尼龙1216晶型转变的红外光谱研究

采用变温红外光谱研究了尼龙1216的Brill转变并测得Brill温度约为150℃。一些α谱带在转变过程中消失，氢键强度也急剧减弱。这些现象证明了Brill转变的“局部熔融”机理。     

AB2星型杂臂共聚物的合成及其结晶行为

通过分子设计, 用过量丁二酸酐将单硬酯酸甘油酯的两个羟基转变为羧基, 再以辛酸亚锡为催化剂, 二苯醚为共沸脱水剂, 使其进一步与不同分子量的端羟基聚乙二醇在负压下共沸脱水偶联, 成功地制备了一系列AB2星型杂臂共聚物, 并采用1H NMR、XRD、DSC、FTIR和偏光显微镜等手段对产物及其结晶行为进行了研究. 1H NMR测试结果表明, 所得聚合物是以二丁二酸甘油酯为核, 一条硬酯酸烷基(GMS)臂和两条聚乙二醇(PEG)臂构成的AB2星型杂臂共聚物[GMS-(SA-PEG)2]. DSC和XRD测试结果表明, 在GMS-(SA-PEG)2中, GMS臂和PEG臂都能结晶; GMS臂的存在不仅影响PEG臂的结晶速度, 同时也影响其结晶的完善程度, 导致结晶温度和结晶熔融温度发生变化; GMS臂相对含量越大, 对PEG结晶行为的影响也越大. 利用偏光显微镜对结晶过程的在线观察结果表明, GMS-(SA-PEG)2的结晶形貌不同于线型聚乙二醇的大球晶, 其先形成细碎的束状晶核, 然后逐步出现生长中的球晶结构, 最后所形成的晶体尺寸有大幅度的减小, 而且其形貌和PEG臂的分子量密切相关. 可见AB2星型杂臂共聚物的结晶是先由GMS臂结晶形成小晶核, 然后再诱导PEG臂球晶的生长. 杂臂的引入对于控制星型多臂共聚物的晶形、晶貌具有重要意义.     

Self-assembly in transition metal complexes: structural characterization of a copper histamine nitrate [Cu(II)(him)2(NO3)2]

A new monomeric copper (II) complex with histamine (him), [Cu(II)(him)₂(No₃)₂], has been prepared by the reaction of Cu(NO₃)₂ with histaminium dichloride and its structure was determined by x-ray crystallography. The complex crystallizes in the triclinic system, space group with a = 5.7238(4), b = 8.7094(7), c = 9.2481(11) Å, = 69.693(8), = 73.242(7), = 71.050(7)°, V = 400.84(6) ų, and Z = 1. The structure consists of discrete [Cu(II)(him)₂(NO₃)₂] molecules in which the metal atom is centrosymmetrically coordinated by two histamine ligands forming an equatorial plane with Cu–N(imidazole ring) being 2.032(2) and Cu–N(NH₂ group) being 2.023(2) Å. Two O atoms from nitrate anions coordinate on the elongated axial positions with Cu–O being 2.549(2) Å. In the crystal structure, the molecules are organized by hydrogen bonds forming a two-dimensional network.     

通过自缩合乙烯基氧阴离子聚合制备超支化聚甲基丙烯酸羟丙酯

由甲基丙烯酸羟丙酯通过自缩合乙烯基氧阴离子聚合(self-condensing vinyl oxyanionic polymerization)制备了端羟基的超支化聚甲基丙烯酸酯. 以氢化钾(KH)和冠醚的复合物为引发剂时, 可以得到高分子量的聚合物. 用¹H NMR和¹³C NMR谱图证实了聚合物的超支化结构. 由于在聚合过程中存在质子转移反应, 引发剂与单体的摩尔比会影响所得聚合物的结构. 超支化聚合物的玻璃化转变温度在58.1～81.4 ℃之间, 且随着引发剂与单体的比例的减小而降低. 当引发剂与单体等摩尔比时, 所得聚合物的支化度为0.49.     

高度支化共聚物的均方回转半径和支化度的关系

对于聚合物的均方回转半径和支化度的关系, 过去鲜有定量研究, 这是由于具有不同支化度的系列同种聚合物样品较难合成之故. 1982年, Kricheldorf等[1]报道了AB2和AB型单体的共缩聚反应, 这种反应可以方便地通过调节AB2和AB型单体的比例来控制产物的支化度.     

超支化聚醚的支化度对玻璃化转变温度的影响

聚合物的分子结构对聚合物性能影响很大.支化度不同的同种聚合物,必须通过不同的催化体系合成,很难得到既具有相近分子量又具有不同支化度的系列聚合物样品,因此对聚合物性能与支化度的依赖关系的研究报道不多.     

