活性聚合,表现活性聚合和准活性聚合

活性聚合是连锁聚合反应体系中链转移和终止反应速率为零时的特殊反应类型，表现活性聚合和准活性聚合则是链转移或终止反应未被完全消除而人有活性聚合物特征两类聚合物反应，是非活性聚合活性聚合过渡和逼近时的两种聚合反应类型，本文对活性聚合，表现活性聚合和准活性聚合的基本概念及它们之间的区别作了简单的介绍。     

ACPMA/BPO引发甲基丙烯酸甲酯聚合及其动力学

以4,4′-偶氮二[4-氰基戊酰(对-二甲氨基)苯胺](ACPMA)/过氧化二苯甲酰(BPO)为氧化还原引发体系,研究了甲基丙烯酸甲酯(MMA)在N,N-二甲基甲酰胺(DMF)中的聚合及其动力学行为.考察了聚合反应温度、单体浓度、ACPMA浓度和BPO浓度对聚合反应速率和聚合物分子量的影响,测定了反应级数和聚合反应的活化能.结果表明,在一定范围内,聚合反应速率随单体浓度增大、ACPMA浓度增大、BPO浓度增大和反应温度的升高而增大;聚合物分子量随单体浓度的增大而增大,随ACPMA浓度的增大、BPO浓度增大和反应温度的升高而降低.该体系具有氧化还原引发体系的特征,其引发MMA的聚合速率方程为Rp=K[ACPMA]0.57     

ATRP法合成结构对称的双羧基聚苯乙烯及其超分子的形成

从二甲苯出发,经过溴甲基化反应、氧化反应、酯化反应和溴代反应,合成了一种四官能团的引发剂,4,6-二(溴甲基)-1,3-苯二甲酸二甲酯.用该引发剂引发苯乙烯进行原子转移自由基聚合,实验结果表明聚合反应具有活性自由基聚合的特征.通过苯乙烯的本体聚合反应获得了分子量可控、双酯基位于聚合物链中间的聚苯乙烯.经过水解反应,使聚合物中的双酯基被水解成双羧基,从而得到了结构对称的两亲性聚合物,双羧基聚苯乙烯.利用该聚合物具有分子识别的特性,与十二烷胺形成了离子键超分子化合物.此工作为超分子星形聚合物的设计合成提供了简便快捷的方法.     

AIBN/SmCl3/乳酸体系催化甲基丙烯酸甲酯的反向原子转移自由基聚合

利用稀土金属化合物三氯化钐(SmCl3)和二氯化钐(SmCl2)之间的单电子转移反应,以AIBN/SmCl3/乳酸作为反向原子转移自由基聚合(ReverseATRP)的催化体系,成功地实现了甲基丙烯酸甲酯(MMA)的反向ATRP,并考察了温度、溶剂和组分比对聚合反应的影响.MMA在该体系中的聚合反应是一级反应,所得PMMA的分子量与单体转化率成正比,聚合物的分子量分布较窄(Mw/Mn<1.5),具有活性聚合的特征.     

离子液体在自由基聚合反应中的应用研究进展

室温离子液体是完全由离子构成的液体,具有几乎没有蒸汽压、溶解度大、溶解范围广、易于回收利用、稳定性好等特点,广泛应用于电化学、有机反应、分离萃取、复合材料等各个领域。近年来已成为各种聚合反应研究的重要课题,且主要集中于自由基聚合反应。作为聚合反应的溶剂,离子液体对聚合反应速率、分子量、聚合物的结构性能都有一定影响。本文根据近几年的文献,归纳分析了离子液体中的常规自由基聚合和活性自由基聚合的反应动力学、反应机理、聚合产物的结构和性能以及离子液体的回收利用等问题。     

丙烯酸酯/液晶体系的光聚合反应动力学对PDLC电光性质的影响

采用光-示差扫描量热法(P-DSC)和光-流变学(P-Rheology)技术,测定了丙烯酸酯/液晶体系的光聚合反应动力学和凝胶化时间.基于自催化模型和凝胶时间-温度关系,计算了体系的光聚合反应速率常数和活化能,探讨了单体结构与组成、反应温度对体系光聚合动力学的影响,并研究了聚合物分散液晶(PDLC)的电光响应行为与相分离结构对光聚合动力学的依赖性.结果表明,升高反应温度、增加体系的单体反应活性和平均官能度,均提高了体系的光聚合速率常数,缩短了光聚合凝胶时间.随着单体反应活性和平均官能度的提高,体系的光聚合反应活化能明显降低,且凝胶化前的光聚合反应活化能低于光聚合全过程的平均反应活化能.当液晶含量为50%时,形成的PDLC呈亚微米尺度的双连续相结构.随着光聚合反应温度的升高,光聚合速率加快,导致凝胶时间缩短、相分离程度降低,使PDLC中液晶相尺寸变小、聚合物网络致密化,PDLC的弛豫时间延长、饱和电压降低,而开启时间和阈值电压变化不大.     

