非线型缩聚物的重均分子量

本文用数学期望方法研究了非线型共缩聚物的重均分子量,并推导出重均分子量表达式,将3种特例的理论曲线与实验结果相比较,两者基本相符。     

线型缩聚反应的计算机模拟

缩聚反应是一类重要的高分子合成方法。其中最简单的反应为线型缩聚体系,它可分为两类,分别是含有两个可缩合的官能团的单体或单体对进行的相互缩合的体系。Flory在上世纪四十年代采用统计方法对该缩聚体系做过系统的理论研究,并在官能团等活性的假定下提出了著名的Flory分布函数,由此揭示了反应体系中数均聚合度xn、重均聚合度xw、不同聚合度分子的分布情况与反应程度p的关系。本文利用计算机模拟的方法,同样在官能团等活性的假定下模拟了线性缩聚反应的全反应过程,所得到的结果与用统计方法所得到的结果完全一致。本方法是对整个真实反应过程的直观模拟,对研究相似的以逐步聚合反应机理进行的反应具有普适性,并具有可拓展到模拟更真实的粘性聚合体系以及研究反应动力学的潜力。     

邻苯二甲酸酐与季戊四醇缩聚反应模型的统计处理

首次用统计方法对邻苯二甲酸酐与季戊四醇缩聚反应进了严格处理，获得了缩聚物的数量分布和重量分布函数，数均和重均分子量的表达式。同时还用环形处理法获得了邻苯二甲酸酐与季戊四醇缩聚反应的凝胶化条件。     

聚西夫碱型共轭高分子的合成及电性能的研究

从乙二醛、对苯二醛与二元胺反应得到八种线型共轭结构的缩聚物。在模型化合物及其对应的聚合物的紫外、可见吸收光谱显示出随分子共轭程度的增加向长波位移。乙二醛与对苯二胺的缩聚物热处理后使结构芳香化,而对苯二醛与对苯二胺缩聚物在350℃以下热处理时,仍发生进一步缩聚反应。缩聚物的导电性能与分子的共轭程度及分子间的结构有关。     

AB分批投入的A_r,AB型缩聚产物的分子量分布

本文用统计方法和动力学方法同时获得了AB单体分批投入的A_r,AB型缩聚产物的分子量分布函数和臂长的分布函数.由本文所提出的方法得到的产物的分子量分布远比AB一次投入的要窄.计算所得的结果与Monte Carlo模拟的结果完全符合.     

含水杨酸的缩聚物对P-硝基苯酚乙酸酯水解反应的催化作用(Ⅱ)

水杨酸、甲醛和烷基伯胺(烷基:甲基,正-丙基,正-己基或正-十二烷基)通过Mannich缩合反应制得了主链上既含有水杨酸基又含有叔胺基的线型缩聚物。用这些缩聚物催化P-硝基苯酚乙酸酯(PNPA)水解反应的动力学研究结果表明,缩聚物的催化活性随N-烷基侧链的链长增加而增加。在催化剂过量的条件下,带有十二碳烷基侧链的缩聚物催化PNPA水解反应时符合简单的Michaelis-Menten动力学历程。     

简单共聚模型的分布函数与组成方程推导

针对自由基共聚合反应歧化终止和偶合终止两类机理生成的线型共聚物,应用统计物理的基本原理,对处于最可几分布状态下的线型共聚物分子量分布函数进行了理论推导,并以此分布函数,结合自由基共聚合机理动力学处理和概率计算,从另一种途径得到Mayo-Lowis和Alfrey-Goldfinger简单共聚物组成方程,研究结果有助于进一步理解简单共聚模型组成方程的物理学基础,同时也将为线型自由基共聚合反应机理的研究提供一个新方法.     

缩聚理论对铝酸盐和硼酸盐系的应用

应用Folry的缩聚理论处理铝酸盐型熔体(MO-Al₂O₃),得到了聚合阴离子的分布函数。通过缩聚反应平衡常数可将混合自由能和组元活度表达为熔体组成的函数。预期了产生凝胶化的条件。由模型所得理论曲线与实验结果进行了比较。     

AB分批投入的AB,B型缩聚产物的分子量分布

本文用统计方法和动力学方法同时获得了AB单体分批投入的AB,B线型缩聚产物的分子量分布函数。所得的分子量分布远比Flory分布窄。计算结果与Monte Carlo模拟的结果完全相符合。     

单官能团单体C存在下A_2-B_2型缩聚产物的分子量分布

分别以概率统计方法和Monte Carlo模拟获得了单官能团单体C存在下A_2-B_2型线型缩聚产物的分子量分布。Monte Carlo方法与统计计算得出一致的结果,表明建立的Monte Carlo模型是合理的。研究了单官能团单体C的反应活性对缩聚产物分子量分布的影响,对反应体系中存在的各种不同的分子类型的消长情况分别进行了动态模拟。     

分子组装机器：纳米工厂

Molecular machines have attracted significant attentions as one of the most promising aspects of chemistry for their potential applications ever since receiving the 2016 Nobel Prize in Chemistry. The molecular assembler, also called the nanofactory, is a novel type of molecular machines that are capable of controlling the chemical reactions precisely at the microscopic level. As an analog to the macroscopic factories, nanofactories are comprised of a "transporting" part, the molecular walkers, and an "assembling" part, the molecular robotic arms. In this review, we provide a brief introduction of the research progress in recent years together with analysis on the principles of designing, constructing and operating molecular assemblers. We also summarize the prospects and challenges in the research area of molecular assemblers.     

