4(Fe) at the Cu(1) site increases. This may be because of the possible oxygen atom hopping between the coordination environments of D1(Fe) and D4(Fe) in the lattice caused by irradiation. The effect of irradiation on the coordination environment around the Fe atom at the Cu(2) site is not appreciable. (C) 1997 Elsevier Science B.V.

α-羰基烯酮环二硫代缩醛化学(XXXVI)──β,β-1,3-亚丙二流基-α,β-不饱和芳酮与Grignard试剂加成物的硅胶催化分解反应

以β，β-1，3-亚丙二硫基-α，β-不饱和芳酮2与烯丙基或等基Grfenard试剂可选择性地进行1，2-加成得醇3、4，在硅胶G的催化下，醇3、4可分解生成β，γ-不饱和芳酮5、6．并对该分解反应的机制进行了初步探讨.

Eu~(3+)在YAG中的发光性能及Eu~(3+)、Bi~(3+)间的能量传递

ＹＡＧ作为一种新型的功能材料已引起了人们极大的兴趣，我们采用溶胶、凝胶法合成了ＹＡＧ：Ｅｕ和ＹＡＧ：Ｅｕ，Ｂｉ，研究了Ｅｕ３＋在ＹＡＧ中的发光及Ｅｕ３＋，Ｂｉ３＋间的能量传递。１实验部分将纯度９９．９９％Ｙ２Ｏ３，Ｅｕ２Ｏ３和Ｂｉ２Ｏ３分别溶于ＧＲ级ＨＮＯ３中，配制成一定浓度的溶液，然后以Ｙ（ＮＯ３）３，Ｅｕ（ＮＯ３），Ｂｉ（ＮＯ３）３和Ａｌ（ＮＯ３）３为初始原料，按（Ｙ１－ｘＥｕｘ）３ＡＬ５Ｏ１２和（Ｙ１－ｘ－ｙＥｕｘＢｉｙ）３Ａｌ５Ｏ１２化学式量配比，充分混匀后加入柠檬酸，缓慢蒸干，在４００℃灼烧２ｈ

Gas permeability in polyimides from oxydianiline and isomeric thiaphthalic dianhydride or 1,4-bis(dicarboxyphenoxy) benzene dianhydride

The gas permeability and permselectivity properties were investigated of polyimides, prepared from 3,3',4,4'- and 2,2',3,3'-thiaphthalic dianhydride (p-TDPA and m-TDPA, respectively), or 1,4-bis(3,4-dicarboxyphenoxy)- and 1,4-bis(2,3-dicarboxyphenoxy) benzene dianhydride (p-HQDPA and m-HQDPA, respectively), and 4,4-oxydianiline. The polyimides prepared from meta-dianhydrides, which have lower chain-segment packing density, possess higher permeability and lower permselectivity than those prepared from para-dianhydrides. Copyright (C) 1996 Elsevier Science Ltd.

STATISTICAL THERMODYNAMICS IN THE FRAMEWORK OF THE LATTICE FLUID MODEL .3. BINARY MIXTURE OF POLYDISPERSE POLYMERS OF SPECIAL DISTRIBUTION WITH STRONG-INTERACTIONS

For a binary mixture of polydisperse polymers with strong interactions, the free energy, the equation of state, the chemical potentials and the spinodal are formulated on the basis of the lattice fluid model. Further, the spinodal curves for the system wi