自由基聚合反应的新介质——离子液体的新应用

离子液体具有独特的理化性能,作为一种环境友好、"可设计性"的溶剂,近年来成为化学领域的热点和前沿。离子液体作为自由基聚合反应的溶剂,对聚合速率、聚合产物结构及性能都有一定的影响。离子液体已经被较为广泛地应用于不同介质、不同物相中的自由基聚合反应,但是并不完全。近两年来已有研究工作者将离子液体应用于微乳液和气相中的自由基聚合反应,并和其他有机溶剂及水溶液共同调控自由基聚合反应。离子液体也首次应用于有机碲调控的自由基聚合反应和氮氧稳定的自由基聚合反应。同时离子液体也可以调控自由基聚合反应后聚合物的结构和形貌,是一种很好的进行聚合物自组装的溶剂。本文主要综述了近年来离子液体对自由基聚合反应的影响,特别是对聚合产物结构及性能的影响,最后展望了离子液体在聚合反应中的应用前景。     

以离子液体为溶剂的原子转移自由基聚合

离子液体是一种有机盐,在接近室温下呈液状.离子液体是难挥发、极性高的溶剂,它能溶解很多种有机、无机和金属有机化合物.虽然有越来越多的人报道了有关离子液体在有机合成中的应用,但是在聚合过程中的应用却很少.然而在近几年,科学家证明了离子液体在聚合物的合成中的作用很大.在以离子液体为介质的自由基聚合反应中,kp/kt 会增大.尤其是在原子转移自由基聚合中,以离子液体作为溶剂有助于聚合物与残余催化剂的分离.本文主要阐述了原子转移自由基聚合反应的基本原理、特点以及离子液体在原子转移自由基聚合中的应用,并且还介绍了其他研究者的工作和原子转移自由基聚合的发展前景.     

离子液体参与原子转移自由基聚合的研究进展

主要阐述了近年来离子液体作为溶剂、单体或者配位剂在原子转移自由基聚合中的应用研究情况.从对聚合反应速率的大小的影响,聚合产物分子量多分散系数的变化,聚合物分子链功能性的设计,以及反应体系中催化体系的分离与循环使用等方面总结了离子液体的参与对原子转移自由基聚合的影响,并简要总结了导致各种变化的原因.最后展望了离子液体应用于原子转移自由基聚合技术的前景,并指出离子液体自身研究的发展是二者结合的关键问题.     

5,6-苯并-2-亚甲基-1,3-二氧环庚烷的活性自由基开环聚合反应

活性 (或称可控 )自由基聚合研究是目前高分子科学的研究热点之一[1～ 8] .活性自由基聚合制备的聚合物具有分子量随转化率提高而线性增加、分子量分布窄和聚合反应为一级反应动力学等特点 .自由基开环聚合所得产物体积收缩小 ,某些含有不饱和双键的螺环单体发生双开环聚合时甚至发生体积膨胀 ;开环聚合还可在聚合物主链上引入各种官能团 ,如酯基、碳酸酯基、酮基等 [9～ 12 ] .因此 ,用活性聚合的方法对自由基开环聚合的分子量和分子量分布进行控制 ,可以制备出具有各种不同结构和性能的新聚合物 . Wei等 [13] 报道了利用稳定自由基法实现…     

离子液体中的聚合反应研究进展

室温离子液体是一种新兴的可替代挥发性有机化合物（VOCs）的绿色溶剂和高效的反应介质，为减少或消除化学反应和过程工程中的环境问题提供了重要的途径。以离子液体为反应介质进行聚合反应，可消除或减小VOCs的危害，也可实现催化剂的有效回收利用和聚合物的纯化，更好地控制聚合反应及聚合产物的结构与性质、乃至直接用作高效的聚合催化剂。本文综述近年来离子液体中聚合反应的研究现状及最新进展，分析现存的问题，并展望今后的发展方向。     

红外光谱法研究苯乙烯原子转移自由基聚合反应动力学

利用红外光谱法测定反应转化率研究原子转移自由基聚合反应动力学。在环己酮溶液中,以卤代烃为引发剂,过渡金属卤化物与配位剂２,２‘－联吡啶为催化体系,进行了苯乙烯聚合。分别就反应温度,反应物浓度和引发体系对苯乙烯聚合速率的影响进行了动力学测定,证实了原子转移自由基聚合具有活性聚合的特征,同时计算并讨论了苯乙烯原子转移自由基聚合反应的动力学数据。     

波聚合体系、引发、过程及应用

波聚合是一种通过局部反应区域向未反应区域连续移动将单体转化为聚合物的反应模式,具有简便快速、节能降耗和产物性能优异等优势,是化学合成、功能材料与结构材料制备的新方法。本文对波聚合反应体系、引发、过程、应用及存在问题等方面进行综述。重点评述了新型波聚合体系如二元或多元体系、离子液体体系、深共晶溶剂体系等;新型引发剂如光引发剂和离子液体引发剂等特殊引发剂;波聚合反应体系中的助剂如填料、交联剂、链转移剂、活化剂、增稠剂、表面活性剂和催化剂等对聚合过程和产物结构性能的影响;新发展的引发方式如紫外线、水、等离子体和耦合引发等;以及特殊波聚合过程。最后,展望了波聚合存在问题和商业化应用的研究方向。     

