CuCl2对聚乙二醇（PEG）的构象和结晶的影响

用傅里叶变换红外光谱法(FT-IR)、差示扫描量热法(DSC)、广角 X射线衍射法(WAXD)研究了少量过渡金属盐氯化铜(CuCl2)对聚乙二醇(PEG)构象和结晶行为的影响. Cu2＋与PEG分子链中的氧原子有配位键生成, 通过溶液电导率的测定, 发现一个Cu2＋大约与3个PEG链节单元形成配位结构, 从而使PEG的构象和结晶行为发生变化, 随着体系中CuCl2含量的增加, PEG分子链中OC—CO旁式构象相对反式构象含量逐渐增加, 在CuCl2含量(w)为7%左右时达到极大值, 在CuCl2含量(w)为9%时, 反而是反式构象相对旁式构象含量多些. 混合物中PEG的结晶度随着体系中CuCl2含量的增加逐渐降低, 含量(w)为9%时, 又有所提高.     

变温红外法研究聚对苯二甲酸乙二酯分子链的松弛运动及其构象转变

在30～170 ℃范围内逐渐升温过程中,用红外光谱仪原位检测无定形聚对苯二甲酸乙二酯（PET）薄膜红外光谱图的变化情况。通过特征谱带吸光度与温度的变化特点,研究了PET分子链在热变化过程中的松弛运动及冷结晶过程中分子链的构象变化。实验结果表明在冷结晶过程中,随PET结晶的不断完善,对应左右式(gauche)构象的吸收峰减弱,对应反式(trans)构象的吸收峰增强,并计算出CH2面外摇摆振动结晶前和结晶后反式构象和左右式构象的相对百分含量随温度的变化关系,以及玻璃化转变和冷结晶的温区范围。     

月桂胺盐酸晶体相变的红外光谱研究

在290-365K的温度区间内考察了月桂胺盐酸盐晶体红外光谱随温度的变化规律。结果表明:月桂胺盐酸盐在339K发生了固-固结构相变, 该相变的预相变起始点为327K。在327K以下的低温相中, 晶体中分子的碳氢链以高度有序的全反式构象存在, 极性头部的三个N-H-Cl氢键是不等价的。在327-339K的中间过渡相, 碳氢链中出现了旁式构象, 分子链间相互作用减弱。不等价的N-H-Cl氢键的差异减小。在339K以上的高温相中, 分子旁式链构象的增多导致了分子链横向堆积无序性的明显增加, 三个N-H-Cl氢键已变得等价。     

月桂胺盐酸晶体相变的红外光谱研究

在290-365K的温度区间内考察了月桂胺盐酸盐晶体红外光谱随温度的变化规律。结果表明:月桂胺盐酸盐在339K发生了固-固结构相变, 该相变的预相变起始点为327K。在327K以下的低温相中, 晶体中分子的碳氢链以高度有序的全反式构象存在, 极性头部的三个N-H-Cl氢键是不等价的。在327-339K的中间过渡相, 碳氢链中出现了旁式构象, 分子链间相互作用减弱。不等价的N-H-Cl氢键的差异减小。在339K以上的高温相中, 分子旁式链构象的增多导致了分子链横向堆积无序性的明显增加, 三个N-H-Cl氢键已变得等价。     

原位合成的Cu-SSZ-13催化剂：结晶时间对NH3-SCR性能的影响

通过一步法原位合成Cu-SSZ-13分子筛催化剂,考察了结晶反应时间对NH3选择性催化还原(NH3-SCR)催化性能的影响,利用H2程序升温还原(H2-TPR)、X射线衍射(XRD)、电子顺磁共振光谱(EPR)和X射线电子能谱(XPS)等分析手段表征催化剂。结果表明,结晶时间不同会影响到Cu-SSZ-13分子筛中活性Cu物种的含量和分布,结晶时间为4 d时Cu-SSZ-13分子筛的NH3-SCR催化性能最佳。高温水热条件下,Cu-SSZ-13分子筛中不稳定的Cu~(2+)A物种会发生迁移而形成相对稳定的Cu~(2+)B物种;Cu~(2+)物种发生团聚而造成分子筛结构破坏,部分Cu~(2+)物种也因分子筛骨架坍塌而被包埋,这是导致催化活性下降的主要原因。     

气相白炭黑/低分子量聚乙二醇悬浮体系的分子弛豫与流变行为

采用亲水气相二氧化硅(FS)、非缠结聚乙二醇(PEG,重均分子量400)制备悬浮体系,考察FS体积分数(φ)对PEG本体相α-松弛、结晶行为及悬浮体系流变行为的影响.结果表明,FS可延缓PEG本体相α-松弛,提高玻璃化转变温度,并显著增加浮体系黏度,降低本体PEG相结晶与熔融焓.低填充时,FS起成核作用;高填充时,FS延迟PEG分子扩散,并降低结晶温度.FS对PEG结晶的不同作用发生在悬浮体系溶胶-凝胶转变附近,此时悬浮液非线性动态流变行为呈现显著的硬化软化特性,线性动态流变行为呈现最为显著的频率依赖性.通过建立线性动态流变行为叠加曲线,揭示了FS对PEG分子链扩散行为的显著推迟作用.     

