【作者】 张丽芬；

【导师】 朱秀林；

【作者基本信息】 苏州大学 ， 高分子化学与物理， 2010， 博士

【摘要】 铜盐催化的电子转移生成催化剂的原子转移自由基聚合（Activators Generated by Electron Transfer for ATRP, AGET ATRP）和引发剂连续再生催化剂原子转移自由基聚合（Initiators for Continuous Activator Regeneration ATRP, ICAR ATRP）是在正向ATRP和反向ATRP的基础上发展起来ATRP新技术。在这些反应体系中仍采用有机卤化物作为引发剂,易保存的高氧化态的过渡金属铜盐（Cu（II））为失活剂,而低氧化态的过渡金属盐催化剂（Cu（I））则在体系中由Cu（II）和还原剂（AGET ATRP）或者常规自由基引发剂（ICAR ATRP）通过氧化还原反应而原位产生。因此催化剂的活性更高,所需的催化剂用量可以大大下降。常规自由基引发剂一般为AIBN,还原剂通常为多糖类有机化合物（如葡萄糖）,维生素C以及异辛酸亚锡等易得、无毒化合物。这些方法还有一些优点,如对AGET ATRP而言,由于还原剂只选择性地与高氧化态的过渡金属盐（Cu（II））反应而不与有机卤化物和单体进行反应,这样在原位产生低氧化态的过渡金属盐的过程中就不会影响到有机卤化物和低氧化态的过渡金属盐（Cu（I））之间的反应。尤其重要的是由于还原剂还可以与反应体系中的氧气导致的过渡金属氧化产物进行反应,因此在进行ATRP聚合之前,只要加入适量的还原剂（去除和氧气反应的消耗量）,则体系则不必像正向和反向ATRP那样事先要对反应体系进行除氧,这对工业过程来说则意义非常。考虑到铁盐催化体系比铜催化体系具有很好的生物相容性,本论文围绕着铁盐催化的AGET ATRP和ICAR ATRP开展了一系列研究工作。主要研究内容包括:采用维生素C（VC）为还原剂,FeCl₃.6H₂O为催化剂,三苯基膦（PPh₃）、亚氨基二乙酸（IDA）以及三-（3,6-二氧庚基）胺（TDA-1）为配体,2-溴异丁酸乙酯（EBiB）、溴化苄（BB）、1,3,5-（2’-溴-2’-异丁酰氧）苯（BMPB）或者α-溴代乙苯（PEBr）为引发剂,以甲基丙烯酸甲酯（MMA）或者苯乙烯（St）为模板单体,首次报道了Fe（III）盐催化的AGET ATRP和ICAR ATRP,并采用端基分析和扩链反应证明了该反应体系的”活性”/可控聚合特征。另外在已掌握的铁盐催化的AGET ATRP规律的基础上,把这一方法应用于在生物领域具有广泛应用前景的碳纳米管的改性,在碳纳米管上可控地接枝上了聚合物壳层。通过对上述体系的研究得到的主要结论如下:（1）采用VC为还原剂,FeCl₃.6H₂O为催化剂,PPh₃为配体,MMA为单体,EBiB为引发剂,N,N-二甲基甲酰胺（DMF）为溶剂,首次报道了Fe（Ⅲ）盐催化的AGET ATRP。该AGET ATRP反应体系在极性溶剂DMF中的反应速率较非极性溶剂甲苯中的要快,但前者对MMA聚合的可控性较后者要差。PMMA的端基分析和扩链反应证明了该反应的”活性”/可控的聚合特征。（2）采用FeCl₃.6H₂O/IDA为催化剂,VC为还原剂,EBiB为引发剂,DMF为溶剂,在空气氛围下进行了MMA的AGET ATRP,建立了以低毒的有机酸为配体的铁盐催化的AGET ATRP反应体系。研究了空气氛围下不同VC用量下的MMA的AGET ATRP的动力学,并提出了空气氛围下铁盐催化AGET ATRP的聚合机理。在有氧条件下的聚合,还原剂VC可以起到很关键的作用。聚合结果表明在相同氧气浓度下,增加VC用量聚合速率加快。（3）以溴化苄为引发剂,FeCl₃·6H₂O为催化剂,PPh₃为配体,VC为还原剂,在110℃研究了铁盐催化体系作用下无氧条件下苯乙烯AGET ATRP本体聚合动力学。聚合物数均分子量随着单体转化率的提高而线性增长,分子量分布比较窄（PDI = 1.14-1.31）,呈现了“活性”/可控聚合特征。（4）建立了以FeCl₃·6H₂O为催化剂,VC为还原剂,TDA-1为配位剂,BMPB为引发剂的铁盐引发体系。该体系催化的苯乙烯的AGET ATRP可以在有限的氧气存在下进行,且表现出了典型的“活性”/可控自由基聚合特征:聚合速率与单体浓度呈一级动力学关系,聚合物的分子量随单体转化率的提高而线性增长并接近相应的理论分子量,且聚合物的分散性指数维持较窄（一般在1.3以下）。另外,该催化体系即使在铁盐用量为引发剂用量5%的情况仍能较好地控制苯乙烯的AGET ATRP,是一个较为高效的铁盐催化体系。（5）建立了以FeCl₃·6H₂O为催化剂,TDA-1为配位剂,PEBr为引发剂,在无常规热引发剂存在条件下的苯乙烯和甲基丙烯酸甲酯的ICAR ATRP体系,提出了热引发ICAR ATRP的聚合机理。研究结果表明,即使三价铁盐的用量降低到50 ppm,苯乙烯的聚合仍能可控。在MMA的聚合中,由于氧分子与MMA单体共聚而成的过氧化物能扮演热引发剂的角色,因此氧气的存在能促进聚合速率提高。（6）建立了以FeCl₃·6H₂O为催化剂,TDA-1为配体,VC为还原剂的铁盐催化的表面AGET ATRP方法。成功地采用该方法在多壁碳纳米管（MWCNTs）接枝上了不同的聚合物。通过TEM证明得到的MWCNTs@PS为核壳结构。经四氢呋喃抽提后的MWCNTs@PS水解去功能化结果以及拉曼光谱都证明了改性的MWCNTs和PS是通过共价键连接的。然而尽管接枝PS的分子量具有可控性,但由于碳纳米管本身结构特点使接枝上的PS的PDI比传统的ATRP得到的PS要宽。更多还原

