Switchable Reversible Addition–Fragmentation Chain Transfer (RAFT) Polymerization with the Assistance of Azobenzenes

Modulating controlled radical polymerization is an interesting and important issue. Herein, modulating RAFT polymerization employing photosensitive azobenzenes is achieved. In the presence of azobenzenes and with visible light off, RAFT polymerization runs smoothly and follows a pseudo‐first‐order kinetics. In contrast, with light on, RAFT polymerization is greatly decelerated or quenched depending on the type and concentration of azobenzenes. Switchable RAFT polymerization of different (meth)acrylate monomers alternatively with light off and on is demonstrated. A mechanism of photoregulating RAFT polymerization involving radical quenching by azobenzenes is proposed.     

The effect of MWCNTs on molar mass in in situ polymerization of styrene and methyl methacrylate

Two different in situ-polymerization techniques were studied, emulsion polymerization and combined emulsion/suspension polymerization, with styrene and methyl methacrylate in the presence of different multiwalled carbon nanotubes (MWCNTs). Molar masses and molar mass distributions were determined by size exclusion chromatography, and particle size of the emulsions by dynamic light scattering and rotation rheometry. The compatibility of the MWCNTs and monomer affected polymerization and therefore the molar masses. The MWCNTs stabilized the emulsions, and molar mass distributions narrowed with higher amounts of MWCNTs. In emulsion polymerization of styrene, MWCNTs increased the molar mass. The increase of molar mass was based on the compatible molecular structures of MWCNTs and styrene, so that individual nanotubes were covered by monomer clouds when initiator arrived. In combined emulsion/suspension polymerization of styrene, MWCNTs reacted with the initiator and there was less initiator to polymerize the monomer. There is probably a critical surface area of MWCNTs, for which more initiator is consumed in the reaction with MWCNTs than in polymerization of the monomer. In emulsion polymerization of MMA, monomer clouds around MWCNTs do not form due to incompatible molecular structures, and nanotubes do not enhance polymerization of MMA. In combined polymerization, the initiator is reacting with the nanotubes and the tube is acting as a carrier for initiator, and molar masses are higher.     

原子转移自由基聚合与高分子构筑

活性聚合反应是目前高分子合成研究最为活跃的领域之一，原子转移自由基聚合反应（ATRP）是实现活性聚合的一种有效途径，可实现多种单体的活性聚合和可控自由基聚合。本文介绍了原子转移自由基聚合反应机理，重点综述了原子转移自由基聚合在高分子合成中的应用。     

醋酸乙烯(VAc)的活性/可控自由基聚合

本文综述了醋酸乙烯(VAc)单体的活性/可控自由基聚合研究进展.醋酸乙烯是一种重要的单体,是生产聚醋酸乙烯(PVAc)和聚乙烯醇(PVA)的原料.传统的自由基聚合方法如溶液、乳液、悬浮和分散等都可以用来实现VAc的聚合,得到不同分子量的PVAc和PVA.由于醋酸乙烯增长自由基的高活性,存在向聚合物链的链转移从而导致聚合物的分子量分布比较宽,为了得到分子量分布更窄的聚合物,活性可控聚合方法也被用来实现VAc的聚合.     

悬浮聚合法制备罗丹明B磁性分子印迹微球及其性能

以罗丹明B（RhB）为模板分子,采用悬浮聚合法制备了罗丹明B磁性印迹微球（M-MIPs）,对其进行了结构表征,并与本体聚合的印迹材料进行了对比。 结果表明,2种聚合物中的Fe3O4均呈现良好的晶形。 悬浮法制得的M-MIPs呈球形,粒径在50 μm左右,其饱和磁化强度(5.406 emu/g)比本体法制得的M-MIP（1.772 emu/g）更大,有利于快速磁性分离。 悬浮法所得M-MIPs的吸附量是本体法所得M-MIPs吸附量的近1.8倍,且在吸附速率、选择性、重复使用性能等方面,均明显优于后者。 2种材料均符合Langmuir吸附模型;悬浮法所得M-MIPs对RhB的吸附过程更符合二级动力学方程,而本体法所得M-MIPs较符合一级动力学方程。 悬浮法制得的M-MIPs更适合于RhB的识别、富集与分析应用。     

New Approaches to Synthesizing Electroactive Polymers

The chemical oxidative polymerization of aniline in a heterophase system is studied. In the presence of a solid substrate, the aniline polymerization involves two kinetically and chemically independent processes, namely, the polymerization in the bulk solution and at the substrate surface. The growth of the polyaniline coating at the substrate surface includes three successive processes: interfacial polymerization, adsorptive polymerization, and destruction of the polymer chain. The interfacial oxidative polymerization of diphenylamine and phenothiazine is examined. The yield and chemical structure of polymers is shown to depend on the polymerization conditions.     

