甲基丙烯酸2-N,N-二甲氨基乙酯与甲基丙烯酸甲酯的氧化共聚合的机理研究

研究了CuCl/五甲基二亚乙基三胺(PMDETA)催化的甲基丙烯酸2-N,N-二甲氨基乙酯(DMAEMA)与甲基丙烯酸甲酯(MMA)在氧气存在下的氧化共聚合,通过改变单体配比、催化剂浓度和反应温度对实验条件进行研究.结果显示,在本实验中的单体配比([DMAEMA]∶[MMA]=10∶0～5∶5)、催化剂浓度([CuCl/PMDETA3]=3.1×10-5 mol/L～6×10-3 mol/L)和反应温度(30～80℃)下,聚合均可以顺利发生,而且聚合过程中单体转化率和所得聚合物的分子量都随着反应进行而增加,且分子量呈现宽分布.1H-NMR结果显示所得聚合物中含有DMAEMA和MMA的单体单元.DSC结果显示所得聚合物是一个部分相容体系.利用此方法所得的PDMAEMA进行MMA的原子转移自由基聚合(ATRP)扩链过程则证实,所得聚合物具有C—Cl末端官能团.由此可以认为,在以上过程中,O2先将CuCl氧化成[Cu(Ⅱ)Cl]+,[Cu(Ⅱ)Cl]+再将二甲胺基氧化成N—CH2.自由基,N—CH2.自由基与[Cu(Ⅱ)Cl]+构成反向ATRP体系,从而得到以C—Cl为末端的聚合物.     

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.     

N,N-二乙基硫代氨基甲酰硫基团(S_2CNEt_2)为假卤原子转移的原子转移自由基聚合新体系

综述了原子转移自由基聚合 (ATRP)中 ,以N ,N 二乙基硫代氨基甲酰硫基团 (S2 CNEt2 )转移实现活性聚合、控制聚合物结构的 4种新方法 :非卤化物 ,N ,N 二乙基二硫代氨基甲酸亚铜 [Cu(S2 CNEt2 ) ]催化甲基丙烯酸甲酯 (MMA)的正向ATRP ;2 ,2′ 联吡啶存在的条件下 ,过氧化苯甲酰 (BPO)与Cu(S2 CNEt2 )的氧化还原反应控制MMA的本体反向ATRP;同时含可转移卤原子、基团的氯化二乙基二硫代氨基甲酸铜 [Cu(S2 CNEt2 ) Cl]成功地用于偶氮二异丁腈或BPO引发的乙烯类单体反向ATRP.假卤原子S2 CNEt2 转移的ATRP得到窄分布的精确结构聚合物分子链ω 端含有光敏基团S2 CNEt2 ,可引发乙烯类单体的常温光聚合 ,实现ATRP与光聚合相结合制备嵌段共聚物     

溶剂热体系中甲基丙烯酸甲酯的原子转移自由基聚合

以FeCl3/ PPh3为催化体系,在无引发剂、溶剂热体系中进行甲基丙烯酸甲酯(MMA)的原子转移自由基聚合(ATRP)反应.考察了反应温度与还原剂对反应的影响.实验结果表明,在溶剂热体系中进行的MMA聚合反应符合"活性"/可控聚合,聚合过程中转化率和分子量随时间的增加而增大,所得聚甲基丙烯酸甲酯分子量分布较窄.     

氯丁胶乳乳液接枝甲基丙烯酸甲酯的反应动力学

采用乳液聚合法将甲基丙烯酸甲酯(MMA)接枝到氯丁胶乳上,红外光谱和核磁共振氢谱证实了接枝产物的生成。 研究了反应温度、乳化剂浓度、引发剂浓度和单体浓度对表观聚合速率的影响。 结果表明,当反应温度为50 ℃,引发剂叔丁基过氧化氢 四乙烯五胺（t-BHP/TEPA）用量为氯丁胶乳干重的0.5%,单体/聚合物质量比m(M)∶m(P)=3∶5,乳化剂十二烷基连苯醚二磺酸钠（DSB）用量为单体总质量1%时,单体转化率和接枝效率分别为99.1%和54.9%。 聚合反应动力学关系式为：Rp=Kc(E)0.15c(I)0.30c(MMA)1.41,式中,K为常数,在40~55 ℃范围内,聚合反应的表观活化能Ea＝60.2 kJ/mol。 接枝聚合基本符合自由基反应机理。     

