新引发体系引发MMA活性自由基聚合

近年来 ,关于活性自由基聚合的研究极为活跃 ,已经发现了多种基于增长链自由基被可逆钝化形成休眠种的活性自由基聚合方法[1,2 ] .它们主要包括引发转移终止剂 ( Iniferter) ,稳定自由基聚合( SFRP) ,原子转移自由基聚合 ( ATRP) ,可逆加成 -断链链转移聚合 ( RAFT)等 .其中 ATRP因其具有可聚合单体多 ,反应条件相对缓和等优点而成为该领域的研究热点 [3～ 5] .ATRP活性自由基聚合的实现主要是在过渡金属催化剂的作用下 ,通过循环往复的碳 -卤键的活化、加成、碳 -卤键的再形成而得到最终活性的聚合物 ,引发体系由引发剂、过渡金属…     

一种反向原子转移自由基聚合引发体系

提出了一种反向原子转移自由基聚合(RATRP)引发体系EB iB/SnC l2.2H2O/FeC l3.6H2O。实验发现,EB iB/SnC l2.2H2O与不同配体络合后,均能引发甲基丙烯酸甲酯(MMA)聚合,但引发效率小于10%,所得聚合物的分子量分布较宽(Mw/Mn>2.0)。当加入FeC l3.6H2O后,引发效率大大提高(>80%),聚合速度明显加快,所得聚合物的分子量分布明显变窄(Mn/Mw<1.28),体系呈现活性聚合特征。分别考察了以N,N,N,’N,”N”-(五丙烯酸甲酯基)二乙烯三胺(MA5-DETA)和三苯基膦(PPh3)为络合剂时,EB iB/SnC l2.2H2O/FeC l3.6H2O催化MMA的本体和溶液聚合的规律并探讨了引发机理。     

CuX／bpy催化体系中甲基丙烯酸甲酯的原子转移自由基聚合

讨论了以α－溴代丙酸乙酯（ＥＰＮ－Ｂｒ）为引发剂、卤化亚铜（ＣｕＸ）／联二吡啶（ｂｐｙ）为催化剂，８０℃下，甲基丙烯酸甲酯（ＭＭＡ）地不同溶剂中的原子转移自由基聚合（ＡＴＲＰ）反应。通过对催化剂ＣｕＢｒ或ＣｕＣｌ及几种溶剂的考察，发现在８０℃下ＥＰＮ－Ｂｒ／ＣｕＢｒ／ｂｐｙ能有效控制丙烯酸甲酯（ＭＡ）的本体ＡＴＲＰ反应，但并不能很好地控制ＭＭＡ在ＥＡｃ中的聚合反应为一可控聚合过程，引发效率为０．８     

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.     

负载卤化镍(NiX2/HD)催化MMA的原子转移自由基聚合

以负载卤化镍(NiX2/HD)为催化剂合成聚甲基丙烯酸甲酯(PMMA),具有反应可控、后处理简单且催化剂可以反复使用的优点。研究结果表明:卤原子、催化剂、钝化剂的类型和含量、反应温度等条件对该体系的聚合速率及可控性有重要影响。在相同条件下,NiCl2较NiBr2的催化速率快;钝化剂卤化铜/三-(N,N-二甲基氨基乙基)胺(CuX2/Me6TREN)对聚合产物分子量分布的可控性要优于卤化铁/三-(N,N-二甲基氨基乙基)胺(FeX3/Me6TREN);增大钝化剂的含量,聚合速率降低,且含量为1%时聚合的可控性较好;温度升高聚合速率加快,分子量分布指数(PDI)增大。顺磁共振检测中观察到钝化剂中过渡金属的化合价发生改变。     

原子转移自由基聚合研究进展

原子转移自由基聚合(Atom transfer radical polymerization,ATRP)是一种发展较快的可控/活性聚合技术,现已广泛应用于聚合物分子结构设计及众多功能高分子材料的合成.本文在综述了ATRP的反应机理的基础上,介绍了引发剂、催化剂、配体、单体等对ATRP的影响,同时综述了降低(或去除)金属盐含量的绿色、高效ATRP聚合体系,如引发剂持续再生活化ATRP,电子转移生成(再生)活化剂ATRP,铁催化体系,光催化体系等.近年来发展的无金属光诱导的有机催化ATRP聚合体系也做了综述.     