硬弹性聚丙烯晶相和非晶相分子链取向的研究

本文用力学-振动光谱研究了硬弹性聚丙烯(HEPP)晶区和非晶区分子链在拉伸时取向的变化.我们发现在红外光谱中,1130—1190cm~(-1)波数范围内存在着三个峰,其中1167cm~(-1)处的峰是与结晶相长螺旋分子链相关的构象谱带,其谱带的强弱变化是与998cm~(-1)结晶谱带在拉伸时的变化趋势一致的.1159cm~(-1)谱带能够被归属于无定形谱带.而1152cm~(-1)处的峰也许是与短螺旋分子链构象谱带相关的.我们用计算机的二次微分、解卷积以及分峰程序测定了拉伸时HEPP晶区和非晶区分子链的取向函数,结果发现HEPP无定形分子链取向随拉伸比增加而增加,而晶区分子链的取向随拉伸比的增加先下降,直至拉伸比为1.5(第二次屈服点)后才逐渐增加.     

变温傅里叶红外光谱技术研究硬脂酸C-H伸缩振动

采用傅里叶红外光谱技术研究了温度对于硬脂酸C-H伸缩振动、分子脂肪链构象改变和分子间作用力的影响。运用变温红外技术在293~393K范围内,分别测定了硬脂酸C-H的一维红外光谱、二阶导数红外光谱、四阶导数红外光谱和去卷积红外光谱。结果表明:1在293~333K范围内,一维红外光谱中2 965,2 870cm-1附近的弱吸收谱带分别归属于甲基的不对称伸缩振动模式νas(-CH3)和对称伸缩振动模式νs(-CH3),相应的导数光谱及去卷积红外光谱能提高一维红外谱的分辨率;2在293~333K范围内,硬脂酸脂肪链处于全反式构象,在348~353K范围内,硬脂酸分子脂肪链构象由全反式构象向无序构象转变;3随着测量温度的升高,硬脂酸分子间的作用力不断降低。     

高灵敏度二维光子晶体水凝胶Cu~(2+)传感器

以聚苯乙烯二维光子晶体阵列为模板,戊二醛为交联剂,制备了聚乙烯醇二维光子晶体水凝胶(PVA 2DPCH),再以巯基乙酸为酯化剂,通过聚乙烯醇(PVA)的巯基化改性,得到巯基化聚乙烯醇二维光子晶体水凝胶(PVA-SH 2DPCH).利用德拜环法,研究了PVA-SH 2DPCH对Cu~(2+)的响应行为.结果表明,PVA-SH 2DPCH对Cu~(2+)具有超灵敏响应,在Cu~(2+)溶液中,凝胶收缩,其德拜环直径(D)随Cu~(2+)浓度的增大而增大,当Cu~(2+)浓度由0增加至10-15 mol/L时,其德拜环直径即可增加0.45 cm,当浓度继续增大到10~(-7) mol/L时,其德拜环直径(ΔD)可增加0.85 cm.当Cu~(2+)浓度在10~(-15)～10~(-7) mol/L范围内时,PVA-SH2DPCH的德拜环直径变化(ΔD)与Cu~(2+)浓度(c)呈线性关系,其线性回归方程为ΔD=1.195+0.0493×logc,(ΔD, cm;c, mol/L),R~2=0.99899.以制备的PVA-SH 2DPCH为Cu~(2+)传感器,利用德拜环法表征溶液中Cu~(2+)的浓度,方法简单快速兼具无标记、可视化检测的特点,为现场实时检测Cu~(2+)提供了可能.     

一步水热合成Cu-SAPO-34选择性催化丙烯还原氮氧化物（英文）

采用一步法水热合成不同Cu/Al比的Cu-SAPO-34催化剂,并对其丙烯选择性催化还原NO(C3H6-SCR)性能进行了研究。通过N2吸附-脱附、X射线衍射(XRD)、X射线光电子能谱(XPS)、程序升温还原(H2-TPR)和原位漫反射傅里叶变换红外光谱(In situ DRIFTS)等研究手段对催化剂进行表征,考察Cu-SAPO-34中Cu物种含量对催化剂的物理化学性质和反应活性的影响。结果表明,当铜负载量为2.76%～4.12%(w/w)时,Cu-SAPO-34催化剂在富氧条件下300～400℃内表现出非常有吸引力的C_3H_6-SCR活性,可实现～100%的脱硝效率和～100%的N_2选择性。原位红外光谱研究表明,Cu-SAPO-34分子筛骨架上孤立的Cu~(2+)离子是NO吸附和活化形成NO_2~-/NO_3~-中间物种的主要活性位,并通过C_3H_6-SCR反应过程中Cu~(2+)/Cu~+氧化还原循环来实现Cu~(2+)离子的持续供给。     

