Side-Chain Metallocene-Containing Polymers by Living and Controlled Polymerizations

This review summarizes recent work on side-chain metallocene-containing polymers prepared by controlled and living polymerizations, which include living anionic polymerization (LAP), ring-opening metathesis polymerization (ROMP) and controlled radical polymerization (CRP) such as atom transfer radical polymerization (ATRP), reversible addition fragmentation chain transfer polymerization (RAFT), and nitroxide-mediated polymerization (NMP). The majority of efforts in the field are focused on side-chain ferrocene-containing polymers, while cobaltocenium-containing polymers have recently started to draw attention. Future direction on the development of other metallocene-containing polymers is discussed.     

Metallopolymers with transition metals in the side-chain by living and controlled polymerization techniques

Work on side-chain transition metal-containing polymers prepared by controlled and living polymerizations is summarized, including living anionic polymerization (LAP), ring-opening metathesis polymerization (ROMP) and controlled radical polymerization (CRP) such as atom transfer radical polymerization (ATRP), reversible addition-fragmentation chain transfer polymerization (RAFT), and nitroxide-mediated polymerization (NMP). These polymers include metallocene-containing polymers, ferrocenylsilane polymers with additional metal at the side chain, metal carbonyl complex polymers, and ligated metal complex polymers.     

RAFT (Reversible addition–fragmentation chain transfer) crosslinking (co)polymerization of multi‐olefinic monomers to form polymer networks

The use of reversible addition–fragmentation chain transfer (RAFT) crosslinking (co)polymerization of multi‐olefinic monomers to produce three‐dimensional polymer networks is reviewed. We give specific attention to differences between RAFT and conventional processes, differences between RAFT and other forms of reversible deactivation radical polymerization (such as atom transfer radical and nitroxide‐mediated polymerizations) and the dependence of the polymerization process and network properties on RAFT agent structure. This knowledge is important in network optimization for applications as dynamic covalent polymers (in self‐healing polymers), as porous polymer monoliths or gels (used as chromatographic media, flow reactors, controlled release media, drug delivery vehicles and in molecular imprinting) and as coatings. © 2014 Society of Chemical Industry     

The application of ionizing radiation in reversible addition-fragmentation chain transfer (RAFT) polymerization: Renaissance of a key synthetic and kinetic tool

Ionizing radiation, such as γ, ultraviolet, microwave and X-ray radiation, has long been used in polymer chemistry as a means of initiating polymerization, crosslinking gels and decomposing particular polymer components. More recently, ionizing radiation has found application in tandem with living radical polymerization to form novel polymeric materials with defined molecular weight and narrow molecular weight distribution. In particular, γ-rays and ultraviolet light both have shown promise as sources of initiation in reversible addition-fragmentation chain transfer (RAFT) polymerization. The ability to apply these sources of initiation at low temperatures is useful in applications where elevated temperature is likely to be detrimental to the system, for instance, in preparing protein-polymer conjugates. Similarly, the use of these initiating sources at low temperature is particularly suitable for some monomers, such as allyl compounds, which have not been synthesized using any other living radical approach. The current review examines the development of ionizing radiation as a tool in RAFT polymerization, with particular reference to the elucidation of the polymerization mechanism, the synthesis of high functionality polymers and probing the kinetic parameters of the RAFT process.     

Radical addition-fragmentation chemistry in polymer synthesis

This review traces the development of addition-fragmentation chain transfer agents and related ring-opening monomers highlighting recent innovation in these areas. The major part of this review deals with reagents that give reversible addition-fragmentation chain transfer (RAFT). These reagents include dithioesters, trithiocarbonates, dithiocarbamates and xanthates. The RAFT process is a versatile method for conferring living characteristics on radical polymerizations providing unprecedented control over molecular weight, molecular weight distribution, composition and architecture. It is suitable for most monomers polymerizable by radical polymerization and is robust under a wide range of reaction conditions. It provides a route to functional polymers, cyclopolymers, gradient copolymers, block polymers and star polymers.     

Synthesis of 9H-fluoren-9-yl benzodithioates and their application as reversible addition–fragmentation chain transfer agents in living radical polymerization of styrene

The reversible addition–fragmentation chain transfer (RAFT) polymerization is one of living radical polymerizations. In this study, four different 9H-fluoren-9-yl benzodithiolates (FBDTs) were synthesized, and used along with azobis(isobutyronitrile) (AIBN), a radical initiator, in polymerization of styrene (ST) at the molar ratio of 3:1. This new transfer agent exhibited the typical characteristic living free radical polymerization behaviors such as good control of molecule weight and narrow molecule weight distribution. It was concluded that the FBDTs can be used as the RAFT agents in free radical polymerization of vinyl monomers.     