异丙醇铝改进的原子转移自由基聚合催化体系

以α 溴代异丁酸乙酯［２ （ＥｉＢ） Ｂｒ］ 为引发剂,溴化亚铜（ＣｕＢｒ）／ 联二吡啶（ｂｐｙ）／ 异丙醇铝［Ａｌ（ＯｉＰｒ）３］ 为复合催化剂,在环己酮溶液中进行了甲基丙烯酸正丁酯（ＢＭＡ） 的原子转移自由基聚合（ＡＴＲＰ） ．研究了异丙醇铝对聚合速率及产物分子量分布的影响．异丙醇铝可与引发剂和聚合物中的羰基配位,使相邻的Ｃ—Ｂｒ 键活化,ＡＴＲＰ 反应可以在较低温度下进行．适量溴化铜的加入,可调节ＡＴＲＰ 活性,可得到分子量可控且分子量分布窄的ＰＢＭＡ（ ＭＷＤ＝ １－３ ～１－５） ．     

苯乙烯与富马酸二甲酯的原子转移自由基无规共聚

2-溴丙酸乙酯(EBP)为引发剂,CuBr为催化剂,N,N,N′,N″,N″-五甲基二亚乙基三胺(PMDETA)为配位剂的富马酸二甲酯(DMF)与苯乙烯(St)的原子转移自由基无规共聚合,转化率低于60％时,1n([M]0／[M])随聚合时间线性增加,数均分子量(Mn)随转化率性增长,所得聚合物分子量分布(PDI)较窄。根据元素分析所得共聚物的平均组成,由Kelerr—Tudos方程,计算两种共聚单体的竞聚率分别是rst=0．488,rDMF=0．303。并探讨了单体与引发剂配比以及温度对聚合反应的影响。     

甲基丙烯酸甲酯的反向原子转移自由基聚合反应 研究

在较低的温度(60℃)和较低的AIBN/CuCl~2/配位剂摩尔比(1:2:4)条件下,用乙腈为溶剂,实现了甲基丙烯酸甲酯(MMA)的反向原子转移自由基聚合(RATRP)。联二吡啶(bpy)为配位剂时,所合成的聚甲基丙烯酸甲酯(PMMA)的分子量分布可低至1.08。用1,10-菲咯啉(phen)代替bpy,MMA的聚合反应速率加快,但其分子量分布稍宽(1.40左右),并进一步研究了bpy和phen作为混合配位剂时对MMA反向ATRP聚合的影响。用RATRP反应所得的带有卤素端基的PMMA作为苯乙烯ATRP的大分子引发剂,成功地合成了具有预期结构的苯乙烯与甲基丙烯酸甲酯嵌段共聚物,大分子引发剂的引发效率接近于1,说明在RATRP过程中由自由基引发剂引发MMA进行一般自由基聚合反应的可能性甚微。     

氨基酸希夫碱铜(Ⅱ)催化MMA原子转移自由基聚合的研究

分别以L-蛋氨酸和L-组氨酸为原料,与水杨醛通过缩合反应合成了两个氨基酸水杨醛希夫碱铜(Ⅱ)配合物(1a和1b).以1为催化剂,2-溴异丁酸乙酯为引发剂,进行甲基丙烯酸甲酯(MMA)的原子转移自由基聚合制得聚甲基丙烯酸甲酯(PMMA),其立构规整度由13C NMR测定.实验结果表明,PMMA数均分子量随MMA转化率线性...     

