锂在共轭双键高分子中的电化学嵌入反应III. 锂嵌入聚噻吩的量子化学计算†

采用Gaussian软件和HF方法, 通过从头计算(ab initio)法选取4-31G基组计算锂离子嵌入聚噻吩过程中结构与结合能的变化关系. 发现噻吩聚合时主要生成三或四聚合物. 聚合物在Li原子(或Li^＋离子)嵌入后, 聚噻吩间距离明显变小, 同时发生电荷转移, 形成稳定嵌合物; 并使噻吩环的C-α—C-β键级变小. 同时, 研究了锂离子(或原子)嵌入后体系的HOMO, LUMO能级. 聚噻吩在嵌入锂离子时LUMO轨道能级变为负值, 成为电池反应得电子的正极. 而金属Li₂ 释放Li^＋后的Li^－的HOMO能级为＋0.7427 eV, 则成为给电子的负极. 由此, 可以完成由锂/聚噻吩在高氯酸锂电解质中组成的放电过程, 并提出嵌合键级概念用来表征锂在聚噻吩间的结合程度.     

The Crystallization and Melting Behaviors of PDLA-b-PBS-b-PDLA Tri-block Copolymers

In this study,the poly(D-lactide)-block-poly(butylene succinate)-block-poly(D-lactide)(PDLA-b-PBS-b-PDLA)triblock copolymers with a fixed length of PBS and various lengths of PDLA are synthesized,and the crystallization behaviors of the PDLA and PBS blocks are investigated.Although both the crystallization behaviors of PBS and PDLA blocks depend on composition,they exhibit different variations.For the PDLA block,its crystallization behaviors are mainly influenced by temperature and block length.The crystallization signals of PDLA block appear in the B-D 2-2 specimen,and these signals get enhanced with PDLA block length.The crystallization rates tend to decrease with increasing PDLA block lendth during crystallizing at 90 and 100°C.Crystallizing at higher temperature,the crystallization rates increase at first and then decrease with block length.The crystallization rates decrease as elevating the crystallization temperature.The melting temperatures of PDLA blocks increase with block lengths and crystallization temperatures.For the PBS block,its crystallization behaviors are mainly controlled by the nucleation and confinement from PDLA block.The crystallization and melting enthalpies as well as the crystallization and melting temperatures of PBS block reduce as a longer PDLA block has been copolymerized,while the crystallization rates of the PBS block exhibit unique component dependence,and the highest rate is observed in the B-D 2-2 specimen.The Avrami exponent of PBS crystallites is reduced as a longer PDLA block is incorporated or the sample is crystallized at higher temperature.This investigation provides a convenient route to tune the crystallization behavior of PBS and PLA.     

Electrochemical intercalation reaction of lithium into sulfides of nonlayer structure: I. Lithium intercalation in lead sulfide

The reaction mechanism of cell Li/PbS has been studied with coulombic titration, cyclic voltammetry and X-ray diffraction methods. It was found that in the first stage of discharge (0< y ≤1.5), the intercalation of lithium into lead sulfide took place. The X-ray diffraction patterns showed that the main crystalline structure of PbS remained unchanged after lithiation, and the lithium intercalated probably locates in the center of the cubic-interspace of the crystal. The intercalation free energy of Li into PbS forming LiPbS was found to be ?300.48 KJ·mol^?1 (at 25°C). The chemical diffusion coefficient of lithium in Li_yPbS (0<y≤1) was determined by electrochemical method to be about 10^?11 cm²S-1.     

碳纳米纤维糊电极电化学发光法测定甲硫哒嗪

制备了基于碳纳米纤维糊电极(CFPE)的新型电化学发光传感器.运用电化学方法对CFPE进行了表征,并考察了三联毗啶钉和甲硫哒嗪在此电极上的电化学行为和电化学发光行为.结果表明,该电极表现出很好的电化学活性和电化学发光响应.基于甲硫哒嗪对三联吡啶钉电化学发光的增强作用,建立了测定甲硫哒嗪的电化学发光新方法.实验考察了缓冲...     

脉冲激光沉积LiMn2O4薄膜的研究

在氧气氛下采用355nm脉冲激光烧蚀制备了LiMn₂O₄薄膜,并用四极质谱和发光光谱技术考察了脉冲激光烧蚀过程及环境氧气对薄膜沉积过程的影响.质谱测定结果表明,355nm激光烧蚀LiMn₂O₄的产物主要有Li⁺、Mn⁺等离子和O₂、O、LiO₂、LiMnO、MnO及锂原子的多聚体等中性产物.不同氧气压下测定的发光光谱表明烧蚀原子在环境氧气氛中存在氧化过程.用循环伏安法和X射线衍射法对薄膜进行了表征.     