活性自由基乳液聚合的研究进展

活性自由基乳液聚合是一个非常新的研究领域。介绍了目前活性自由基乳液聚合领域的3种常用的方法及应用这些方法进行乳液聚合的研究进展,包括:原子转移自由基聚合(ATRP),氮氧调节自由基聚合(NMP)和可逆加成-断裂链转移自由基聚合(RAFT)。     

基于RAFT聚合策略合成功能化聚烯烃嵌段聚合物的研究进展

首先介绍了可逆加成-断裂链转移聚合（RAFT）的聚合机理及其常用的RAFT试剂,并与其它两种活性可控自由基聚合[氮氧化合物媒介的自由基聚合（NMP）和原子转移自由基聚合（ATRP）]进行了简单的优缺点对比。其次,介绍了近些年在基于RAFT聚合制备功能化聚烯烃嵌段聚合物研究中取得的进展,重点综述了制备功能化聚烯烃嵌段聚合物时所采用的6种方法,包括①烯烃配位聚合与RAFT聚合相结合;②阴离子聚合与RAFT聚合相结合;③阳离子聚合与RAFT聚合相结合;④Click反应与RAFT聚合相结合;⑤开环聚合与RAFT聚合相结合;⑥叶立德活性聚合与RAFT聚合相结合。最后,对基于RAFT聚合策略设计合成功能化聚烯烃嵌段聚合物的研究前景与实际应用进行了展望。     

Photomediated controlled radical polymerization

Photomediated controlled radical polymerization is a versatile method to prepare, under mild conditions, various well-defined polymers with complex architecture, such as block and graft copolymers, sequence-controlled polymers, or hybrid materials via surface-initiated polymerization. It also provides opportunity to manipulate the reaction through spatiotemporal control. This review presents a comprehensive account of the fundamentals and applications of various photomediated CRP techniques, including atom transfer radical polymerization (ATRP), reversible addition-fragmentation chain transfer (RAFT), nitroxide mediated polymerization (NMP) and other procedures. In addition, mechanistic aspects of other photomediated methods are discussed.     

Efficient synthesis of two or multi component block copolymers through living radical polymerization with polymeric photoiniferters

Summary To synthesize efficiently block copolymers, the radical polymerization of vinyl monomers with the polymers obtained by tetraethyl thiuram disulfide(TD) as polymeric photoiniferters has been investigated. These photopolymerizations were found to proceed via a living radical mechanism, i.e. both the whole polymer yields and the average molecular weight of the block copolymers increased with increasing of the polymerization time. By applying these living radical polymerizations, various block copolymers consisting of two, three and four component blocks were obtained in good yields, suggesting that these techniques are effective and useful for synthesizing multi component block copolymers through radical polymerizations of polar vinyl monomers.     

Microwave-Assisted RAFT Polymerization

Advances in controlled radical polymerization (CRP) have facilitated access to well-defined polymers with controlled molecular weight, topology, and functionality. However, despite the benefits afforded by many CRP techniques, control over these key polymer attributes often comes at the expense of polymerization rate. One method proposed for accelerating chemical synthesis is microwave heating. This review highlights recent examples of microwave heating being applied during reversible addition-fragmentation chain transfer (RAFT) polymerization. In addition to successfully leading to homopolymers from a variety of monomers, block copolymers have also been prepared by microwave-assisted RAFT, which suggests that the high polymerization rates observed do not necessarily lead to significant end group loss from termination. Despite significant debate regarding the origin of rate enhancement observed during microwave-assisted reactions, the reports included herein provide insight into mechanisms by which well-defined functional polymers can be prepared in an accelerated fashion.     

End‐functional polymers,thiocarbonylthio group removal/transformation and reversible addition–fragmentation–chain transfer (RAFT) polymerization

This review focuses on processes for thiocarbonylthio group removal/transformation of polymers synthesized by radical polymerization with reversible addition‐fragmentation‐chain transfer (RAFT). A variety of processes have now been reported in this context. These include reactions with nucleophiles, radical‐induced reactions, thermolysis, electrocyclic reactions and ‘click’ processes. We also consider the use of RAFT‐synthesized polymers in the construction of block or graft copolymers, functional nanoparticles and biopolymer conjugates where transformation of the thiocarbonylthio group is an integral part of the process. This includes the use of RAFT‐synthesized polymers in other forms of radical polymerization such as atom transfer radical polymerization or nitroxide‐mediated polymerization, and the ‘switching’ of thiocarbonylthio groups to enable control over polymerization of a wider range of monomers in the RAFT process. With each process we provide information on the scope and, where known, indicate the mechanism, advantages and limitations. Copyright © 2011 Society of Chemical Industry     