ABg型缩聚形成的超支化聚合物的支化度与分子形态

用聚合反应动力学模型, 详细分析了AB_g型缩聚体系中各种结构单元的演变, 对超支化聚合物支化度的各种定义作了比较, 并对AB_g型反应体系的支化度提出了一个改进的定义, 使得支化度随g的增加而增加, 当g从2增加到无穷大, 最大支化度相应地从0.5增加到1－e^－1. 对均方回转半径的数值计算表明, 在确定的A基团转化率(x), z-均均方回转半径几乎与g无关, 当x＝0.999时, 随着g从2增加到无穷大, z-均回转半径只增加0.1%. 但是, 同样的条件下, z-均聚合度增加到2倍. 这一现象表明在任何指定的A转化率, AB_g型缩聚中形成的超支化聚合物的分子轮廓与g无关, 随着g 增大而在超支化聚合物中增加的结构单元(或聚合度)必定分布在分子内部.     

Synthesis,crystal structure and properties of a novel di-μ2-aqua bridged binuclear manganese(III) Schiff base complex [Mn(vanen)(H2O)2]2(ClO4)2 · 2H2O

The preparation and isolation of the binuclear manganese(III) complex, [Mn(vanen)(H₂O)₂]₂(ClO₄)₂ · 2H₂O was accomplished by air oxidation of a solution containing H₂vanen^**, Et₃N, and Mn(ClO₄)₂ · 6H₂O in absolute EtOH. The crystal structure of complex was determined by X-ray crystallography, and consists of two molecules bridged by two water molecules through hydrogen bonding. The manganese atom is six-coordinate and presents a distorted octahedral coordination sphere, which consists of the two imine N atoms and two phenolic O atoms of vanen^2– ligand in the equatorial plane, with Mn–N bond distances of 1.975 and 1.987 Å, and Mn–O distances of 1.867 and 1.876 Å, respectively. The non-bonding interatomic MnMn distance is 4.79 Å. In the axial direction, the elongated Mn–O(H₂O) bond distances of 2.255 and 2.381 Å, respectively, are due to Jahn–Teller distortion at the d⁴ metal center. The presence of lattice and coordinate water molecules were also confirmed by the t.g. study and the i.r. spectra. Upon irradiation using visible light in water in the presence of p-benzoquinone, the complex demonstrates its ability to split water.     

Crystal structure of [Cu2(II)(dmpa)2(p-Cl-C6H5COO)2] (Hdmpa = N,N-dimethyl-3-amino-1-propanol)

The copper complex, [Cu₂(II)(dmpa)₂(p-Cl-C₆H₅COO)₂], has been prepared and its structure determined using X-ray crystallography. The dimer is a di-₂-alkoxo complex which is a five-coordinate copper dimer with unsupported alkoxo bridges. The complex crystallizes in the triclinic space group P-1 with a = 11.384(2), b = 14.636(5), c = 9.609(2) Å, = 100.07(2), = 104.33(3), = 72.79(2)°, V = 1471.8(7) ų, and Z = 2. The structure is comprised of discrete binuclear clusters in which the metal atoms are bridged by two alkoxo oxygens of the dmpa^– ligands. The Cu-O and Cu-N distances are in good agreement with those found for other copper(II) aminoalcoholato complexes. The Cu···Cu distance is 2.9765(6) Å. In the crystal, every two dimeric coordination molecules are combined together by the recognition through intermolecular hydrogen-bonding interactions between the apical water molecule and the non-coordinated O atom from the p-chlorobenzoato ligand, forminga tetramer.     

原位傅里叶变换红外光谱跟踪等规聚丙烯在升温过程中的构象变化

自从 Natta[1]首次成功合成高分子量的等规聚丙烯 (i PP)以来 ,红外光谱就被广泛地应用于 i PP的组成和结构的表征[2～ 13] .1 988年 ,Hendra等[3] 采用逐步升温方法 ,静态观察 i PP红外光谱的构象规整谱带随温度的变化 ,发现当温度高于 1 35℃时 ,i PP分子链的活动性增加 ,样品的凝聚态结构发生了明显的变化 .然而 ,他们却未能找出产生这一现象的直接原因 .本文利用快速升温傅里叶变换红外光谱(FTIR)在线跟踪 i PP大分子在升温过程中的分子构象变化 ,并结合其它实验手段 ,阐明了上述现象来源于 i PP非晶区螺旋序列的无序化 .1　实…