Structural and conformational changes during thermally‐induced crystallization of poly(trimethylene terephthalate) by infrared spectroscopy

Conformational changes occurring during thermally‐induced crystallization of poly(trimethylene terephthalate) (PTT) by annealing have been studied using density measurement, differential scanning calorimetry (DSC), and mid‐infrared spectroscopy (MIR). Infrared spectra of amorphous and semicrystalline PTT were obtained, and digital subtraction of the amorphous contribution from the semicrystalline PTT spectra provided characteristic MIR spectra of amorphous and crystalline PTT. The normalized absorbance of 1577, 1173, and 976 cm^?1 were plotted against the crystallinity showing that these bands can be used unambiguously to represent the trans conformation while the band at 1358 cm^?1 can be used to represent gauche conformation of methylene segment. The presence of a weak band at 1358 cm^?1 in the amorphous spectrum suggested that a small amount of gauche conformation is present in the amorphous phase. Infrared spectroscopy has been used for the first time as a means to estimate the trans and gauche conformations of methylene segments in PTT as a function of T_a. The amount of gauche conformation was plotted against the crystalline fraction and the extrapolation of this plot to zero crystalline fraction provided a value of 0.07, suggested that the pure amorphous phase consist of ～ 7% gauche conformation. It was found that the amorphous and crystalline gauche conformation increases at the expense of amorphous trans conformation during thermally induced crystallization of PTT. © 2008 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 46: 1497–1504, 2008     

Poly(ethylene terephthalate) copolymers containing nitroterephthalic units. II. Crystallization and conformational studies

The effect of incorporating a nitro side group into the phenylene units of poly(ethylene terephthalate) (PET) on the conformation and crystallizability of this polyester was evaluated. Random poly(ethylene terephthalate‐co‐nitroterephthalate) (PETNT) copolymers containing 5, 10, and 15 mol % nitroterephthalic units were investigated with reference to PET. All the examined copolymers were semicrystalline and were found to adopt the triclinic crystal structure of PET, with the nitrated units being excluded from the crystallites. Both the crystallinity and crystallization rate of PETNT largely decreased with the content of nitrated units, and the O? CH₂? CH₂? O trans‐to‐gauche conformational ratio increased with crystallization, attaining comparable values for all the compositions. The conformation and crystallinity of isothermally crystallized PET and PETNT samples could be correlated with the size of the crystallites generated in each case. However, a different crystal perfecting mechanism seemed to operate for PET and for the PETNT copolymers when they were subjected to annealing. © 2002 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 40: 2759–2771, 2002     

Oxygen‐barrier properties of cold‐crystallized and melt‐crystallized poly(ethylene terephthalate‐co‐4,4′‐bibenzoate)

This study examined the oxygen‐transport properties of poly(ethylene terephthalate‐co‐bibenzoate) (PETBB55) crystallized from the melt (melt crystallization) or quenched to glass and subsequently isothermally crystallized by heating above the glass‐transition temperature (cold crystallization). The gauche–trans conformation of the glycol linkage was determined by infrared analysis, and the crystalline morphology was examined by atomic force microscopy. Oxygen solubility decreased linearly with volume fraction crystallinity. For melt‐crystallized PETBB55, extrapolation to zero solubility corresponded to an impermeable crystal with 100% trans glycol conformations, a density of 1.396 g cm^?3, and a heat of melting of 83 J g^?1. From the melt, PETBB55 crystallized as space‐filling spherulites with loosely organized lamellae and pronounced secondary crystallization. The morphological observations provided a structural model for permeability consisting of impermeable platelets randomly dispersed in a permeable matrix. In contrast, cold‐crystallized PETBB55 retained the granular texture of the quenched polymer despite the high level of crystallinity, as measured by the density and heat of melting. Oxygen solubility decreased linearly with volume fraction crystallinity, but zero solubility corresponded to an impermeable defective crystal with a trans fraction of 0.83 and a density of 1.381 g cm^?3. © 2002 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 40: 2489–2503, 2002     

Structural relaxation in amorphous 1,2-dichloroethane studied by transformation between conformation isomers

Structural relaxation in amorphous 1,2-dichloroethane (DCE) samples prepared by vapor deposition on cold substrates were studied by Raman scattering. The gauche and trans molecules of DCE were found to coexist in amorphous states immediately after the deposition, and structural relaxation occurred with temperature elevation before crystallization. Mole fraction of the gauche isomer increased during this relaxation process, although trans is the stable isomer in gaseous and crystalline states. At the final amorphous stage immediately before crystallization, the gauche mole fraction was close to the mole fraction of the supercooled liquid state. It was also found that trans molecules located at positions with lower density were more easily transformed into the gauche conformation, while the distribution of the local structure around the resultant gauche molecules remained almost unchanged during the structural relaxation. Such behaviors of amorphous DCE are discussed from the viewpoint of the characteristic molecular structure of DCE.     