氯丁胶乳乳液接枝甲基丙烯酸甲酯反应动力学

采用乳液聚合法将甲基丙烯酸甲酯(MMA)接枝到氯丁胶乳上,红外光谱和核磁共振氢谱证实了接枝产物的生成。研究了反应温度、乳化剂浓度、引发剂浓度和单体浓度对表观聚合速率的影响。结果表明,当反应温度为50℃,引发剂叔丁基过氧化氢-四乙烯五胺(t-BHP/TEPA)用量为氯丁胶乳干重的0.5%,单体/聚合物质量比m(M):m(P)=3:5,乳化剂十二烷基连苯醚二磺酸钠(DSB)用量为单体总质量1%时,单体转化率和接枝效率分别为99.1%和54.9%。聚合反应动力学关系式为:Rp=Kc(E)0.15c(I)0.30c(MMA)1.41,式中,K为常数,在40～55℃范围内,聚合反应的表观活化能Ea=60.2kJ/mol。接枝聚合基本符合自由基反应机理。     

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.     

氢氧根对苯乙烯和甲基丙烯酸甲酯ATRP悬浮共聚的影响

在85℃下,以α-溴异丁酰溴为引发剂、氯化亚铜为催化剂、2,2′-联吡啶(bpy)为配体,研究了氢氧化钠(NaOH)含量对苯乙烯和甲基丙烯酸甲酯的原子转移自由基悬浮共聚合的影响。1H-NMR分析和共聚竞聚率(rSt=0.83,rMMA=0.82)表明St/MMA原子转移悬浮共聚容易形成恒比共聚。ATRP的悬浮聚合表现出较好的可控/活性特征。在试验水相中氢氧根浓度为0至3%的范围内,单体转化率、ln[M]0/[M]和表观反应速率常数kappp都随着氢氧根浓度增大而增大。氢氧根并不影响聚合反应的一级动力学特征,但具有加速St/MMA原子转移悬浮共聚反应的作用。探讨了氢氧根在St/MMA原子转移悬浮共聚反应中的作用机理。     

酶催化原子转移自由基聚合

原子转移自由基聚合(ATRP)是制备分子量以及分散度可控聚合物的重要途径。然而,受制于除氧步骤复杂、金属催化剂残留以及单体适用范围有限等因素,ATRP难以应用于批量制备功能化聚合物/共聚物材料,限制了其进一步应用。近年来提出和发展的酶催化聚合,为高效便捷除氧、拓展单体适用范围以及制备具有特殊(纳米)结构的纯净聚合物/共聚物提供了新思路。本文详细介绍了酶的结构与催化机理,以酶的种类进行分类,系统总结了具有不同结构的酶催化体系(包括过氧化辣根酶、血红蛋白、血红素、漆酶等)的催化机理、适用单体、优缺点及应用等;综述了酶以及酶模拟物催化ATRP体系的发展现状;最后,对酶催化ATRP的发展前景和挑战进行了探讨和展望。     

采用ATRP合成天然橡胶接枝共聚物——Ⅲ.NR-g-PMMA的制备

N-溴代丁二酰亚胺与天然橡胶(NR)反应合成了大分子引发剂——溴代天然橡胶[NR-Br(1)].通过原子转移自由基聚合(ATRP),以CuBr/PMDTA为催化体系,1引发甲基丙烯酸甲酯(MMA)接枝共聚制得新型天然橡胶-g-聚甲基丙烯酸甲酯[NR-g-PMMA(2)],其结构经1H NMR和IR表征.初步聚合反应动力学研究结果表明,NBS与NR在高温下反应容易伴随双键加成和环化反应,于室温反应所得1具有较高的引发活性;接枝聚合符合一级动力学反应,即2的分子量随MMA单体转化率的提高而增加.     

