乙酰基丙酮络合物催化合成聚乳酸

以钕、钇、锌、铁、钴、镍六种乙酰基丙酮盐Ｍ（ＡｃＡｃ）ｎ成功地催化丙交酯开环聚合成聚乳酸。详细研究了上述乙酰基丙酮盐催化剂品种及其与单体摩尔比［Ｍ（ＡｃＡｃ）ｎ］／［ＬＡ］、温度和时间对聚合反应的影响。结果表明，使用这些催化剂都能得到高于９０％的高聚合转化率；而稀土催化剂在聚合转化率和聚乳酸分子量方面，均显示更好的催化性能；过高的聚合温度和过长的聚合时间会导致聚乳酸的分子量下降。Ｘ－衍射研究表明，以Ｎｄ（ＡｃＡｃ）３催化合成的聚乳酸为非晶聚合物。     

聚乳酸类生物降解性高分子材料研究进展

本文综述了近年来乳酸类合成生物降解材料的合成及应用研究进展。     

乙交酯、L-丙交酯均聚物及其共聚物的制备和性能研究

以辛酸亚锡为催化剂、1,4-丁二醇为引发剂,在高温、高真空条件下本体熔融开环聚合制备了聚乙交酯(PGA)、聚L-丙交酯(PLLA)及其不同比例的共聚物(PLGA).通过红外光谱(IR)、核磁共振(1H-NMR)对聚合物的结构进行了表征,用乌氏黏度计、凝胶渗透色谱仪(GPC)、示差扫描量热仪(DSC)、热重分析仪(TGA)、X射线粉末衍射仪(XRD)、流变仪等对聚合物的特性黏数、分子量与分子量分布、热性能、结晶性、流变性能进行了研究.结果表明PLGA和PLLA具有较高的分子量和窄的分子量分布;PGA、PLLA、PLGA均具有较高的热稳定性,随着PLGA中PGA单元的增加,分解温度逐渐升高.直接熔融合成的PGA在各有机溶剂中溶解性都不理想,用二甲基亚砜(DMSO)重结晶后的PGA在六氟异丙醇(HFIP)中的溶解度增大;PGA、PLLA具有较高的结晶度,而PLGA以非晶态存在,DMSO重结晶后的PGA的结晶度降低.PGA、PLLA、PLGA的熔体均是剪切变稀流体,但PGA、PLLA具有较高的储能模量,PLGA具有较高的损耗模量.相对于PGA和PLLA,无规共聚的PLGA易纯化,并且柔性较好,更易加工,因此PLGA是更适宜的生物可降解材料.     

不同旋光度PLGA的制备及其结晶性能研究

以消旋丙交酯、左旋丙交酯和乙交酯为原料,以辛酸亚锡为引发剂,在高真空条件下本体熔融开环聚合,制得一系列不同旋光度的丙交酯乙交酯共聚物(PLGA),其结构经1H NMR, IR, XRD和DSC表征.并采用DSC研究了PLGA的熔体结晶行为,结果表明其结晶性能随其旋光度的减少而显著降低,甚至不结晶.     

DL—丙交酯与2—氢—2—氧—1,3,2—氧磷杂环己烷的开环共聚合研究

在三异丁基铝催化下ＤＬ－丙交酯与２－氢－２－氧－１，３，２－二氧磷杂环已烷开环共聚，制备了一类新型水溶性共聚物Ｐ（ＬＡ－ｃｏ－ＴＭＰ），用ＨＮＭＲ、ＩＲ谱对其结构进行了表征，并研究了催化剂用量及不同单体配比对总转化率、共聚物组成及特性粘度的影响。     

吡咯茂钐络合物的合成及其催化的丙交酯聚合

本文合成了吡咯修饰的二茂稀土金属有机化合物,并研究了该化合物对丙交酯的聚合,结果显示该化合物可以在很宽的温度范围内实现对丙交酯的高转化率聚合．     

稀土化合物催化内酯开环聚合 Ⅱ．异丙氧基稀土催化D．L－丙交酯开环聚合

 系统地研究了异丙氧基稀土催化Ｄ．Ｌ－两交酯（ＬＡ）开环聚合的规律．实验表明：在甲苯溶剂中，异丙氧基稀土对Ｄ．Ｌ－丙交酯聚合有较高的催化活性，可获得较高的分子量（Ｍη＝４．０×１０^４）不同稀土元素的活性次序如下：Ｌａ＞Ｎｄ＞Ｄｙ＞Ｙ．异丙氧基稀土催化Ｄ·Ｌ－两支酯聚合的合适条件为：［ＬＡ］＝１．９５ｍｏｌ／ｌ，［Ｌｎ（Ｏ－ｉ－Ｐｒ）３］＝６．５×１０^－３ｍｏｌ／ｌ，甲苯，９０℃，聚合反应速度与单体和催化剂浓度均成一级关系，聚合反应表现活化能为着６７．７ｋＪ／ｍｏｌ．     