丙烯腈在1-丁基-3-甲基咪唑氯化物中的聚合及其表征

以离子液体1-丁基-3-甲基咪唑氯化物([bmim]Cl)为溶剂,研究了丙烯腈(AN)的自由基均聚和共聚反应,通过红外光谱(FT-IR)和核磁共振(NMR)分析了聚合产物的化学结构,研究了第二单体丙烯酸甲酯(MA)的含量对聚合反应速率及转化率的影响.结果表明:以离子液体为溶剂所得聚丙烯腈(PAN)的化学结构与在常规溶剂中的一致,聚合产物的组成比与投料比接近,分子量随着AN含量的增加而增大,反应转化率随着AN含量的增加先增大后减小,所得PAN的分子量分布窄(<1.7)、分子量高.差示扫描量热分析(DSC)结果表明:MA含量低于2%时有利于环化反应的控制.     

混杂聚合

混杂聚合是指同一体系内有两种或两种以上不同类型的聚合反应同时进行的过程,如自由基聚合与阳离子聚合,自由基聚合与缩聚等。混杂聚合能够在原位形成高分子合金,并有可能得到互穿网络结构（ＩＰＮ）,从而使聚合产物具备较好的综合性能。     

可逆加成—断裂链转移自由基聚合在制备水溶性聚合物中的应用

水溶性聚合物在工业、农业、医药等领域都有着广泛用途,但随着近年对水溶性聚合物精细化的要求,寻找新的结构可控的聚合方法已成为迫切需求.由于可逆加成-断裂链转移(RAFT)自由基聚合具有适用单体范围广、反应条件温和、不受聚合方法的限制等优点,以及可控制聚合物的嵌段、接枝、梳型、星型、无规及梯度等结构,成为合成结构可控的水溶性聚合物的最有效手段之一.本文主要讨论了单体、引发剂、链转移剂、溶剂等组成对RAFT聚合反应的影响,并介绍了利用RAFT方法制备非离子、阴离子、阳离子及两性离子水溶性聚合物的实例.     

Ionic liquids in the synthesis and modification of polymers

Ionic liquids are organic salts that are liquid at ambient temperatures, preferably at room temperature. They are nonvolatile, thermally and chemically stable, highly polar liquids that dissolve many organic, inorganic, and metallo‐organic compounds. Many combinations of organic cations with different counterions are already known, and the properties of ionic liquids may be adjusted by the proper selection of the cation and counterion. In the last decade, there has been increasing interest in using ionic liquids as solvents for chemical reactions. The interest is stimulated not only by their nonvolatility (green solvents) but also by their special properties, which often affect the course of a reaction. In recent years, ionic liquids have also attracted the attention of polymer chemists. Although the research on using ionic liquids in polymer systems is still in its infancy, several interesting possibilities have already emerged. Ionic liquids are used as solvents for polymerization processes, and in several systems they indeed show some advantages. In radical polymerization, the k_p/k_t ratio (where k_p is the rate constant of propagation and k_t is the rate constant of termination) is higher than in organic media, and thus better control of the process can be achieved. Ionic liquids, as electrolytes, have also attracted the attention of researchers in the fields of electrochemical polymerization and the synthesis of conducting polymers. Finally, the blending of ionic liquids with polymers may lead to the development of new materials (ionic liquids may act as plasticizers, electrolytes dispersed in polymer matrices, or even porogens). In this article, the new developments in these fields are briefly discussed. © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 43: 4675–4683, 2005     

Water-soluble ionic liquids as novel stabilizers in suspension polymerization reactions: engineering polymer beads

Aqueous solutions of ionic liquids have been used as novel and environmentally friendly reaction media to synthesize and "control" the size of different cross-linked polymer beads by suspension polymerization reactions. It was found that the investigated ionic liquids can act as novel stabilizing agents of the suspensions as a result of their surface-active properties. The results have demonstrated that the average size of polymer beads can be varied from the macro- to the nanoscale and their surface area can also be "adjusted" by this synthetic approach. Furthermore, the use of a combination of ionic liquids and water for the synthesis of polymers, the simple isolation of the products formed in this polymerization procedure, as well as the recycling of the continuous medium for further reactions open up possibilities for the development of "new and green" polymerization processes.     