Monochelic Versus Telechelic Poly(Methyl Methacrylate) as a Matrix for Photoluminescent Nanocomposites with Quantum Dots

Nanocomposites based on CdSe or CdSe/ZnS quantum dots (QDs) and poly(methyl methacrylate) (PMMA) of different molecular weights and functionality were synthesized by ligand exchange of oleic acid with RAFT-based PMMA. The successful ligand exchange was confirmed by dynamic light scattering in combination with the approach “macromolecules—ghosts” and transmission electron microscopy. Comparative study of mono- and telechelics of PMMA revealed the similarities and differences in their behavior in formation of complexes with QDs and the optical properties of the corresponding nanocomposites. Telechelics exhibited higher efficiency in the complex formation and seemed to be promising candidates for the construction of devices based on QDs and polymer matrix for optical applications.     

New σ-μ ligands for the anionic polymerization of methacrylates in apolar medium

Poly(methyl methacrylate) (PMMA) has been anionically synthesized at high temperature and in apolar media, using diphenylhexyllithium (DPHLi) as initiator and a novel σ-μ chelating ligand to curb the side reactions. It has been indeed found that lithium 2-(dimethylamino-)ethoxide is a very efficient σ-μ ligand that prevents the anionic polymerization of methyl methacrylate (MMA) from being disrupted by significant secondary termination reactions. Ligand/initiator molar ratio, solvent polarity, temperature, monomer and active center concentrations are proved to be key parameters in the control of the polymerization process.     

ARGET ATRP of methyl methacrylate with 2-(8-heptadecenyl)-4,5-dihydro-1H-imidazole-1-ethylamine (OLC) as both ligand and reducing agent in the presence of air

Copper(II)-mediated activators regenerated by electron transfer for atom transfer radical polymerization of methyl methacrylate (MMA) was successfully carried out in a limited amount of air in the presence of 2-(8-heptadecenyl)-4,5-dihydro-1H-Imidazole-1-ethylamine as ligand that served not only as ligand but also as reducing agents. Reduction of Cu(II) to Cu(I) by an excess amount of nitrogen-based ligand was followed by UV–visible spectroscopy. The kinetics of the polymerizations and effect of different polymerization conditions are investigated. It is found that the polymerization of MMA can be conducted well even if the amount of Cu(II) is as low as 1 mol% catalyst relative to initiator. The results of the polymerizations demonstrate the features of “living”/controlled free-radical polymerization, such as the number-average molecular weights being close to their corresponding theoretical values and increasing linearly with monomer conversion, and narrow molecular weight distributions. Chain extension of poly(methyl methacrylate)s with MMA was successful and demonstrated well-maintained end-group functionality.     

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。     

Fluorinated and ring‐substituted bisbenzimidazole copper complexes for ethylene/acrylate copolymerization

Bisbenzimidazole copper dichloride complexes (CuBBIMs), when activated with methylaluminoxane, catalyze the random copolymerization of ethylene with acrylates to produce highly linear functional copolymers. To probe the sensitivity of the copolymerization to the catalyst structure, a series of CuBBIM catalysts with various steric, electronic, and geometric ligand characteristics was prepared, including CuBBIMs having benzimidazole ring substituents and ligand backbones of various lengths. Four different acrylates were also evaluated as comonomers (t‐butyl acrylate, methyl acrylate, t‐butyl methacrylate, and methyl methacrylate). Although no obvious ligand‐based influences on copolymerization were identified, the structure of the acrylate comonomer was found to exert significant effects. Copolymers prepared with t‐butyl methacrylate comonomer exhibited the highest ethylene contents (31–63%), whereas those prepared with methyl acrylate contained only minor amounts of ethylene (<15%). Copolymerizations carried out at lowered acrylate feed levels generally had increased ethylene contents but showed smaller yields, lowered molecular weights, and increased branching. Unusual ketoester structures were also observed in the methyl acrylate and methyl methacrylate containing copolymers, suggesting that the acrylate ester group size may be an important controlling factor for copolymerization. © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 1817–1840, 2006     

Polymerization of Methyl Methacrylate with Ni(II) α‐Diimine/MAO and Fe(II) and Co(II) Pyridyl Bis(imine)/MAO

Polymerizations of methyl methacrylate with (α‐diimine)nickel(II)/methylaluminoxane (MAO) and (pyridyl bis(imine))iron(II) and (pyridyl bis(imine))cobalt(II)/MAO are reported. Effects of structural variation of the ligand on the activities of catalysts and polymer microstructure are described. The catalyst systems gave syndio‐rich poly(methyl methacrylate). The α‐diimine system showed much higher activity than the pyridyl bis(imine) systems under similar polymerization conditions.