甲基丙烯酸酯/二甲基丙烯酸酯自由基共聚合体系中的自加速和凝胶行为

对甲基丙烯酸聚乙二醇单醚酯/二甲基丙烯酸聚乙二醇酯共聚体系分别实施常规自由基聚合（FRP）,原子转移自由基聚合（ATRP）和可逆加成-断裂链转移（RAFT）自由基聚合,通过观察聚合速率、双键转化率、凝胶点以及交联网络的发展,比较FRP、ATRP和RAFT共聚合体系的反应动力学和交联行为。3个聚合体系均出现了自加速现象,ATRP体系的自加速由扩散控制的自由基脱活造成,RAFT体系的自加速来自于扩散控制的自由基加成。在ATRP和RAFT交联体系中,初级链的缓慢增长和充分松弛减少了分子内环化,抑制了微凝胶形成,因此其凝胶点远低于FRP体系。ATRP和RAFT交联网络通过凝胶自由基与单体加成以及支化链的结合而不断发展,导致凝胶含量和交联网络密度随转化率不断增大。     

结构可控含氟共聚物的合成及其应用研究新进展

近年来,含氟聚合物以其优异的耐热性、耐氧化性、耐候性、耐腐蚀性以及低介电常数、低表面能等特点,在疏水材料、抗污材料、表面活性剂、造影剂等领域具有广泛的应用前景,受到研究者的密切关注,各种拓扑结构的含氟共聚物被设计合成出来并在相关领域得到应用。本文首先简要介绍了含氟聚合物的性质和研究现状,然后详细叙述了可逆加成-断裂链转移聚合（RAFT）、原子转移自由基聚合（ATRP）、碘转移自由基聚合（ITP）、单电子转移活性聚合（SET-LRP）、氮氧稳定自由基聚合（NMP）以及活性阴离子聚合（LAP）等聚合方法在结构可控含氟共聚物合成中的研究新进展,并对其聚合机理、优缺点以及所得共聚物的性质和应用进行了总结,最后对结构可控含氟共聚物的设计、合成及实际应用前景进行了展望,提出发展绿色环保功能性含氟聚合物将是未来的主要研究热点。     

A 20th anniversary perspective on the life of RAFT (RAFT coming of age)

RAFT (reversible addition–fragmentation chain transfer) polymerization, making use of thiocarbonylthio transfer agents, was announced to the world just over 21 years ago. RAFT arose out of a desire to achieve perfection in polymers (or at least to define and limit the imperfections) and to invent living radical polymerization. However, living radical polymerization cannot be and never was. This perspective looks at RAFT after 21 years of development. Is RAFT a mature technology? We briefly summarize areas of current interest focusing on what is happening at CSIRO and point to where RAFT is going in areas such as RAFT free from exogenous initiators (photoRAFT, PET‐RAFT, eRAFT), new RAFT agents, RAFT for sequence‐defined polymers and RAFT single unit monomer insertion, RAFT emulsion polymerization and RAFT polymerization‐induced self‐assembly (PISA), RAFT‐crosslinking polymerization and the industrial applications of RAFT. © 2019 Society of Chemical Industry     

Poly(vinyl acetate) and Poly(vinyl propionate) Star Polymers via Reversible Addition Fragmentation Chain Transfer (RAFT) Polymerization

Summary Poly(vinyl acetate) and poly(vinyl propionate) star polymers with four arms were produced via reversible addition fragmentation chain transfer (RAFT) polymerization, employing a tetra-functional xanthate as the RAFT agent, in which the stabilizing groups are linked to the core. These novel star-like RAFT agents induced living/controlled behavior in both the vinyl acetate polymerization at 60 °C and in the vinyl propionate polymerization at 90 °C, respectively, leading to star polymers with minimum polydispersities of 1.2 and maximum apparent number average molecular weights of about 50,000 g·mol^-1. The microstructure of the star polymers was confirmed by electrospray ionization mass spectrometry.     