【Abstract】 Two kinds of novel methods, activators generated by electron transfer for atom transfer radical polymerization （AGET ATRP） and initiators for continuous activator regeneration ATRP （ICAR ATRP） catalyzed by copper, have been developed by combining the advantages of normal ATRP and reverse ATRP. In the two polymerization systems, an alkyl halide is used as an initiator, and a transition metal complex in its oxidatively stable state （Cu（II）） is used as a catalyst. The activators （Cu（I）） with higher activity are produced by the in situ reduction of the copper（II） complexes with nontoxic and easily available glucose, vitamin C （VC）, tin（II） 2-ethylhexanoate （Sn（EH）2） and other reducing agents for AGET ATRP or with a conventional radical initiator such as 2,2’-azobis（isobutyronitrile） （AIBN） for ICAR ATRP. It is noted that the reducing agents do not generate initiating radicals but are exclusively used for the reduction of Cu（II） to Cu（I） activating species for AGET ATRP process. In addition, the reducing agents can simultaneously reduce the oxide of a transition metal complex formed with oxygen to activating species, which makes it possible to conduct AGET ATRP in the presence of a limited amount of air. It will be much important for the industrial process.In this dissertation, a series of works about iron-mediated AGET ATRP and ICAR ATRP were conducted in view of the better biocompatibility and low toxicity of iron catalysts as compared with copper ones. And we reported the iron-mediated AGET ATRPs and ICAR ATRP for the first time using VC as the reducing agent, FeCl₃.6H₂O as the catalyst, triphenylphosphine （PPh₃）, iminodiacetic acid （IDA） and tris（3,6-dioxaheptyl） amine （TDA-1） as the ligands, ethyl 2-bromoisobutyrate （EBiB）, benzyl bromide （BB）, 1,3,5-（2’-bromo-2’-methylpropionato） benzene （BMPB） and （1-bromoethyl）benzene （PEBr） as the initiators, methyl methacrylate （MMA） or styrene （St） as the monomer. End-chain analyses and chain extension experiments confirmed the features of“living”/controlled radical polymerization of the iron-mediated polymerization systems. We also applied the iron-mediated AGET ATRP technique to the surface modification of the carbon nanotubes with potential application as biomaterials, and a controlled polymer layer was grafted onto the surfaces.The following conclusions were drawn according to the detailed studies:1. Iron-mediated AGET ATRP of MMA was first developed using FeCl₃.6H₂O as the catalyst, PPh₃ as the ligand, EBiB as the initiator and VC as the reducing agent. It was found that the polymerization rate in DMF was faster than that in toluene; however, the latter polymerization system had better controllability over the molecular weight and molecular weight distribution than the former. The“living”features of the polymerization system were confirmed by analysis of the chain end and chain extension of PMMA.2. A novel iron-mediated AGET ATRP system in DMF was developed using low toxic organic acid of IDA as the ligand, FeCl₃.6H₂O as the catalyst, EBiB as the initiator, VC as the reducing agent and MMA as the monomer in the presence of a limited amount of air. The kinetics of AGET ATRP of MMA was investigated using different