     

Investigation of infrared calibration methods for application to the study of methyl methacrylate polymerization

Infrared spectroscopy has been used to monitor the polymerization of methyl methacrylate. Concentrations of methyl methacrylate in the reaction mixture were determined by use of three calibration methods. Classical quantitative analysis was used to measure the height of the stretching vibration bands of the vinyl group at 1639 cm(-1). A calibration procedure using the considerably higher intensity of the C = O stretching vibration band of the carbonyl ester group at 1725 cm(-1) seemed useful only for high concentrations of methyl methacrylate, i.e. at the beginning of reaction, because this band overlaps that of poly(methyl methacrylate). Use of second-derivative spectra and measuring their values at 1725 cm(-1) enabled estimation of ten times lower concentrations of methyl methacrylate the calibration using the band from the vinyl group.     

Synthesis and fluorescence property of terbium complex with novel schiff-base macromolecular ligand

Novel schiff-base macromolecular ligand was synthesized by copolymerizing schiff-base monomer, methyl methacrylate and ethyl acrylate. New polymeric materials based on terbium complex with this macromolecular ligand were prepared. The fluorescence properties of the terbium-complex polymer were investigated experimentally. The new polymeric materials developed herein exhibit the characteristic fluorescence properties of the terbium(III) ion, making them applicable in a wide range of new technologies.     

Atom Transfer Radical Polymerization of Methyl Methacrylate Using Telechelic Tribromo Terminated Polyurethane Macroinitiator

Novel telechelic tribromo terminated polyurethane (Br₃-PU-Br₃) was used as a macroinitiator in atom transfer radical polymerization (ATRP) of methyl methacrylate using CuBr as a catalyst and NN,N',N”,N”-pentamethyldiethylenetriamine (PMDETA) as a ligand. During the course of polymerization, poly(methyl methacrylate)-b-polyurethane-b-poly(methyl methacrylate) (PMMA-b-PU-b-PMMA) tri-block copolymers were formed. The resulting tri-block copolymers were characterized by gel permeation chromatography (GPC) and ¹H nuclear magnetic resonance (NMR) spectroscopy. Molecular weight of the tri-block copolymers increases with increasing conversion. This result shows Br₃-PU-Br₃/CuBr/PMDETA initiating system polymerized methyl methacrylate through ATRP mechanism. NMR spectroscopy results revealed that apart from bromine atom transfer from Br₃-PU-Br₃ to PMDETA-CuBr complex, bromine atom transfer from the initially formed tri-block copolymer to PMDETA-CuBr complex also takes place, and, as a result, double bond terminated copolymer formed. Mole ratio of polyurethane and poly(methyl methacrylate) present in the PMMA-b-PU-b-PMMA tri-block copolymers was calculated using ¹H-NMR spectroscopy and it was found to be comparable with the mole ratio calculated through GPC results. Differential scanning calorimetric results confirmed the presence of two different phases in the tri-block copolymers.     

机理转移法合成星形梳状聚丁二烯-g-聚甲基丙烯酸甲酯共聚物的研究

结合活性负离子聚合与原子转移自由基聚合(ATRP),采用机理转移法制备了一系列窄分布且分子量可控的星形梳状聚丁二烯-g-聚甲基丙烯酸甲酯接枝共聚物(SC-(PB-g-PMMA)).首先通过阴离子聚合,制备星形聚丁二烯,后经甲酸-过氧化氢原位环氧化对链中部分双键进行环氧化,再与原位生成2-溴异丁酸发生酯化反应,得到具有链中活性溴的星形大分子引发剂(SPB-Brn).然后,利用该大分子引发剂,采用CuCl/CuCl2/PMDETA催化体系,通过ATRP聚合单体MMA,合成出星形梳状SC-(PB-g-PMMA)聚合物.通过GPC,1H-NMR和FTIR等分析手段对合成的星形大分子引发剂及星形梳状聚合物进结构表征,证实得到目标产物,并同时研究了聚合物的热力学性质与溶液性质.