【作者】 冉蓉；

【导师】 王跃川；

【作者基本信息】 四川大学 ， 材料学， 2007， 博士

【摘要】 近年来，活性自由基聚合已发展成为高分子化学领域中最具学术意义和工业应用价值的研究方向之一。其领域内颇具影响的体系和方法主要有引发-转移-终止剂(Iniferter)法、稳定自由基聚合(SFRP)法、原子转移自由基聚合(ATRP)法和可逆-加成-断裂链转移(RAFT)法。RAFT“活性”／可控自由基聚合因其集自由基聚合与活性聚合方法的优势于一体而倍受瞩目。自1998年提出以来，获得了长足发展，正发展成为分子设计的强有力工具。然而，目前在这一研究领域中尚存在有待解决的问题，如三硫酯结构与其性能之间关系。针对这一问题，本文尝试用三种方法合成了结构不同的RAFT试剂，考察了热引发、引发剂引发以及紫外光引发条件下，二硫酯／三硫酯调控的常见单体苯乙烯以及(甲基)丙烯酸酯的RAFT聚合。测定了三硫酯的链转移常数；比较了三硫酯对常见单体自由基聚合的控制性能；总结了三硫酯结构与控制性能之间的关系。用量化密度泛函理论对三硫酯的模型化合物进行了计算，根据计算结果对三硫酯的控制性能进行了预测；结果发现理论计算结果与实验结果相互吻合，为设计及合成高效的RAFT试剂探索一种有效的方法。本研究工作的主要研究内容及结果如下：(1)用格氏试剂法合成了二硫代苯甲酸苄酯(BDTB)、二硫代苯甲酸-1-乙酯基-正丙酯(EPDTB)、二硫代苯甲酸(PhCSSH)三种二硫代羧酸(酯)。用相转移法合成了S，S′-二(α，α′-甲基-α″-乙酸)三硫代碳酸酯(TTC1)、S，S′-二丙酸三硫代碳酸酯(TTC3)、S-丙酸-S′-(α-甲基-α′-乙酸)三硫代碳酸酯(TTC4)和S-丙酸-S′-(α，α′-甲基-α″-乙酸)三硫代碳酸酯(TTC5)。首次用阴离子交换树脂法合成了S，S′-二(α-苯乙酮)三硫代碳酸酯(TTC2)。通过FT-IR、NMR和熔点测定对合成的RAFT试剂进行了表征，确定了这些化合物的结构。(2)考察了在热引发、引发剂引发条件下，上述RAFT试剂对苯乙烯(St)、甲基丙烯酸甲酯(MMA)、丙烯酸丁酯(BA)自由基聚合的控制性能，结果表明BDTB、EPDTB、PhCSSH、TTC1、TTC2、TTC4及TTC5调控的聚合反应都显示明显的活性聚合特征；根据分子量分布及IR、NMR分析结果确定TTC1、TTC2、TTC4及TTC5是有效的RAFT试剂。(3)考察了在紫外光引发条件下，五种三硫酯对单体苯乙烯(St)、丙烯酸丁酯(BA)自由基聚合的控制性能，结果表明TTC1、TTC2、TTC4及TTC5在此条件下仍是有效的RAFT试剂。(4)研究了引发剂引发、紫外光引发下的嵌段聚合，并以TTC1、TTC5调控的聚合物PSt-S-C(=S)-S-PSt作为大分子RAFT试剂：分别在紫外光引发、AIBN引发条件下，加入第二种单体(BA)，成功地制备了分子量可控、分子量分布窄(PDI＜1.20)的PSt-PBA-PSt三嵌段共聚物。(5)用密度泛函理论(B3LYP functional using the 6-31G-(d)basis set)对这五种三硫酯的模型化合物进行了计算，得到了三硫酯的键长、键能及断裂形成的自由基的中心碳原子的原子自旋密度等数据，从所得的计算结果预测了合成的三硫酯对RAFT聚合的控制效果，结果发现与实验结果相互吻合。(6)评价了在AIBN引发以及紫外光引发条件下，三硫酯的结构对苯乙烯(St)、丙烯酸丁酯(BA)聚合体系的控制性能。用Mayo方法测定了TTC1、TTC2、TTC4及TTC5在70℃，苯乙烯聚合中的链转移常数。结果显示三硫酯的结构对其控制性能和链转移常数有很大的影响。当在三硫酯中引入共轭结构后可以十分明显的改善其用于苯乙烯自由基聚合的控制性能，决定RAFT试剂可控性的另一个重要因素是R基团离去的难易程度，R基团容易离去，则相应的三硫酯对聚合的可控性越大。更多还原

