蓖麻油聚氨酯／乙烯类聚合物交联共聚物的动态力学性能

本文研究了蓖麻油聚氨酯(COPU)/聚甲基丙烯酸丁酯(PBMA)交联共聚物(简称ABCP)的动态力学性能,并将其与COPU/PBMA,IPN的动态力学性能作了比较。发现在ABCP中两组份的阻尼峰互相叠加,形成半相容体系,而在IPN中阻尼峰有个宽的平台。透射电镜照片表明,IPN具有更大的相区结构。这些结果证明,化学交联比物理缠结具有更大的强迫互容性。通过对COPU/乙烯类聚合物(VP)交联共聚物相容性的研究,可知COPU/PBMA,COPU/PST和COPU/PMMA交联共聚物,在动态力学性能上是半相容体系,而COPU/PMA和COPU/PBA交联共聚物是互容体系。     

The Aharonov–Bohm effect in scattering theory

The Aharonov–Bohm effect is considered as a scattering event with nonrelativistic charged particles of the wavelength which is less than the transverse size of an impenetrable magnetic vortex. The quasiclassical WKB method is shown to be efficient in solving this scattering problem. We find that the scattering cross section consists of two terms, one describing the classical phenomenon of elastic reflection and another one describing the quantum phenomenon of diffraction; the Aharonov–Bohm effect is manifested as a fringe shift in the diffraction pattern. Both the classical and the quantum phenomena are independent of the choice of a boundary condition at the vortex edge, providing that probability is conserved. We show that a propagation of charged particles can be controlled by altering the flux of a magnetic vortex placed on their way.     

固体高分辨NMR研究PPU/PMAs,AB-交联聚合物中的分子运动和相容性

本文使用固体高分辨NMR测量了PPU/PMAs,AB-交联聚合物中PPU的侧甲基的¹³C自旋-晶格弛豫时间(T₁)。使用内旋转运动的平均谱密度函数分析了PPU侧甲基的内旋转和PMA的侧基的多重内旋转运动。结果表明PMA中的侧基距主链越远,其旋转速度越快并且PPU侧甲基的内旋转速度随ABCP中PMA侧链长度增加而变快。还使用质子的T_1ρ和T₂及自旋扩散研究了体系的相容性和相行为。得到了有关相应尺度下的每相的组成和软相微区尺度的信息。     

Thermotropic liquid‐crystalline polyesters containing biphenyl mesogens in the main chain: The effect of connectivity

A homologous series of main‐chain thermotropic liquid‐crystalline polyesters containing rigid biphenyl mesogen and flexible methylene spacers were synthesized with the AB‐type self‐polycondensation approach. The polyesters were characterized with ¹H NMR, gel permeation chromatography, thermogravimetric analysis, differential scanning calorimetry, polarized light optical microscopy, and X‐ray diffraction. These polyesters, containing trimethylene spacers on the acid side and various spacers on the alcohol side of the biphenyl mesogen, showed an odd–even effect in the transition temperatures and mesophase type. The even members showed higher transition temperatures than the odd ones. A normal smectic mesophase was observed for the even members, whereas the odd‐membered counterparts exhibited a tilted smectic mesophase. To study the effect of connectivity, the mesophase characteristics of these polyesters were compared with those of the isomeric AB‐type polyesters without any methylene spacer on the acid side of the biphenyl moiety. The mesophase characteristics were insensitive to whether the mesogen was connected to a carboxyl unit or a methylene unit. © 2004 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 42: 2734–2746, 2004     

快充MH-Ni电池AB3型负极合金与隔膜相互匹配的研究

（ML0.70Mg0．12Zr0．07Gd0．05MY0．06）Ni2.87Al0.08Co0.15是具有快速充电能力的AB3型负极合金材料，将此负极合金与正极以及尼龙或聚丙烯隔膜组成的快充形MH-Ni电池，研究了负极合金与隔膜的相互匹配性。结果表明：用交联型聚丙烯酸盐对隔膜改性生成的聚丙烯隔膜与该AB3型负极合金有良好的匹配性。     

绝热式热动力学的研究I:可逆反应动力学的数学模型

本文提出了几类可逆反应通用的微分动力学方程.并应用无量纲参数法,建立了可逆反应动力学的数学模型.还给出了一个解析实例.     