丙交酯开环聚合反应的新型有机催化剂

作为生物高分子降解材料,聚乳酸具有良好的生物相容性和生物降解性,已经广泛应用于包装材料、农用薄膜等环境领域和药物控制释放体系、医用缝合线、组织工程支架等医学领域。丙交酯开环聚合是制备聚乳酸的理想之选,其催化体系目前以金属催化剂为主,但金属离子在聚合物中的痕量残留和细胞毒性限制了聚乳酸在生物医学及微电子领域的应用,而有机催化剂能够克服这些缺点,是目前聚乳酸合成领域的研究热点。本文从不同的活化机理角度,阐述了近年来有机催化剂在合成聚乳酸中的研究进展,总结了各种催化体系在活性、结构可控性及选择性方面的特点,同时展望有机催化剂在开环聚合反应中所面临的机遇与挑战。     

生物降解材料聚丙交酯的合成及相对分子质量测定——综合性研究型实验设计

介绍一个综合性研究型实验——生物降解材料聚丙交酯的合成及其相对分子质量的测定.整个实验过程不仅包含了有机化学实验的基本操作,而且还涉及当前材料化学领域的研究热点及科研分析方法,是一个涵盖内容丰富,适合高年级应用化学专业学生的综合性实验.     

二(2,6-二叔丁基-4-个甲基苯氧基)钐催化丙交酯开环聚合

聚丙交酯（PLA）可以生物降解，产物无毒，可用于外科手术的缝合线、人造器官以及药物缓释等方面，因此引起了人们的广泛注意．丙交酯的开环聚合是合成聚丙交酯的一种方便方法，所用的催化剂主要是主族及副族金属的配合物，如双金属氧桥配合物［‘j，烷基金属有机化合物［‘j，异丙氧基铝［’‘以及叶琳铝「“等．最近，关于三价烷氧基稀土化合物作为单组份催化剂催化丙交酯开环聚会已有报道［’·’‘．我们发现两价芳氧基稀土化合物（ArO）。Sin（THF）。（ArO一2，已二叔丁基一个甲基苯氧基）也可以有效地催化丙文酯的开环聚合．本…     

(ArO)2Sm(THF)4催化N-苯基马来酰亚胺聚合

发现二价稀土配合物二 ( 2 ,6 二叔丁基 4 甲基苯氧基 )钐 [(ArO) 2 Sm (THF) 4]能较好地引发N 苯基马来酰亚胺 (N PMI)的聚合 ,溶剂对聚合的影响较大 ,在四氢呋喃中聚合转化率最高 ,且聚合转化率随单体浓度的提高而提高 ,而温度对聚合的影响不大。     

Synthesis and Crystal Structure of [（ArO）2Sm（OPPh3）（μ—OH）]2（ArO=2,6—tBu—4—Me—C6H2O）

1 INTRODUCTION In recent years, the syntheses, structures and reactivities of aryloxo lanthanide complexes have attracted a great deal of attention due to their various applications as homogeneous catalysts for organic reactions and precursors for organolan- thanide syntheses[1]. However, the reactivity of divalent lanthanide aryloxides has seldom been studied[2]. We have previously reported that (ArO)2- Sm(THF)4 (ArO = OC6H2-2,6-di-tert-butyl-4-Me) can efficiently initiate the poly…     

二芳氧基稀土氯化物(ArO)2YCl(THF)2·MePh的合成、表征及晶体结构(ArO=2,6-二叔丁基-4-甲基酚基)

无水YCl3 与二倍量的ArONa(ArO =2 ,6 二叔丁基 4 甲基酚基 )在四氢呋喃 (THF)中反应 ,经甲苯溶液重结晶 ,高产率地合成了二芳氧基稀土氯化物 (ArO) 2 YCl(THF) 2 ·MePh。产物经元素分析和核磁共振表征 ,并测定了其晶体结构。配合物属正方晶系 ,I4( 1) /acd空间群 ,晶胞参数为a =1.8913( 1)nm ,b =1.8913( 1)nm ,c =5 .2 2 39( 1)nm ,V =18.6 86 ( 1)nm3 ,Z =16 ,Dc=1.137mg·m- 3 ,μ =1.342mm- 1 (MoKα) ,F( 0 0 0 ) =6 848,R =0 .0 46 9,Rw=0 .112 2。中心金属钇原子与二个芳氧基中的氧原子、一个氯原子和两个THF分子中的氧原子配位 ,形成一个五配位的扭曲的三角双锥几何构型。Y O(Ar)和Y Cl的键长分别为 0 .2 10 1( 3)和 0 .2 5 17( 6 )nm。     

ChemInform Abstract: The Thermodynamic Stability of ArO4

ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.     

配合物(ArO)2Yb(NPh2)2K(THF)4(Ar=C6H2-t-Bu3-2,4,6)的合成、分子结构和催化行为

Reaction of anhydrous YbC13 with 2 equiv, of sodium 2,4,6-tri-tert-butylphenoxide (ArONa, Ar=C6H2-t-Bu3-2,4,6) and 2 equiv, of potassium diphenyl amide in THF afforded the first bis(aryloxo) amido-lanthanide complex of (ArO)2Yb(NPh2)2K(THF)4 (1). In 1, the ytterbium and potassium were bridged via diphenyl amido ligands.The ytterbium metal center was coordinated to two oxygen atoms of aryloxide ligands and two nitrogen atoms of diphenyl amido ligands in a conventional distorted tetrahedral fashion, while the potassium interacted in η^2-fashion with two phenyl rings of the diphenyl amido ligands besides four THF molecules. 1 displayed moderate catalytic activities for the polymerization of methyl methacrylate and acrylonitrile.     