碳纳米管的聚合物功能化与结构控制:聚合物接枝碳纳米管

碳纳米管高分子化是发展高性能的聚合物基纳米功能材料的重要研究方向,本文从"grafting-to"和"grafting-from"两种方式对聚合物接枝碳纳米管的最新进展进行了系统综述。"Grafting-to"方法主要包括羧基衍生反应(酰化、酯化)、加成反应(大分子自由基加成、叠氮环加成)和硫醇偶联反应。"Grafting-from"方法包括普通自由基聚合、可控/活性自由基聚合、离子聚合、开环聚合和逐步聚合反应,其中碳纳米管表面引发活性自由基聚合进一步分为原子转移自由基聚合、氮氧稳定自由基聚合和可逆加成-断链转移聚合。此外,本文还简述了碳纳米管自身的聚合反应,并探讨了目前聚合物修饰碳纳米管所面临的问题和今后的发展方向。     

Fe-Zn双金属氰化物催化环氧丙烷开环聚合的研究

用Fe Zn双金属氰化物 (DMC)催化剂合成了数均分子量 30 0 0～ 12 0 0 0的聚氧化丙烯二元醇 .着重考察了聚合反应的温度、加料方式等对聚合物分子量及分布的影响 ,并初步探讨了Fe Zn双金属氰化物催化环氧丙烷开环聚合的反应特征 .实验发现 ,采用Fe ZnDMC催化剂 ,聚合物分子量可控 ;在较高温度下聚合所得的聚合物分子量分布呈双峰形 ,显示反应体系中至少存在两类活性中心 ,这可能与催化剂中存在两种价态的络合物有关 ,当降低聚合温度时 ,聚合物分子量分布呈单峰形 ,可能是一类活性中心没有引发 ;实验中还发现单体分批加料时聚合物分子量分布较窄 ,而一步加料法所得聚合物分子量分布则很宽     

由平面合成聚合物刷--表面引发原子转移自由基聚合研究进展

原子转移自由基聚合反应(ATRP)是实现活性聚合,获得可控聚合物的一种有效途径。通过表面引发原子转移自由基聚合,在材料表面合成聚合物刷,是改变材料表面特征的有效方法。本文综述了表面引发原子转移自由基聚合合成聚合物刷及其最新进展。     

FeBr3/Me6TREN催化MMA反向原子转移自由基聚合研究

对FeBr3/Me6TREN催化的反向原子转移自由基聚合进行了研究.在不同的催化剂、引发剂的配比、聚合温度和配体用量等条件下,该催化体系催化的MMA聚合反应动力学为一级反应,聚合物分子量可控,分子量分布很窄,说明该体系催化的聚合反应为活性可控聚合.通过实验计算了反应的活化能,并利用UV光谱对催化剂进行了研究.     

有关“自动加速效应”问题的总结与讨论

自动加速效应是自由基聚合宏观动力学的重要特征,对聚合过程和聚合产物有着重要的影响;有关自动加速效应的内容也是自由基聚合动力学教学的重难点之一。为帮助学生较好地理解和掌握自动加速效应相关内容,本文结合有关高分子化学教材,对自动加速效应的实验现象、与体型缩聚凝胶化过程的区别、产生原因、结果和影响因素等问题进行了总结和讨论。     

The polymerization of furfuryl acetate in acetonitrile

The complex resins derived from furfuryl-alcohol polymerization are a result of at least four competing reactions. By converting the alcohol to its acetate ester, however, three of these reactions can be eliminated. The simpler polymer derived from furfuryl acetate has been characterized spectroscopically, and an interesting chromophoric side reaction of the polymerization has been identified. The remarkable ability of the polymer to crosslink at room temperature upon precipitation from solution is also of interest.     

Standing on the shoulders of Hermann Staudinger: Post‐polymerization modification from past to present

With a span as long as the history of polymer science itself, post‐polymerization modification represents a versatile platform for the preparation of diversely functionalized polymers from a single precursor. Starting with the initial efforts by Staudinger in the 1920s, many of the early developments in modern polymer science can be attributed to the utilization of post‐polymerization modification reactions. The scope of post‐polymerization modification has greatly expanded since the 1990s due to the development of functional group tolerant controlled/living polymerization techniques combined with the (re)discovery of highly efficient coupling chemistries that allow quantitative, chemoselective, and orthogonal functionalization of reactive polymer precursors. After some basic mechanistic considerations, this Highlight will provide an overview of the development and evolution of eight main classes of post‐polymerization modification reactions. © 2012 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2013     

自蔓延波聚合研究进展

波聚合是指靠自身反应放热产生的热波维持反应进行而将单体转化为聚合物的聚合方法。由于波聚合不需要外界持续供热、无溶剂排放和反应设备简单,是一种节能无污染的低成本材料制备工艺,极具应用前景。本文综述了从发现波聚合至今已取得的研究成果,包括波聚合机理、聚合波产生并自蔓延的条件、波结构、传播速度、传播模式以及产物特征,并对波聚合工艺用于高分子材料的制备进行了评述。     

Recent Advances in Automatic Continuous Online Monitoring of Polymerization Reactions (ACOMP)