amount of VC in the presence of a limited amount of air, and the plausible polymerization mechanism was drawn correspondingly. The reducing agent VC played a key role for the polymerization of MMA in the presence of a limited amount of air. Increasing the amount of VC increased the polymerization rate of MMA under the same oxygen concentration.3. An iron-mediated bulk AGET ATRP of St was developed using BB as the initiator, FeCl₃·6H₂O as the catalyst, PPh₃ as the ligand and VC as the reducing agent. The kinetics was studied in the absence of oxygen at 110oC. The results showed that the number-average molecular weight of the PS increased with monomer conversion linearly and the molecular weight distribution kept low （PDI = 1.14-1.31）, demonstrating the features of“living”/controlled radical polymerization.4. A highly active iron-based catalyst system for the bulk AGET ATRP of St was obtained using FeCl₃·6H₂O as the catalyst, TDA-1 as the ligand, BMPB as the initiator and VC as the reducing agent in the presence of limited amounts of air. The results of the polymerizations demonstrated the features of‘living’/controlled radical polymerization, such as first order kinetic plot, the number-average molecular weights being close to their corresponding theoretical values and increasing linearly with monomer conversion, and narrow polydispersity indices （PDI = 1.18-1.26）, and the controlled polymerization of St was also obtained even if 5 mol-% of catalyst was used.5. ICAR ATRPs for St and MMA were developed using FeCl₃·6H₂O as the catalyst, TDA-1 as the ligand and PEBr as the initiator in the absence of any thermal radical initiator, and the corresponding polymerization mechanism was provided. The results demonstrated that the polymerization of St could be carried out successfully even if the amount of iron catalyst increased to 50 ppm. In the polymerization of MMA, oxygen was used to form in situ thermal radical initiators, MMA peroxides, which were generated from the interpolymerization of molecular oxygen and MMA monomer; therefore it could enhance the polymerization rate of MMA.6. A surface-initiated AGET ATRP system was developed on the surface of multiwall carbon nanotubes （MWCNTs） using FeCl₃·6H₂O as the catalyst, TDA-1 as the ligand and VC as the reducing agent, and different polymers were successfully grafted onto the surfaces. The core-shell structure of MWCNTs@PS was observed by TEM. Both Raman spectra and the results of hydrolysis of MWCNTs@PS （after extraction by THF） confirmed that the PS chains were covalently tethered onto the surfaces of the MWCNTs. The molecular weights grafted onto the MWCNTs were controlled by the polymerization conditions, but the polydispersity indices were broad （PDI ².0） due to the special structure of the MWCNTs.更多还原