自由基聚合的微型实验探索

采用微型实验进行自由基聚合是一种低成本、绿色实验,适用于教学实验,并有利于发展成设计型和综合型实验。文中,设计了自由基聚合的微型实验的方案,该方案可以充分揭示连锁聚合实施方法、工艺条件对实验所带来的差别,有利于学生对不同自由基聚合机理的掌握,起到事半功倍的效果。同时本文就微型自由基聚合实验如何体现设计型实验和综合型实验、揭示聚合工艺条件对聚合物的性能影响、自由基聚合动力学上的应用等方面的教学内容进行论述,通过实践教学环节,说明了微型实验的优势。     

浅谈自由基聚合动力学的教学与学习

自由基聚合动力学是高分子化学教学和学习中的重要内容。本文讨论了建立自由基聚合微观动力学模型的三个简化条件和三个基本假设,三个简化条件和三个基本假设是微观动力学研究聚合速率和聚合度的基础;同时也较为深入地探讨了动力学链长的物理意义、利用动力学链长概念建立起来的平均聚合度计算通用公式以及该公式的使用条件。     

聚合反应的典型影响因素分析

为了便于认识聚合反应的一般特征,本文首先比较了不同聚合方法,分析了其多步反应特征,并主要讨论了伴随反应或副反应、聚合热力学、聚合物自身性质、溶剂、聚合物分子形态对聚合反应的影响。通过揭示聚合反应的特殊性和复杂性,有助于认识聚合反应的特征及影响因素。     

微波辐射用于聚合反应的研究进展

微波辐射在高分子化学研究领域中的应用越来越广泛 ,效果也十分明显 ,与常规加热方式相比 ,微波辐射具有缩短反应时间 ,提高反应产率 ,节省能源损耗 ,制得产物性能好等优点。近年来 ,微波辐射在聚合反应中的应用也越来越多。因此本文对微波辐射在高分子聚合反应中的应用研究进行了综述。     

Recent progress on olefin polymerization catalysts

Recent progress on metallocene catalysts is reviewed. This consists for the main part of research activities in metallocene catalysts and their polymerization performances (ethylene polymerization, propylene polymerization, styrene polymerization). In addi-tion, the computational design of metallocene catalysts and the commercial status of metallocene technologies in Japan are described.     

丙烯腈在金属镁引发下的聚合动力学

研究了金属镁在硝酸溶液中引发丙烯腈的聚合反应。实验结果表明,聚合速度与金属镁的用量无关,并且当[HNO_3]>[AN]时服从下列关系式: R_p=1.91×10~5e~(-15000/RT)[Mg]~0[AN]~(2.2)[HNO_3]~(0.45) 丙烯腈-丙烯酸甲酯的共聚试验证明,聚合反应是按自由基机理进行。     

A Self-Supporting Strategy for Gas-Phase and Slurry-Phase Ethylene Polymerization using Late-Transition-Metal Catalysts

The polyolefin industry is dominated by gas-phase and slurry-phase polymerization using heterogeneous catalysts. In contrast, academic research is focused on homogeneous systems, especially for late-transition-metal catalysts. The heterogenization of homogeneous catalysts is a general strategy to provide catalyst solutions for existing industrial polyolefin synthesis. Herein, we report an alternative, potentially general strategy for using homogeneous late-transition-metal catalysts in gas-phase and slurry-phase polymerization. In this self-supporting strategy, catalysts with moderate chain-walking capabilities produced porous polymer supports during gas-phase ethylene polymerization. Chain walking, in which the metal center can move up and down the polymer chain during polymerization, ensures that the metal center can travel along the polymer chain to find suitable sites for ethylene enchainment. This strategy enables simple heterogenization of catalysts on solid supports for slurry-phase polymerization. Most importantly, various branched ultra-high-molecular-weight polyethylenes can be prepared under various polymerization conditions with proper catalyst selection.     

丙烯酰胺在聚乙二醇水溶液中的聚合动力学

用改进溴法对丙烯酰胺 (AM)在聚乙二醇 (PEG)水溶液中聚合动力学进行研究 .在单一和氧化还原引发体系中分别考察了引发剂、单体和PEG用量、不同HLB值乳化剂以及聚合温度等因素对动力学的影响 .得到AM聚合速率与过硫酸铵 (APS)浓度的 0 91次方成正比 ;单一APS和APS 三乙醇胺 (TEA)氧化还原引发体系中的AM聚合表观活化能分别为 96 1和 4 2 3kJ mol.     