Conformational supramolecular isomerism in one-dimensional silver(I) coordination polymer of a flexible bis(bidentate) N,N-donor ligand with p-xylyl spacer

The isolation and structural characterisation of three isomeric silver(I) complexes, 1a, 1b and 2 with the general formula {[AgL(1)]ClO(4)}(n) (where L(1) is a bis(bidentate) N,N-donor ligand derived from the Schiff-base condensation of α,α'-diamino-p-xylene and pyridine-2-carboxaldehyde) are discussed. Single-crystal X-ray structures reveal the polymeric nature for the complexes where all the silver ions are in pseudotetrahedral geometry with the AgN(4) coordination environment. Isomers 1a (Pc space group) and 1b (Cc space group) were crystallised from acetonitrile whereas 2 (C2/c space group) was crystallised during the synthesis from a solvent mixture of dicholormethane and methanol. The flexible ligand (L(1)) adopts only an anti conformation in 1b and the presence of two different anti conformations in the repeating unit results in the formation of a trapezoidal wave polymeric chain. However, both gauche and anti conformations of the ligand are found to be present in the polymeric chains of 1a. In the polymeric chain of 2, only one anti isomer of the ligand is present in the repeating unit resulting in a triangular wave chain. The structure of isomer 1a is solvent induced and solvent plays a major role in the crystal packing of this isomer. One-dimensional coordination polymers 1a, 1b and 2 are related to each other as conformational supramolecular isomers. Additionally, two independent polymeric chains parallel to each other: one triangular wave consisting of only an anti conformation and a trapezoidal wave chain consisting of alternate gauche and anti conformations of the ligand are observed in 1a. This is a rare example of two supramolecular isomers present in the same crystal. Six different conformers of the flexible ligand are observed in the crystals of coordination polymers.     

聚氧乙烯超薄膜中构象变化的红外光谱研究

近年来 ,有关聚合物薄膜的研究受到了广泛关注 .低维数高分子超薄膜的各种行为由于涉及到高分子运动的动力学、热力学本质而逐渐成为高分子科学研究中的一大热点 .实验结果表明[1～ 3] ,几何受限条件和基板对于聚合物薄膜结晶的形态及性能都会产生显著影响 .广角 X射线衍射实验和自由表面的掠入射 X射线实验 [4 ]表明 ,有些在本体中呈现液晶有序的聚酰亚胺在靠近基板附近变得更加有序 .Despotopoulou等 [5] 对聚二正己基硅烷在超薄膜中构象扰动的观察发现 ,当膜厚小于 2 0 0 nm时 ,聚二正己基硅烷的侧链变得无序 ,傅里叶变换红外光谱测试…     

Conformation of drawn poly(trimethylene terephthalate) studied by solid-state 13C NMR

The change in the conformation of the flexible O-CH2-CH2-CH2-O segment of poly(trimethylene terephthalate) (PTT) monofilament caused by drawing was investigated by means of the gamma-gauche effect on the 13C solid-state NMR chemical shift of the internal methylene carbon, combined with the NMR relaxations. The conformation around the O-CH2 and CH2-O bonds for as-spun fiber was trans/trans. On drawing, followed by heat treatment, the conformation changed to gauche/gauche. The ratio of gauche/gauche to trans/trans for the drawn PTT fiber was determined quantitatively.     

浓度及冷冻-解冻处理对CuCl_2水溶液中Cu~(2+)区域结构的影响

应用扩展X射线吸收精细结构(EXAFS)光谱研究了CuCl2水溶液中Cu2+的区域环境结构,通过测定CuCl2水溶液在不同浓度条件下及冷冻-解冻(FT)处理前后CuK边EXAFS吸收谱,研究了浓度及冷冻-解冻处理对Cu2+第一配位层结构的影响.EXAFS实验结果表明,CuCl2水溶液中Cu2+第一配位层距离中心原子Cu最近邻原子为O原子,配位数介于3.0-4.3之间,Cu—O键长在0.192-0.198nm之间,这种结构与Cu2+的Jahn-Teller效应有关.不同浓度的CuCl2水溶液中Cu2+的区域环境结构有很大不同,随着CuCl2水溶液浓度的升高,Cu2+第一配位层配位数减小,Cu—O键伸长.结构参数拟合结果证实冷冻-解冻处理对Cu2+的区域环境结构有影响,CuCl2溶液经冷冻-解冻处理后,Cu2+第一配位层配位数变大,热无序度增加.