新型引发体系引发MMA"活性"自由基聚合

传统的原子转移自由基聚合(ATRP)引发体系是由卤化物(引发剂)、低价过渡金属和合适的配体组成的络合物(催化剂)[1,2],即RX/Mnt/LX,三部分组成的.但由于卤化物的毒性和低价过渡金属易被空气中的氧气氧化,因此Matyjaszewski等[3,4]和Teyssié等[5]提出了新的引发体系反向ATRP.反向ATRP用传统引发剂(如AIBN)代替卤化物,用高价过渡金属络合物代替原来的催化体系,即AIBN/Mn+1t/LX,就避免了上述两个缺点.反向ATRP的引发反应机理表述如下:　　目前已见诸报道的关于反向ATRP的文献甚少[3～5],所使用的引发剂均为AIBN.Wang和Matyja…     

SYNTHESIS OF POLY(METHYL METHACRYLATE)-graft-POLYSTYRENE BY ATOM TRANSFER RADICAL POLYMERIZATION

The radical copolymerization of methyl methacrylate and 2-hydroxyethyl methacrylate was carried out via atomtransfer radical polymerization (ATRP) initiated by ethyl 2-bromoisobutyrate and catalyzed by CuBr/2,2'-bipyridinecomplex. This polymerization proceeds in a living fashion with controlled molecular weight and low polydispersity. Theobtained copolymer was esterified with 2-bromoisobutylryl bromide yielding a macroinitiator, poly(methyl methacrylate-co-2-hydroxyethyl methacrylate-co-2-(2-bromoisobutyryloxy)ethyl methacrylate), and its structure was characterized by ~1H-NMR. This macroinitiator was used for ATRP of styrene to synthesize poly(methyl methacrylate)-graft-polystyrene. Themolecular weight of graft copolymer increased with the monomer conversion, and the polydispersity remained relatively low.The individual grafted polystyrene chains were cleaved from the macroinitiator backbone by hydrolysis and the hydrolyzed product was characterized by ~1H-NMR and GPC.     

茂金属化合物/Zn/BDGE/MAO催化体系合成aPS-b-P(S-co-E)-b-PE嵌段共聚物的研究

采用单茂钛化合物CpTiCl3,有机环氧化合物1,4-丁二醇二缩水甘油基醚(BDGE),金属锌(Zn)及甲基铝氧烷(MAO)为催化体系,通过自由基聚合和配位聚合机理合成无规聚苯乙烯-b-聚(苯乙烯-co-乙烯)-b-聚乙烯(aPS-b-P(S-co-E)-b-PE).探讨了温度、时间、乙烯压力及Al/Ti摩尔比对共聚合的影响.所得嵌段共聚物采用DSC,WAXD,GPC和13C-NMR等手段进行了表征.结果表明该共聚物是苯乙烯/乙烯嵌段共聚物,聚苯乙烯链段是无规的,聚乙烯链段具有结晶性.     

原子转移自由基聚合制备聚(甲基丙烯酸甲酯-b-苯乙烯)时单体聚合顺序对嵌段效率的影响

采用原子转移自由基聚合研究了聚（ 甲基丙烯酸甲酯 ｂ 苯乙烯） 嵌段共聚物的合成,实验结果表明,当先进行甲基丙烯酸甲酯的聚合,然后再进行苯乙烯的聚合时,得到了完全的嵌段共聚物;反之,如果改变单体的聚合顺序,则嵌段效率很低．用聚合物末端Ｃ—Ｘ（Ｘ＝ Ｃｌ,Ｂｒ） 键的断裂能对实验结果进行了解释．     

AGET ATRP of methyl methacrylate with poly(ethylene glycol) (PEG) as solvent and TMEDA as both ligand and reducing agent

Activator generated by electron transfer atom transfer radical polymerization of methyl methacrylate (MMA) in inexpensive, non-toxic poly(ethylene glycol) (PEG), with air-stable Cu(II)X₂(X = Br, Cl) as the catalyst and N,N,N′,N′-tetramethylethylenediamine (TMEDA) as both ligand and reducing agent was investigated. The polymerizations in PEG proceeded in a well-controlled manner as evidenced by kinetic studies and chain extension results. The polydispersity of the polymer obtained was quite narrow, with a weight-average molecular weight/number-average molecular weight ratio of less than 1.2. Effects of the TMEDA content and the catalysts on polymerization were also investigated, respectively.     