【Abstract】 Controlled, or "living" free radical polymerization is one of the most importantresearch area in polymer chemistry and polymer preparation, to both academic andpractical researchers in recent years. Four ways to manipulate the free radicalpolymerization have been investigated: Initiation-transfer-termination (Iniferter),nitroxide-mediated polymerization (NMP), atom transfer radical polymerization(ATRP) and reversible addition fragmentation chain transfer (RAFT) process.The RAFT process combines the advantages of both free radical polymerizationand living anionic polymerization. Since its discovery in 1998, it has been receivedmuch more attention and has become a powerful and versatile tool for synthesis ofwell-defined polymers and copolymers with controllable molecular weight, designedarchitectures and functionalized end groups. Although the RAFT has been greatlyimproved, there is still a lot of research need to be done. This research focused on therelationship between chemical structures of RAFT reagents and the controlling ofpolymerization. Dithioester and trithiocarbonate RAFT reagents were synthesizedby different methods, and were used for the polymerization of styrene ormethacrylates, by thermal, thermo-initiator and photo-initiation. The chain transferconstants of the trithiocarbonates were determined. The controlling properties of thetrithiocarbonates were studied and compared with the density functional theorycalculations. It was found that the prediction by calculations for RAFT agents wasquite agreed with the experimental results. The research and main results are outlined as following:(1) Chain transfer reagents, dithiobenzoates, 2-cyanoprop-2-yl dithiobenzoate(BDTB), 1-(ethoxycarbonyl)prop-1-yl dithiobenzoate (EPDTB), and dithiobenzoateacid(PhCSSH) were synthesized by Grignard agent method. TrithiocarbonatesS,S’-bis (α,α′-dimethyl-α" -acetic acid) trithiocarbonate (TTC1),3-(2-carboxyethylsulfanylthiocarbonylsulfanyl) propionic acid (TTC3),2-(2-carboxyethylsulfanylthiocarbonylsulfanyl) propionic acid (TTC4) and2-(2-carboxyethylsulfanylthiocarbonylsulfanyl)-2-methylpropionic acid (TTC5) weresynthesized by phase transfer method. Bis-(2-oxo-2-phenyl-ethyl) trithiocarbonate(TTC2) were synthesized with anion-exchange resin for the first time. The structuresof these compounds were characterized with FT-IR, ~1H-NMR spectra and meltpoint.(2) The controlled free radical polymerizations of styrene (St), methylmethacrylates (MMA) and butyl acrylate (BA), initiated by thermal andthermo-initiator, were investigated using these RAFT agents. It was found that thepolymerization usingBDTB, EPDTB, PhCSSH, TTC1, TTC2, TTC4 and TTC5as RAFT reagent exhibited the characteristics of "living" polymerization.Polymerization kinetics, and the structure of these polymers determined by GPC,FT-IR, ~1H-NMR spectra indicated that TTC1, TTC2, TTC4 and TTC5 are effectiveRAFT agents.(3) The controlled free radical polymerization of styrene (St) and butylacrylate (BA) by photoinitiation with the five trithiocarbonates as RAFT agents wereinvestigated. The four trithiocarbonates TTC1, TTC2, TTC4 and TTC5 are effectiveRAFT agents.(4) Block copolymerizations of St and BA were carried out with initiator andphoto-initiation. The triblock copolymers, PSt-PBA-PSt, with controlled molecularweight and polydispersity, were prepared using PSt-S-C(=S)-S-PSt as themacromolecular initiator.(5) The C-S bond dissociation energies (BDE), C-S bond length and atomicspin densities for radicals were calculated by density functional theory for the fivetrithiocarbonates RAFT reagents compounds. The effects of the five trithiocarbonates on the controlled polymerization were predicted with these data.The calculation results for RAFT agents were agreed with the experimental.(6) The effects of the structure of trithiocarbonates on the controlledpolymerization of styrene, butylacrylate, initiated by AIBN and photoinitiation wereevaluated. The chain transfer constants of TTC1、TTC2、TTC4 and TTC5 in freeradical polymerization of styrene at 70℃were determined using Mayo’s method.The results exhibit that the structure of trithiocarbonatcis has influence on the controlability. The controlling ability for styrene RAFT polymerization is better when aconjugation group connected to the trithiocarbonate. In addition, the leaving group Rin the trithiocarbonate also affects the controlling. With secondary and tertiary alkylleaving groups the trithiocarbonates will exhibit better controlling on molecularweight and polydispersities in free radical polymerization.更多还原