Cationic polymerization of styrene involving ionization of the C?Cl bond in ionic liquid/SO2 mixture

There has been a recent upsurge in interest in use of ionic liquids as reaction media for various chemical processes. Until recently, ionic liquids were considered as highly polar solvents. Our earlier investigation indicated that cationic polymerization of styrene initiated by aryl (alkyl) chlorides in ionic liquids may proceed even in the absence of coinitiator (Lewis acid). Polymerization, however, did not conform to controlled polymerization scheme. More recently, it has been claimed that ionic liquids are not as polar as it was previously assumed. Independently, high solubility of sulfur dioxide in ionic liquids was noticed. As sulfur dioxide displays a high ionizing power toward organic halides, we applied ionic liquid/sulfur dioxide mixture as a solvent in cationic polymerization of styrene initiated by aryl (alkyl) chlorides. Results show that in this reaction medium ionization of the C? Cl bond is facilitated, and the contribution of chain transfer reaction can be reduced as compared with polymerization in ionic liquid alone. Ionization of the C? Cl bond, however, is still not sufficiently fast to ensure conditions of controlled polymerization. © 2009 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 47: 5251–5257, 2009     

微波促进离子液体相反应在有机合成中的应用

微波促进离子液体相有机合成技术作为一种新型的绿色化学合成法,引起了人们极大的兴趣。在离子液体中,微波辅助下反应快速、收率高、选择性好、后处理简单,离子液体经简单再生后可多次套用。本文综述了以离子液体为反应介质或催化剂的微波辅助技术在多种类型有机反应中的研究成果,主要包括了环合反应、亲核取代反应、金属复分解反应、酰化反应、重排反应、聚合反应、偶联反应、氧化还原反应和选择性脱溴反应等。     

Sonochemical polymerization of miniemulsions in organic liquids/water mixtures

The sonochemical oil-in-water miniemulsion polymerization of n-butyl methacrylate (BMA) has been studied in mixtures with a range of aliphatic and aromatic hydrocarbon liquids under ambient conditions. Measurements of monomer conversion percentage and molecular weights of the BMA polymers were performed to investigate the effect of the various organic liquids on the kinetics of the polymerization process and on the properties of the resultant polymers. Both the rates of polymerization and the molecular weights of the polymers formed were found to be dependent on the amount and type of the organic liquid present in the emulsion. The experimental results revealed that when the organic liquids were aliphatic, there were no significant changes in the rates of BMA polymerization whereas when the organic liquids were aromatic, the rates of polymerization were greatly reduced. Molecular weight data of the BMA polymers showed that in the presence of an organic liquid, the size of the polymer significantly decreased. The results have been interpreted in terms of the formation of a radical complex between the propagating radical and the organic liquid in the oil mixture, as well as chain transfer reactions that affect the kinetics of the polymerization process.     

Review: Current studies on some physical properties of ionic liquids

As a novel substituting solvent for organic solvents, low-temperature ionic liquids have attracted much attention as good media in organic synthesis and other chemical processes. Better understanding of physical properties of ionic liquids are very helpful in exploring reaction mechanisms and controlling reaction outputs. This review summarises current studies on several physical properties (melting point, vapor pressure and stability, polarity, miscibility, density, viscosity) that are important for organic reactions.     

Systematic Investigation of the Photopolymerization of Imidazolium-Based Ionic Liquid Styrene and Vinyl Monomers

The use of ionic liquids (ILs) as media in radical polymerizations has demonstrated the ability of these unique solvents to improve both reaction kinetics and polymer product properties. However, the bulk of these studies have examined the polymerization behavior of common organic monomers (e.g., methyl methacrylate, styrene) dissolved in conventional ILs. There is increasing interest in polymerized ILs (poly(ILs)), which are ionomers produced from the direct polymerization of styrene-, vinyl-, and acrylate-functionalized ILs. Here, the photopolymerization kinetics of IL monomers are investigated for systems in which styrene or vinyl functionalities are pendant from the imidazolium cation. Styrene-functionalized IL monomers typically polymerized rapidly (full conversion ≤1 min) in both neat compositions or when diluted with a nonpolymerizable IL, [C₂mim][Tf₂N]. However, monomer conversion in vinyl-functionalized IL monomers is much more dependent on the nature of the nonpolymerizable group. ATR-FTIR analysis and molecular simulations of these monomers and monomer mixtures identified the presence of multiple intermolecular interactions (e.g., π–π stacking, IL aggregation) that contribute to the polymerization behaviors of these systems. © 2018 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2018 , 56, 2364–2375     

Free Radical Polymerization of Acrylonitrile in Green Ionic Liquids

Free radical polymerization of acrylonitrile (AN) in ionic liquid, 1-butyl-3-methylimidazolium tetrafluoroborate ([bmim][BF₄]), 2,2;m1-azobisisobutyronitrile (AIBN) as initiator was investigated. Early investigations on polymerizations using ionic liquids indicate that they serve as especially good solvents to achieve high molecular weight polymers. Free radical polymerizations result in higher molecular weight polymers, for ionic liquids have low chain transfer constants and act to stabilize the active radical during the process of polymerization. The thermal stability of polymers synthesized in ionic liquids have be improved obviously than that in traditional solvents.