阳离子－π体系相互作用的理论研究 3: 碱金属阳离子－苯 复合物体系的量子 化学研究

运用abinitioHartree-Fock从头算,微扰MP2和密度泛函B3LYP方法在不同的基组水平上对碱金属阳离子－苯复合物体系的可能构型进行了自由优化,得到了复合物的能量最低构型为碱金属阳离子位于苯环平面的正上方,频率计算结果表明该结构为稳定结构.复合物的键长、原子净电荷、分子轨道、前沿轨道能量、Mullicken键级等都表明,碱金属阳离子和苯环碳原子之间的作用包含p-π作用方式,碱金属阳离子与苯结合时电子从苯环向碱金属阳离子转移,形成电荷转移复合物.它们之间的结合方式和氢键的结合方式相似,但计算得到的热力学参数表明复合物中碱金属阳离子与苯之间的结合强度远远大于典型的氢键,尤其是锂离子－苯复合物的生成焓已和普通的化学键相当.复合物的红外特征振动频率位于200^-^1附近,对应于碱金属阳离子垂直于苯环平面的来回振动,同时形成复合物后,原来位于3200cm^-^1的苯的C--H振动红外活性消失。     

钼铁硫原子簇化合物的结构规则

本文将过渡金属原子簇化合物的9N-L结构规则, 用于讨论Mo-Fe-S原子簇化合物, 得到了它们的结构和自旋性质之间的关系,推得的理论最大自旋值与实验事实吻合. 进而, 对各种Mo-Fe-S原子簇化合物的典型分子或模型分子, 进行了EHMO量子化学计算, 得到了与上述讨论相一致的结果, 进 一步揭示和验证了上述讨论的本质.     

Echo-time independent signal modulations using PRESS sequences: a new approach to spectral editing of strongly coupled AB spin systems

In clinical MR spectroscopy, double spin-echo point resolved spectroscopy (PRESS) sequences are routinely used for volume selection. For strongly coupled AB spin systems under PRESS excitation, the dependence of the signal on the echo time TE has been thoroughly investigated, whereas less attention has been paid to the signal modulation which occurs at constant TE with varying interpulse delays. A substantial TE-independent J modulation is here predicted from analytical solutions of the Liouville equation and density matrix simulations, and verified with experiments on citrate at 1.5 and 3T. It is also shown that this modulation effect could be exploited for editing of strongly coupled AB resonances or for removal of singlets in spectra-by means of difference spectroscopy-just using a standard PRESS sequence. The applicability in vivo of this new spectral editing approach is also demonstrated, with selective detection of citrate resonances in the human prostate. This novel approach has the advantages of being simple, and directly applicable on standard clinical MR scanners, provided that the exact behavior of the resonance is known.     

Synthesis and characterization of novel hyperbranched polybenzimidazoles based on an AB2 monomer containing four amino groups and one carboxylic group

A new kind of AB₂ monomer, 4‐[2,6‐bis(3,4‐diaminophenyl)pyridin‐4‐yl]benzoic acid, was synthesized, and several hyperbranched polybenzimidazoles (HPBIs) were prepared through self‐polymerization followed by modification reactions with end‐capping reagents such as 4‐methyl benzoic acid and 3‐[3,5‐bis(trifluoromethyl)phenoxy] benzoic acid. The HPBIs had good solubility in strongly aprotic solvents, such as N‐methyl‐2‐pyrrolidone, N,N′‐dimethylformamide, N,N′‐dimethylacetamide, and dimethyl sulfoxide. They also exhibited excellent thermal properties, with glass‐transition temperatures of 318–381 °C and 10% weight loss in the range of 338–674 °C in nitrogen and 329–509 °C in air. © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 5729–5739, 2006