【作者】 徐江涛；

【导师】 杨玉良；

【作者基本信息】 复旦大学 ， 高分子化学与物理， 2006， 博士

【摘要】 可逆加成-裂解链转移（Reversible Addition-Fragmentation chain Transfer，RAFT）自由基聚合方法近十年发展迅速，因其聚合条件温和，单体适应范围广等特点，而广泛应用于嵌段、接枝、超支化和星型等具有特定结构聚合物的合成。本论文以甲基丙烯酸酯类单体的聚合体系为研究对象，研究了该体系的一些特殊机理和动力学，基于我们的实验结果提出了一些全新的观点，分析了RAFT聚合过程中的一些独特的现象。同时采用在单体中引入官能团的方法合成了一系列具有特定结构的均聚物和共聚物，系统全面地研究了它们的聚合动力学，并从合成聚合物结构的角度对聚合物的物理（溶液自组装和宏观相分离等）和化学性质（聚合物稳定性等）进行了研究，清晰地阐明了聚合物的结构和性能之间的关系，并由此提出了这些聚合物的潜力应用。主要内容如下：双硫酯的热稳定性及其对RAFT聚合体系的影响。RAFT阻聚动力学是近几年研究的一个热门课题，主要存在两种截然不同的观点：中间态自由基的交叉终止理论和中间态自由基的慢裂解理论。我们根据合成双硫酯的经验和实验中的观察发现，双硫酯的热稳定性对RAFT聚合影响很大，在较高的温度下双硫酯会发生一定程度的热分解，生成的双硫酸会对聚合有一定的阻聚和延迟作用。我们详细研究了双硫酯的热分解动力学，并考察了它对RAFT聚合体系的影响。RAFT合成聚合物的端基官能化—端基双硫酯的氨解反应。由RAFT聚合的机理可知，聚合最终得到的聚合物的结构包含双硫酯基团，它是聚合物链保持活性特征的重要体现，同时它为聚合物的端基官能化提供了一个重要的途径，其中氨解反应是一个被人们广泛采用的方法，它在很温和的条件下将端基去掉，同时还能将双硫酯端基变成硫醇端基。但是并不是所有的RAFT方法得到的聚合物通过氨解反应得到巯基官能化的聚合物，在我们的工作中发现聚苯乙烯的氨解反应能得到端基巯基，而甲基丙烯酸酯类单体的RAFT聚合物却得到另一种端基—硫代戊内酯（thiolactone）。我们用GPC、MALDI-TOF MS、一维二维NMR、元素分析等方法对氨解过程和氨解产物做了详细的表征。同时我们也提出了一种制备端基巯基的PMMA的实用方法。RAFT方法在具有特定结构聚合物的设计与合成上的应用，在机理研究的基础上，本论文选择五种不同结构的甲基丙烯酸酯类单体：lauryl methacrylate（LMA，L），（N，N-dimethylamino）ethyl methacrylate（DMAEMA，D），poly（ethylene glycol）methyl ether methacrylate（PEGMA，E），4-（4’-cyanobiphenyl-4-yloxy）butyl methacrylate（CBPBMA，C）和2-（cholestryl carbonate）ethyl methacrylate（CCBEMA），用CDB调控RAFT聚合的方法设计合成了一些特定结构的聚合物，详细而深入地研究了它们的均聚、共聚动力学，发现了双硫酯并非在聚合反应初期就全部转化，而是随着反应进行逐步消耗，这与理想的活性聚合体系有很大差别。合成聚合物的结构与性能之间的关系。对RAFT方法设计合成的三种结构的聚合物（季铵化的P（L-b-D）、P（L-ram-D）和P（C-ram-D），分别用P（L-b-D）（+）、PLD（+）、PCD（+）表示）进行了结构与性能关系的研究：（1）P（L-b-D）（+）是一种阳离子型的嵌段共聚物，在水相溶液中会组装成清晰的“核壳”结构的胶束；（2）PLD（+）是一种阳离子型的聚皂，具有聚皂的一些典型特征，在聚合物的表面活性剂、乳化剂、稳定剂、分散剂上有一定的工业意义；（3）PCD（+）也具有聚皂的一些基本特征，但它还具有一些特殊的性质，在混和溶剂THF／H₂O中具有温度敏感特征，具有LCST，改变混和溶剂的组成或者改变聚合物两种单体的组成可以改变LCST值的大小；造成LCST的原因是因为体系升温的时候发生了液-液热致相分离（Thermal-Induced Phase Sepration），存在成核（nucleation）、增长（growth）、粗化（coarsening）和熟化（Ostwald ripening）过程。在相分离后形成大的球形相区后，快速升温会导致二次相分离。更多还原