外电场作用下寡聚苯分子导线的性质

利用Hartree-Fock 方法在6-31G*水平上对聚苯分子进行了计算研究. 分别从几何构型、分子轨道空间分布和分子轨道能级三个方面讨论了外电场对寡聚苯分子导线的影响, 给出了分子导线的性质与外电场的关系. 进一步, 连接硫原子于聚苯分子的两端, 并共价结合在金电极上. 利用非平衡格林函数方法对其在0-2.0 V 偏压下电子输运特征进行了深入研究.     

Dithienylethene-Based Single Molecular Photothermal Linear Actuator

By employing a mechanically controllable break junction technique, we have realized an ideal single molecular linear actuator based on dithienylethene (DTE) based molecular architecture, which undergoes reversible photothermal isomerization when subjected to UV irradiation under ambient conditions. As a result, open form (compressed, UV OFF) and closed form (elongated, UV ON) of dithienylethene-based molecular junctions are achieved. Interestingly, the mechanical actuation is achieved without changing the conductance of the molecular junction around the Fermi level over several cycles, which is an essential property required for an ideal single molecular actuator. Our study demonstrates a unique example of achieving a perfect balance between tunneling width and barrier height change upon photothermal isomerization, resulting in no change in conductance but a change in the molecular length, which results in mechanical actuation at the single molecular level.     

The atom assignment problem in automated de novo drug design. 5. Tests for envelope-directed fragment placement based on molecular similarity

Summary The fragment placement method has been successfully extended to the problem of envelope-directed design. The atom assignment paradigm was based on molecular similarity between two molecular structures. A composite supersurface is defined to form the surface onto which the molecular fields are projected. The assignment process is then determined by using molecular similarity in the objective function to be optimized. In principle, this procedure is closely similar to that outlined in the previous paper for site-directed design. The rationale has been extensively tested on two benzodiazepine antagonists believed to bind to the same site.     

I/V characteristics of a molecular switch

We present a study of the conduction properties of a class of aromatic compounds, whose conformation can be modulated with a transverse electric field, with strong effects on the molecular transport properties. The theoretical method includes the molecule–electrode interaction in a simple, although effective way: the coupling matrix elements are considered independent from the energy of the continuum spectrum of the lead. This results in a simple expression for the molecular Green’s function with a significant simplification in the expression of the transmission function. The effects of the voltage bias on the electronic molecular density is included through a uniform effective electric field. A simplified but accurate method for the evaluation of the molecular response to the field, which spares lengthy computations for each value of the voltage, is presented. The proposed method is calibrated on the widely studied benzene-1,4-dithiol molecule. The calculations on the selected molecular wire (a tetracyano derivative of 4,4′-di(mercaptoethynyl)tolan) show that conductivity is low for perpendicular rings, whereas conduction is allowed for the planar conformation, which corresponds to the equilibrium geometry in the absence of the transverse electric field.     

卟啉超分子化合物在分子器件中的应用

分子电子器件已成为近年来的一个研究热点，卟啉类化合物因为光敏性好、性能稳定、易于修饰等优点成为分子器件研究的理想模型化合物。本文着重介绍了它在分子器件中的最新应用进展。     

The atom assignment problem in automated de novo drug design. 2. A method for molecular graph and fragment perception

Summary If atom assignment onto 3D molecular graphs is to be optimized, an efficient scheme for placement must be developed. The strategy adopted in this paper is to analyze the molecular graphs in terms of cyclical and non-cyclical nodes; the latter are further divided into terminal and non-terminal nodes. Molecular fragments, from a fragments database, are described in a similar way. A canonical numbering scheme for the fragments and the local subgraph of the molecular graph enables fragments to be placed efficiently onto the molecular graph. Further optimization is achieved by placing similar fragments into bins using a hashing scheme based on the canonical numbering. The graph perception algorithm is illustrated in detail.     

分子纳米磁体的研究进展及应用

分子磁学主要研究无机配合物以及有机自由基的电子结构和磁性之间的关系。近些年发展起来的分子纳米磁体可以在单分子尺度上实现磁双稳态,独立作为一个磁功能单元,可能突破尺寸对传统磁性材料的制约,有望实现超高密度磁存储。分子纳米磁体中清晰的量子态也为量子退相干研究提供了化学调控的手段,这将为量子计算机提供物质基础。本文简要介绍了分子纳米磁体的概念和特征,并对研究进展进行了简要综述。     

二苯乙炔分子导线的电子输运性质

利用第一性原理非平衡态格林函数方法研究了不同构象下二苯乙炔分子导线的电子输运性质. 从分子轨道空间分布和透射谱等方面讨论了外加偏压下分子构象对电子传递特性的影响及内在机理. 结果表明, 随着分子扭转角的增加, 分子的LUMO-HOMO能隙增加, 透射峰显著降低; 外加偏压下, 分子的HOMO分布向低电势端移动, LUMO向高电势端移动. 电流-电压计算表明, 平面构象分子的导电性最好; 随着扭转角的增加, 分子的导电性变差; 垂直构象分子的导电性最差. 最后给出了分子导线电子传递性质与分子构象的定量关系.