Synthesis and Crystal Structure of [(ArO)_2(THF)Sm(μ-OH)]_2·2THF(Ar=C_6H_(2-)~tBu_3-2,4,6)

1 INTRODUCTION Sm(II) chemistry has been extensively studied due to the strong reduction potential of this 4f6 ion[1]. The transformation of unsaturated substrates by Sm (II) complexes into products with unusual structures is one of the most interesting research areas. For the successful examples reported, Sm(II) starting mate- rials were restricted primarily to cyclopentadienyl complexes[2]. The reactivity of Sm(II) complex with phenolate ligands has seldom been explored. Recen- tl…     

Synthesis and Characterization of Gd2[Pt2(SO4)4(HSO4)2](HSO4)2

Red single crystals of Gd₂[Pt₂(SO₄)₄(HSO₄)₂](HSO₄)₂ (triclinic, , Z = 1, a = 844.02(9), b = 908.50(9), c = 939.49(8) pm, α = 107.73(1)°, β = 112.10(1)°, γ = 103.53(1)°) were obtained by the reaction of [Gd(NO₃)(H₂O)₇][PtCl₆]·4H₂O with sulfuric acid at 320 °C in a sealed glass ampoule. In the crystal structure, Pt₂ dumbbells are coordinated by four chelating sulfate groups and two monodentate hydrogensulfate ions. Two further HSO₄^? ions are not bonded to the Pt₂ dumbbell. The Gd³⁺ ions are eightfold coordinated by oxygen atoms. The IR data of Gd₂[Pt₂(SO₄)₄(HSO₄)₂](HSO₄)₂ are typical for these type of compounds. The thermal decomposition of the compound leads to elemental platinum and Gd₂O₃.     

New layered materials: syntheses, structures, and optical properties of K(2)TiCu(2)S(4), Rb(2)TiCu(2)S(4), Rb(2)TiaAg(2)S(4), Cs(2)TiAg(2)sS(4), and Cs(2)TiCu(2)Se(4)

The new compounds K(2)TiCu(2)S(4), Rb(2)TiCu(2)S(4), Rb(2)TiAg(2)S(4), Cs(2)TiAg(2)S(4), and Cs(2)TiCu(2)Se(4) have been synthesized by the reactions of A(2)Q(3) (A = K, Rb, Cs; Q = S, Se) with Ti, M (M = Cu or Ag), and Q at 823 K. The compounds Rb(2)TiCu(2)S(4), Cs(2)TiAg(2)S(4), and Cs(2)TiCu(2)Se(4) are isostructural. They crystallize with two formula units in space group P4(2)/mcm of the tetragonal system in cells of dimensions a = 5.6046(4) A, c = 13.154(1) A for Rb(2)TiCu(2)S(4), a =6.024(1) A, c = 13.566(4) A for Cs(2)TiAg(2)S(4), and a =5.852(2) A, c =14.234(5) A for Cs(2)TiCu(2)Se(4) at 153 K. Their structure is closely related to that of Cs(2)ZrAg(2)Te(4) and comprises [TiM(2)Q(4)(2)(-)] layers, which are separated by alkali metal atoms. The [TiM(2)Q(4)(2)(-)] layer is anti-fluorite-like with both Ti and M atoms tetrahedrally coordinated to Q atoms. Tetrahedral coordination of Ti(4+) is rare in the solid state. On the basis of unit cell and space group determinations, the compounds K(2)TiCu(2)S(4) and Rb(2)TiAg(2)S(4) are isostructural with the above compounds. The band gaps of K(2)TiCu(2)S(4), Rb(2)TiCu(2)S(4), Rb(2)TiAg(2)S(4), and Cs(2)TiAg(2)S(4) are 2.04, 2.19, 2.33, and 2.44 eV, respectively, as derived from optical measurements. From band-structure calculations, the optical absorption for an A(2)TiM(2)Q(4) compound is assigned to a transition from an M d and Q p valence band (HOMO) to a Ti 3d conduction band.     

SYNTHESES AND CRYSTAL STRUCTURES OF (Et_4N)_2(Fe_2Se_2(SPh)_4) AND (Et_4N)_2(Fe_4Se_4Cl_4)

<正> Since the discovery of iron-sulfur proteins , a number of analogous compounds of the active sites of iron-sulfur proteins has been synthesized and characterized . Due to the similarity between sulfur and selenium, some selenoproteins with similar active site as iron-sulfur proteins were found . We have synthesized a series of iron-selenium compounds in correlative study with the iron-sulfur compounds. In this paper, we will discuss the syntheses and crystal stuctures of the title compounds. The spectroscopic properties of these compounds have been under investigation.