Continuous Reactor Concepts with Superimposed Secondary Flow – Polymerization Process Intensification

Different unconventional continuous polymerization reactor concepts with superimposed secondary flow are presented. Exemplary polymerization reactions and the residence time distributions are discussed. In the case of the Taylor reactor polymerization process intensification is demonstrated by examples of emulsion and micro-emulsion polymerization which actually results in an increase in space time yield of up to a factor of 50.     

Model for Kinetics of Vinyl Chloride Polymerization

This paper gives a critical review of recent models for the polymerization of vinyl chloride. In solution and bulk polymerization the effect of eventual degradative chain transfer to monomer, addition of chain transfer agents, and precipitation of polymer is discussed. A model for emulsion polymerization is described which includes particle formation and kinetics of polymerization where especially desorption and reabsorption of radicals in the particles are included.     

Microemulsion polymerization of styrene in the presence of a cationic emulsifier

The principal subject discussed in the current paper is the radical polymerization of styrene in the three- and four component microemulsions stabilized by a cationic emulsifier. Polymerization in the o/w microemulsion is a new polymerization technique which allows to prepare the polymer latexes with the very high particle interface area and narrow particle size distribution. Polymers formed are very large with a very broad molecular weight distribution. In emulsion and microemulsion polymerizations, the reaction takes place in a large number of isolated loci dispersed in the continuous aqueous phase. However, in spite of the similarities between emulsion and microemulsion polymerization, there are large differences caused by the much larger amount of emulsifier in the latter process. In the emulsion polymerization there are three rate intervals. In the microemulsion polymerization only two reaction rate intervals are commonly detected: first, the polymerization rate increases rapidly with the reaction time and then decreases steadily. Essential features of microemulsion polymerization are as follows: (1) polymerization proceeds under non-stationary state conditions; (2) size and particle concentration increases throughout the course of polymerization; (3) chain-transfer to monomer/exit of transferred monomeric radical/radical re-entry events are operative; and (4) molecular weight is independent of conversion and distribution of resulting polymer is very broad. The number of microdroplets or monomer-starved micelles at higher conversion is high and they persist throughout the reaction. The high emulsifier/water ratio ensures that the emulsifier is undissociated and can penetrate into the microdroplets. The presence of a large amount of emulsifier strongly influences the reaction kinetics and the particle nucleation. The mixed mode particle nucleation is assumed to govern the polymerization process. At low emulsifier concentration the micellar nucleation is dominant while at a high emulsifier concentration the interaction-like homogeneous nucleation is operative. Furthermore, the paper is focused on the initiation and nucleation mechanisms, location of initiation locus, and growth and deactivation of latex particles. Furthermore, the relationship between kinetic and molecular weight parameters of the microemulsion polymerization process and colloidal (water/particle interface) parameters is discussed. In particular, we follow the effect of initiator and emulsifier type and concentration on the polymerization process. Besides, the effects of monomer concentration and additives are also evaluated.     

TEMPO调控下的苯乙烯光聚合

在UV光照射下, 以Irgacure 1103/TEMPO为引发剂, 实现了苯乙烯的低温光引发可控聚合, 得到了低分散性的聚苯乙烯. 与热引发聚合相比较, 光聚合的反应条件更温和, 聚合速率更快. 探讨了聚合体系中光引发剂及光强等因素的影响, 实现了光聚合产物的扩链反应.     

烯烃易位聚合研究新进展环烯烃开环易位聚合和非环二烯易位聚合

本文综述了近年来环烯烃开环易位聚合和非环二烯易位聚合研究新进展，并以活性开环易位聚合催化剂作了详细概述。     

烯烃配位聚合二十年

聚烯烃树脂是消费量最大的合成树脂种类,性能优异,用途广泛。二十多年来,烯烃配位聚合技术取得了突飞猛进的发展,在催化剂、聚合方法、聚合工艺方面都有重大突破。本文综述了二十多年来烯烃配位聚合的研究发展情况,包括Ziegler-Natta催化剂,茂金属催化剂,非茂金属催化剂,配位聚合机理,功能化聚烯烃的制备,原位共聚制备LLDPE,原位聚合制备纳米复合材料,活性配位聚合以及Spherizone工艺等方面的成就。