【Abstract】 Reversible addition-fragmentation chain transfer (RAFT) polymerization is one of the most versatile controlled/"living" radical polymerization techniques due to its compatibility with a wide range of monomers and reaction conditions. It was widely utilized to synthesize well-defined polymers such as block, graft, star and hyperbranched polymers. In this work, we studied the kinetics and mechanism of RAFT polymerization of methacrylates and elucidated one of the possible reasons of retardation effects and inhibition during the RAFT polymerization. Some well-defined block and random copolymers were synthesized by employing some methacrylates with functional groups as the comonomers. We studied the relationship between structures and properties of these synthetic copolymers and prospected their potential applications.First, thermal stability of dithioesters, classical chain transfer agents, and its effect on the RAFT polymerization was investigated. Dithioesters, cumyl dithiobenzoate (CDB) and poly(methyl methacrylate) (PMMA) end-capped with dithioester underwent thermal decomposition at 120℃. The thermal decomposition yielded unsaturated compound and dithiobenzoic acid, leading to some loss of living character of the polymerization, such as retarded reaction rate and broadened molecular weight distribution. Nevertheless, thermal decomposition of 2-(ethoxycarbonyl)prop-2-yl dithiobenzoate, a model compound for PMMA dithioester, does not yield unsaturated product in spite of the resemblance of the chemical structures. Thermogravimetric analysis shows that PMMA dithioesters are more thermally unstable than the other two.Second, aminolysis of polystyrene and poly(methyl methacrylate) (PMMA) prepared by reversible addition-fragmentation chain transfer (RAFT) polymerization was investigated. The product of the former contains predominantly double molecular weight species by the formation of disulfide bond, whereas the latter formed coupled species which consequently cleaved to unimolecular weight species. Matrix-assisted laser desorption inionization time-of-flight mass spectrometry, elemental analysis and NMR indicated that thiolactone terminus was formed after aminolysis of PMMA. We propose that the thiol end-groups generated during the aminolysis of PMMA tend to cyclize through "backbiting" to form thiolactone structure. Similar reaction was observed in the case of poly(N, N-dimethylaminoethyl methacrylate) and poly(laury methacrylate). In spite of this, the preparation of thiol-end functionalized PMMA was achieved by introducing a short block of polystyrene after the RAFT polymerization of MMA.Third, RAFT technique was applied to design and synthesize some well-defined poymers. Five monomers, lauryl methacrylate (LMA, L), (N,N-dimethylamino)ethyl methacrylate (DMAEMA, D), poly(ethylene glycol) methyl ether methacrylate (PEGMA, E), 4-(4’-cyanobiphenyl-4-yloxy) butyl methacrylate (CBPBMA, C) and 2-(cholestryl carbonate)ethyl methacrylate (CCBEMA) were chosen to RAFT homopolymerization or copolymerizations mediated by cumyl dithiobenzoate. The kinetics of polymerizations was comprehensively investigated.Fourth, three kinds of synthetic polymers, quaternized P(L-b-D), P(L-ram-D) and P(C-raw-D) (denoted as P(L-b-D)(+), PLD(+) and PCD(+) ), were synthesized by RAFT technique and their structure-property relationships were studied: (1) P(L-b-D)(+) was a kind of cationic diblock copolymer, which can self-assembly into micelles with core-shell structure. (2) PLD(+), a kind of cationic polysoap, has the typical solution properties of polysoap and could has the potential applications in emulsifier, stabilizer, dispersant and so on. (3) PCD(+) solution in THF/H2O mixed solvent is temperature-responsive due to the thermal-induced phase separation. The phase separation is accompanied by the processes of nucleation, growth, coarsening and Ostwald ripening. The change of temperature would induce secondary phase separation after macro-domain formed.更多还原