ACOMP allows comprehensive, model-independent, near realtime monitoring of many different types of polymerization reactions. It provides conversion kinetics, and the evolution of average molar mass, intrinsic viscosity and average composition distributions (for copolymers). Here, recent advances in ACOMP will be summarized, dealing with continuous reactors, copolymerization, ‘living’ type reactions (NMP, RAFT, ATRP, ROMP), polyelectrolytes, heterogeneous phase reactions, including free radical reactions in emulsions, and predictive control. In the case of emulsion polymerization, a new approach will be presented in which the evolution of the characteristics of both the soluble phase – monomer conversion, polymer molar mass and intrinsic viscosity- and the dispersed phase – particle size – are simultaneously monitored. NSF CBET 0623531, BoR ITRS 019B, NASA NCC3-946, TIMES, PolyRMC (Tulane Center for Polymer Reaction Monitoring and Characterization).     

Orthogonal synthesis and modification of polymer materials

In this review, we detail the progress throughout the years toward developing truly orthogonal polymerization mechanisms and modification procedures en route to complex macromolecular structures built from synthetic polymer materials. The orthogonal modifications of polymer side-chains and end-groups via sequential click reactions is described providing post-polymerization routes to functional materials and unique polymer topologies. Further, historical and modern orthogonal polymerization methodologies are thoroughly reviewed showing the evolution of the field through the decades long study of selective polymerization mechanisms that provide unique copolymer structures that are typically difficult to achieve. These include the combinations of reversible deactivation radical polymerization mechanisms with a variety of polymerization mechanisms including ring opening polymerizations, ring opening metathesis polymerizations, and cationic polymerizations, to name a few.     

The synthesis,interfacial, and colloidal properties of waterborne cationic methacrylic co-polymers

Two cationic polymers with similar composition were prepared by two different polymerization methods. By monitoring the evolution of the molar mass and chemical composition during the reactions together with charge density measurements and calculations, it was concluded that the cationic polymer synthesized by emulsion polymerization had a less uniform compositional distribution than the cationic polymer prepared by solution polymerization. Contributing to the heterogeneity was the hydrolysis of one monomer (dimethylamino ethylmethacrylate (DMAEMA)) during the synthesis. As a result, the polymer prepared by emulsion polymerization had a more blocky structure and was more surface active as supported by static and dynamic surface tensions data. Fluorescence experiments showed that both polymers formed aggregates at very low concentrations of approximately 0.01 wt%. The aggregates of the polymer prepared by emulsion polymerization were compact, whereas the solution polymerization-based polymer aggregates exhibited a rather expanded geometry.     

STUDIES ON THE DYNAMIC MECHANICAL BEHAVIOR OF POLYMERIZATION OF BIS(4-(4-ETHYNYLPHENOXY)PHENYL)SULFONE AND ITS POLYMERS

The dynamic mechanical behavior and structural characteristics of polymerization bis(4-(4-ethynylphenoxy)phenyl)sulfine(ESF) and its polymers were investigated by means of tcrsional braid analysis(TBA) and infrared spectroscopy.Results show that the multiple transitions including the melting,low-temperature and high-temperature reactions of ESF oligomers,glass transition and decomposition reaction of resulted polymer can be characterized in the TBA spectra.The glass transition tempe: atures and structural characteristics of ESF polymers depend upon the conditions of polymerization.     

Versatile Reactions of Organoboron Polymers Prepared by Hydroboration Polymerization

Hydroboration polymerization of dienes and thexylborane produces organoboron polymers, which can be regarded as a polymer homolog of trialkylboranes. In other words, the organoboron polymers obtained can be expected to be a novel type of reactive polymer. The present paper describes versatile reactions of organoboron polymers prepared by hydroboration polymerization. For example, reactions with carbon monoxide or with KCN were followed by oxidative treatment to produce the corresponding poly(alcohol)s or poly(ketone)s, respectively. The organoboron polymers were also reacted with bromopyridyl anion or with furyl anion to form cyano- or hydroxyl-containing polymers via ring-opening of pyridine or furan, respectively. Reductive treatment of the organoboron polymer gave the corresponding polymer after reductive cleavage of carbon—boron bonds.     

Modeling and Experimentation of RAFT Solution Copolymerization of Styrene and Butyl Acrylate,Effect of Chain Transfer Reactions on Polymer Molecular Weight Distribution

Chain transfer reactions widely exist in the free radical polymerization and controlled radical polymerization, which can significantly influence polymer molecular weight and molecular weight distribution. In this work, the chain transfer reactions in modeling the reversible addition–fragmentation transfer (RAFT) solution copolymerization are included and the effects of chain transfer rate constant, monomer concentration, and comonomer ratio on the polymerization kinetics and polymer molecular weight development are investigated. The model is verified with the experimental RAFT solution copolymerization of styrene and butyl acrylate, with good agreements achieved. This work has demonstrated that the chain transfer reactions to monomer and solvent can have significant impacts on the number‐average molecular weight (M_n) and dispersity (Ð).