聚苯胺/碳纳米纤维复合材料的制备及电容性能

采用原位聚合法制备了聚苯胺/碳纳米纤维(PANI/CNF)复合材料,用傅里叶变换红外(FT-IR)光谱、热重分析(TGA)、扫描电镜(SEM)和孔分布及比表面积测定仪研究了复合材料的表面官能团、组成、表面形貌及比表面积,并运用循环伏安(CV)法和计时电位法测试了PANI/CNF布作为电极材料的电化学性能.研究结果表明:PANI/CNF复合材料具有粗糙的毛刺结构,PANI沿碳纳米纤维均匀分布;PANI/CNF电极氧化还原反应的可逆性良好;在100mA·g-1电流密度下,当PANI含量为44.4%(w)时,复合材料比电容量高达587.1F·g-1,比能量为66.1Wh·kg-1,电流密度为800mA·g-1时比功率可达1014.2W·kg-1;在5A·g-1的电流密度下,1000次循环充放电后,复合材料的比电容量衰减28%.PANI/CNF复合材料具有良好的导电性和快速充放电能力,是一种优良的超级电容器电极材料.     

可溶性聚酰亚胺的电化学行为

聚酚亚胺（PI）以其优良的热稳定性、化学稳定性和作为优良的绝缘材料而被广泛应用于电子工业'．Haushalt。了和Kra。l。e等Li发现I'I膜在一定条件下可进行电化学反应．PI由于在电沉积等方面有潜在的应用价值,现已有一些这方面的研究工作卜一'．但所用的材料都是不溶性的PI,且用不同的方法制备PI薄膜修饰电极,因此所报道的PI在水或非水溶液中的电化学行为各不相同［'－'j．另外,以往的研究大都用一种商品化的l'I,而没有系统地研究PI结构对电化学行为的影响．本文报道了由相同的二胺和不同的二欧经化学环化制备的5种可溶性PI…     

Theoretical Study on the Mechanism of Sonogashira Coupling Reaction

The mechanism of palladium-catalyzed Sonogashira cross-coupling reaction has been studied theoretically by DFT （density functional theory） calculations. The model system studied consists of Pd（PH3）2 as the starting catalyst complex, phenyl bromide as the substrate and acetylene as the terminal alkyne, without regarding to the co-catalyst and base. Mechanistically and energetically plausible catalytic cycles for the cross-coupling have been identified. The DFT analysis shows that the catalytic cycle occurs in three stages： oxidative addition of phenyl bromide to the palladium center, alkynylation of palladium（Ⅱ） intermediate, and reductive elimination to phenylacetylene. In the oxidative addition, the neutral and anionic pathways have been investigated, which could both give rise to cis-configured palladium（Ⅱ） diphosphine intermediate. Starting from the palladium（Ⅱ） diphosphine intermediate, the only identifiable pathway in alkynylation involves the dissociation of Br group and the formation of square-planar palladium（Ⅱ） intermediate, in which the phenyl and alkynyl groups are oriented cis to each other. Due to the close proximity of phenyl and alkynyl groups, the reductive elimination of phenylacetylene proceeds smoothly.     

High Strength and Stable Proton Exchange Membrane Based on Perfluorosulfonic Acid/Polybenzimidazole

In this work, a series of high strength, thermal stable and antioxidant proton exchange membranes were designed with solution processible polybenzimidazole(PBI) as the matrix and perfluorosulfonic acid(PFSA) as the fortifier for proton exchange. Solution processible PBI was successfully synthesized by introducing 4,4’-dicarboxydiphenyl ether into the molecular chains of PBI. PFSA/PBI composite membranes were obtained by solution blending and film casting. PBI and PFSA/PBI composite membranes exh...     

High Strength Electrospun Single Copolyacrylonitrile (coPAN) Nanofibers with Improved Molecular Orientation by Drawing

High-performance carbon nanofibers are highly dependent on the performance of their precursors, especially polyacrylonitrile (PAN).In this work, the copolymer of PAN (coPAN) was synthesized for electrospinning. A self-assembling set-up was used for the stretching of single coPAN nanofibers. FTIR and Raman spectroscopies were used to characterize the chemical structure of coPAN nanofibers. Scanning electron microscopy (SEM) and atomic force microscopy (AFM) were used to monitor the morphology of single coPAN nanofibers under different drawing times. Micro-tensile test was used to determine the mechanical properties of single coPAN nanofibers. The results indicated that the drawing led to an increase in degree of molecular orientation along the fiber axis from 0.656 to 0.808, tensile strength from 304 MPa to 595 MPa, and modulus from 3.1 GPa to 12.4 GPa. This research would provide fundamental information of high-performance electrospun coPAN nanofibers and offer opportunities for the preparation of high-performance carbon nanofibers.