Living radical polymerization of vinyl chloride initiated with iodoform and catalyzed by nascent Cu0/tris(2‐aminoethyl)amine or polyethyleneimine in water at 25 °C proceeds by a new competing pathways mechanism

The first example of living radical polymerization of vinyl chloride carried out in water at 25 °C is reported. This polymerization was initiated by iodoform and catalyzed by nascent Cu⁰ produced by the disproportionation of Cu^I in the presence of strongly Cu^II binding ligands such as tris(2‐aminoethyl)amine or polyethyleneimine. The resulting poly(vinyl chloride) was free of structural defects, had controlled molecular weight and narrow molecular weight distribution, contained two ～CHClI active chain ends, and had a higher syndiotacticity (62%) than the one obtained by conventional free‐radical polymerization at the same temperature (56%). This novel polymerization proceeds, most probably, by a combination of competitive pathways that involves activation by single electron transfer mediated by nascent Cu⁰ and degenerative chain transfer. © 2003 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 41: 3283–3299, 2003     

空间群O_h~7O~4T~2母分系数的计算

在群链G G_1 G_2中,把两个子群的IR(不可约表示)基相乘,然后把乘积基耦合成IR基,耦合系数我们称之为母分系数。本文把陈金全创立的本征函数法用于计算空间群的群链O_h~7 O~4 T~2的母分系数,计算的结果显示母分系数是满足正交关系,同时也说明此方法是适用的。     

The reversible addition‐fragmentation chain transfer process and the strength and limitations of modeling: Comment on “the magnitude of the fragmentation rate coefficient”

There is appreciable uncertainty concerning the magnitude of the fragmentation rate coefficient of the intermediate radical in reversible addition‐fragmentation chain transfer (RAFT) polymerizations. A large proportion of the experimental and theoretical evidence suggests that it is a stable species with a lifetime longer than 0.0001 s. This is particularly the case when the intermediate macro‐RAFT radical is stabilized by a phenyl group attached to the radical center or has a poor leaving group. Although the occurrence to some extent of irreversible termination reactions cannot be excluded, we argue that such reactions are more likely to be a result of slow fragmentation of the intermediate macro‐RAFT radical. © 2003 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 41: 2828–2832, 2003     

多重休假Mx/G/1排队系统的输出过程

本文首次研究服务员具有多重休假规则的成批到达Mx/G/1排队系统的输出过程.应用更新过程理论、拉普拉斯-司梯阶变换和本文提出的直接概率分解分析法,讨论了从任意初始状态出发,系统在(0,t]时间内输出顾客的平均数,以及其渐近展开,得到一些重要结果.     

双杂质一维原子链中的晶格振动

对于含有两个杂质的一维单原子链的振动方程求解,得到晶格振动频率的解.分析了振动频率和杂质质量以及两杂质间距离的关系.     

三角债的模糊矩阵表示和关系划转的数学模型

给出债务关系的模糊矩阵表示,用其幂运算判定间接债务关系存在性,最后给出债务关系划转的方法,可作为三角债分析和相关问题解决的技术工具.     

Self-assembly of Gold Nanoparticle Chains between Nanoelectrodes

Nanodevice applications of metal or semiconductor nanoparticles depend on the techniques to assemble them into ordered one-(1D) and two-dimensional (2D) arrange- ments1,2. In particular, 1D arrangements of nanoparticles are not only the basis for fabricat…     

反应挤出接枝共聚反应表观链增长常数的测量

以预辐照的LLDPE反应挤出接枝MAA作为研究对象，通过在双螺杆挤出机中的不同部位取样，用FFIR分析接枝物及均聚物的产量，并用ESR测试链增长自由基浓度，设计了测定接枝和均聚反应初始阶段的表观链增长常数的方法,结果表明，在本实验测试范围内表观接枝链增长常数不同于均聚链增长常数；所得的测量值符合理论预测值，证明测试方法适合高温熔融体系的研究。     

Transformation Operators for the Perturbed Hill Difference Equation and One of Their Applications

We construct transformation operators with conditions at infinity for the perturbed Hill equation. We give one application of transformation operators to studying solutions of some nonlinear difference equation.