Novel catalyst system of MCl2/FeCl3·6H2O/PPh3 (M = Ni,Co, or Mn) for the atom transfer radical polymerization of methyl methacrylate

MCl₂ (M = Ni, Co, Sn, or Mn) and PPh₃ together acted as a catalyst for the radical polymerization of methyl methacrylate (MMA) in the presence of ethyl 2‐bromoisobutyrate as an initiator. The four systems all led to conventional radical polymerizations, which yielded polymers with a weight‐average molecular weight/number‐average molecular weight (M_w/M_n) ratio greater than 2.0 and became well controlled when a certain amount of FeCl₃·6H₂O was added. The polymerizations of MMA catalyzed by these four FeCl₃‐modified catalyst systems provided well‐defined polymers with low polydispersities (M_w/M_n < 1.28). © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 43: 2625–2631, 2005     

Initiator‐free atom transfer radical polymerization of methyl methacrylate based on FeBr3(PPh3)n system

A tricomponent system, constituting monomer (methyl methacrylate, MMA), higher oxidation state transition‐metal catalyst (FeBr₃) and a ligand (triphenylphosphine, PPh₃), MMA/FeBr₃/PPh₃ system without external initiator (alkyl halide) has been studied extensively with different spectroscopic analyses. To figure out the mechanism, a series of explicit model reactions were conducted with a molar ratio of [MMA]₀/[FeBr₃]₀/[PPh₃]₀ = 200/1/n (n = 0.1–3.0) at 80 °C, and the corresponding polymerization behaviors were investigated. Combined with theoretical deduction and spectroscopic evidences, the composition of the in‐situ generated initiators was gradually confirmed, which were redox products of FeBr₃ and PPh₃. © 2017 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2017 , 55, 3842–3850     

Cu(PPh3)2BH4作还原剂制备PtCu/C催化剂催化烯烃硅氢 加成反应研究

采用湿法浸渍, Cu(PPh3)2BH4作为还原剂制备了负载型PtCu/C双金属催化剂, Pt∶Cu原子比为0.5～2.0. 用于苯乙烯与三乙氧基硅烷加成反应, Cu元素的引入使Pt/C催化剂的催化性能得到提高, 表现出比Speier催化剂、Karestedt催化剂和Pt/C催化剂更好的β-加成产物选择性. 催化直链烯烃与三乙氧基硅烷加成反应表现出优良的催化性能, 并且催化剂可重复使用.     

Direct synthesis of amphiphilic block copolymers, consisting of poly(methyl methacrylate) and poly(sodium styrene sulfonate) blocks through atom transfer radical polymerization

Amphiphilic block copolymers of methyl methacrylate (MMA) and sodium styrene sulfonate (SSNa) were successfully synthesized via direct atom transfer radical polymerization (ATRP) of SSNa. First, poly(sodium styrene sulfonate) (PSSNa) or poly(methyl methacrylate) (PMMA) macroinitiators were prepared using proper ATRP systems for each case. In some cases, functional initiators, which allow further reactions, were used. The macroinitiators were characterized and further used to synthesize PSSNa/PMMA block copolymers, by using proper solvent combinations, such as N,N-dimethylformamide/water or methanol/water at appropriate volume ratios, in order to ensure solubility of the synthesized amphiphilic copolymers. The molecular weight of the copolymers was determined by gel permeation chromatography, using water as eluent. By using a combination of analytical techniques like ¹H NMR, FTIR and thermogravimetry, the chemical structure and the actual copolymer composition were determined. Since, the block copolymers were soluble in water, forming hydrophilic/hydrophobic domains in aqueous solution, their micellization behavior was further studied by pyrene fluorescence probing.