Morpholine‐based RAFT agents for the reversible deactivation radical polymerization of vinyl acetate and N‐vinylimidazole

Reversible addition–fragmentation chain transfer (RAFT) polymerization of less‐activated monomers in a controlled fashion is challenging due to the high reactivity and instability of the propagating radicals. We have designed dithiocarbamate‐based RAFT agents with morpholine as activating ‘Z’ group and benzyl, ethyl(1‐ethanoate)yl, ethyl(2‐propanoate)yl and cyanomethyl as ‘R’ leaving groups and investigated them for the reversible deactivation radical polymerization of vinyl acetate (VAc) and N‐vinylimidazole (N‐VIm). RAFT polymerization of VAc and N‐VIm at 70 °C using azobisisobutyronitrile as a free radical initiator proceeded in a controlled fashion as demonstrated by a linear increase in molar mass with conversion. Interestingly, the polymerization of VAc followed fast kinetics (approx. 60 min) with good to moderate control affording high‐molar‐mass poly(VAc) polymers. Furthermore, the synthesized chain transfer agents were able to polymerize N‐VIm under controlled conditions. The morpholine RAFT agents bearing cyanomethyl and ethyl(2‐propanoate)yl leaving groups showed better control of the polymerization of VAc and N‐VIm compared to the others. © 2020 Society of Chemical Industry     

纤维素自组装材料的研究进展

纤维素自组装材料具有可再生、生物相容性好、可生物降解且力学性能高的优点,是最有潜力的绿色材料之一。纤维素及其衍生物可直接与第二组装单体构筑纤维素自组装材料,也可利用化学修饰研究改性后的纤维素及衍生物的自组装行为,其中改性处理是最主要的构筑方式。本文着重介绍了纤维素及纤维素衍生物的改性与自组装,对比分析了长碳链疏水化、乙烯基类单体原子转移自由基聚合、脂肪族聚酯单体开环聚合、氨基酸单体可逆-加成断裂链转移聚合改性合成组装分子的原理与特点,综述了组装分子在水体系和非水体系中构筑纤维素自组装材料的最新研究状况,指出纤维素及纤维素衍生物改性后构筑的组装材料具有智能响应性,可通过外界环境变化（如温度、pH、CO₂等）调节纤维素自组装形态,在药物控释、生物传感器及生物膜材料方面有潜在的应用价值;最后对纤维素自组装材料的可增长点进行了展望。     

Synthesis of Chain-end Functionalized Polyolefins and Polyolefin Diblock Copolymers via the Combination of Metallocene Catalysts and Reactive Chain Transfer Agents

This paper discusses a facile route to prepare chain-end functionalized polyolefins containing a terminal functional group (OH, COOH, NH₂, etc.), and polyolefin diblock copolymers containing a polyolefin block and a functional polymer block. The chemistry is centered at an in situ chain transfer reaction during metallocene-mediated α-olefin polymerization using two reactive chain transfer (CT) agents, including dialkylborane (R₂B-H) and styrenic molecule/H₂, to form polyolefin containing a reactive alkylborane and styrenic terminal group, respectively. With the appropriate choice of metallocene catalyst, the polymer formed shows narrow molecular weight distribution (M_w/M_n∼2), and the polymer molecular weight is inversely proportional to the molar ratio of [CT agent]/[α-olefin]. In turn, the terminal borane group is very versatile in interconversion to various polar groups. More importantly, it can be quantitatively transformed to a living radical initiator for chain extension reaction with functional monomers. On the other hand, the terminal styrenic group was then selectively metallated and transformed to a stable polymeric anion for living anionic polymerization. The overall diblock co-polymer process resembles a transformation reaction from metallocene-mediated α-olefin polymerization to a living free radical or a living anionic polymerization of functional monomers.     

纳米纤维素晶须表面接枝及其液晶性能研究进展

作为一种新兴的纳米生物材料,纳米纤维素日益受到各界的广泛关注,对其进行表面接枝改性并开发新的功能是十分必要的。本文综述了纳米纤维素晶须表面接枝的技术及研究进展,主要介绍了传统自由基聚合、离子和开环聚合及活性自由基聚合技术,包括氮氧自由基调控活性聚合、原子转移自由基聚合、可逆加成-断裂链转移聚合、单电子转移活性自由基聚合,讨论了各种接枝聚合方法的适用范围和优缺点。简述了点击化学在纳米纤维素晶须表面接枝的应用。通过各种聚合方法改性得到的纳米纤维素晶须接枝共聚物往往具有一些特殊的功能,某些接枝共聚物在适当的溶剂中可以形成液晶态,本文重点介绍了接枝改性的纳米纤维素晶须的液晶性能及其形成机理和影响因素等。