【作者】 张成裕；

【导师】 王齐；

【作者基本信息】 浙江大学 ， 高分子化学与物理， 2013， 博士

【摘要】 自由基的加成反应,如自由基加成聚合,广泛用于聚合物的合成。自由基的偶合反应是最快的有机反应之一,但是由于自由基的歧化和链转移等副反应的存在,且自由基反应没有选择性,使得自由基偶合反应很少被用于有机和聚合反应。我们报道了一种基于自由基与双键的连续加成-偶合反应,用于制备不同结构的聚合物。α,ω-二溴化合物在铜粉/多元胺作用下,生成碳自由基,与C-亚硝基化合物发生加成反应,原位生成稳定的氮氧自由基与另一碳自由基发生偶合反应。重复以上加成-偶合反应,得到高分子量的聚合物。这一新的聚合方法称为自由基加成-偶合聚合(RACP)。通过凝胶渗透色谱(GPC)研究2,13-二溴代十四烷二酸二甲酯与2-甲基-2-亚硝基丙烷反应产物的分子量随时间的变化。产物的聚合度与反应程度的关系符合Carothers方程,说明该反应的聚合机理为逐步聚合。研究了投料比、副反应、浓度、温度以及单体种类等因素对RACP反应的影响。设计与合成含有不同官能团的二溴化合物,与2-甲基-2-亚硝基丙烷进行RACP反应,制备了具有[AAB]、[ABAC]以及[ABCDCBAD]等重复结构的周期性聚合物,聚合物的主链可含有酯基、酰胺基以及醚键等官能团。由于得到的聚合物中含有C-ON键,因此产物可以进行热降解。另外,RACP反应的中间体齐聚物两端仍然含有溴官能团,可以作为大分子引发剂引发乙烯基单体进行原子转移自由基聚合(ATRP),制备具有新型结构的三嵌段共聚物。α-溴代聚苯乙烯与2-甲基-2-亚硝基丙烷进行RAC反应,得到对称的两段聚苯乙烯,偶合效率接近100%。a,ω-二溴代聚合物与2-甲基-2-亚硝基丙烷进行RAC反应,可制备可降解的多(嵌)段聚合物。通过比较降解前后产物的数均分子量的大小,表明RAC合成的多段聚合物(聚丙烯酸叔丁酯)的嵌段数最高可以达到37。α,ω-二溴代(聚丙烯酸叔丁酯-b-聚苯乙烯-b-聚丙烯酸叔丁酯)(Br-PtBA-b-PS-b-PtBA-Br)与2-甲基-2-亚硝基丙烷反应,可制备多嵌段共聚物(PtBA-b-PS)m。通过2-溴丙酸乙酯、(1-澳十二烷基)苯与1,1-二苯基乙烯反应,研究了自由基加成-交叉偶合(RACC)反应。利用小分子溴化物与α-溴代聚苯乙烯进行RACC反应,实现了聚合物端基官能团的高效转化。两种不同种类的单溴代聚合物(P1-Br和P2-Br)在铜粉/配体的作用下,与双键化合物(X,二硫代苯甲酸乙酯或1,1-二苯基乙烯)发生RACC反应,得到嵌段共聚物Pi-X-P2。RACC反应的交叉偶合效率可以接近95%。更多还原

【Abstract】 Radical addition reaction, such as radical addition polymerization, was widely used in polymer synthesis. Although radical-radical coupling reaction is a kind of rapid reaction with high efficiency, it is scarcely used in organic and polymer synthesis. The reason is that radicals can still undergo disproportionation and transfer reactions besides coupling reaction, which leads to the termination of coupling reactions. We reported a consecutive radical addition-coupling (RAC) reaction to double bonds compounds for preparation of polymers with different structure.The carbon-centered radical generated from a,ω-dibromo dibasic ester promoted by Cu(O)/ligand can be efficiently captured by C-nitroso compound, which results in nitroxide radical. The in-situ formed nitroxide radical immediately undergoes cross-coupling reaction with carbon-centered radical. The alternating copolymers with high molecular weight and unimodal molecular weight distribution can be synthesized by consecutive RAC. This polymerization method was named radical addition-coupling polymerization (RACP). The RACP of dimethyl2,13-dibromotetradecanedioate and2-methyl-2-nitrosopropane was monitored with gel permeation chromatograph (GPC) at various polymerization times. The evolution of molecular weight distribution clearly demonstrated that the polymerization follows the step-growth mechanism. The feed ratio, side-reactions, reaction temperature and monomer concentration, as well as monomer types, affect the results of RACP.The monomer can be well designed, and the polymerization is tolerated to various functional groups. A variety of symmetrical and asymmetrical a,ω-dibromo compounds containing ester, amide, ether or ethylene function groups were subjected to RACP, in order to prepare periodic copolymers possessing [AAB],[ABAC], and [ABCDCBAD] repeating structure. Since alkoxyamine groups are present along the backbone of the RACP product, it can be themodegraded to the precursor. The intermediate polymer prepared by RACP can also be applied as macroinitiator for atom transfer radical polymerization (ATRP) to synthesize triblock copolymer.Monobromo polystyrene was reacted with2-methyl-2-nitrosopropane by RAC reaction to produce the symmetrical polymer with doubled molecular weight (MW) and similar polydispersity index (PDI), which demonstrated that the coupling efficiency is close to100%.The reaction of a,ω-dibromo polymer with a stoichiometric amount of nitroso compounds paved the way to the synthesis of multisegmented polymers. Up to37poly(tery-butyl acrylate)(PtBA) segments constitutes the final product of the reaction of a,ω-dibromo PtBA with2-methyl-2-nitrosopropane, which is the highest block number for a multisegmented polymer prepared by radical coupling. A multiblock copolymer (PtBA-b-PS)m was successfully prepared when the same strategy was applied to a,ω-dibromo poly(tert-butyl acrylate)-b-polystyrene-b-poly(tert-butyl acrylate)(Br-PtBA-b-PS-b-PtBA-Br) precursors.Ethyl2-bromopropionate and (1-bromododecyl)benzene were reacted with1,1-diphenylethylene by radical addition cross-coupling (RACC) reaction. The bromined chain ends of well-defined polystyrene prepared using ATRP were successfully transformed into various functional end groups by RACC. Two different monobromo polymers (P1-Br and P2-Br) were reacted with Cu(0)/ligand in the presence of ethyl dithiobenzoate or1,1-diphenylethylene (X) and the block copolymer (P1-X-P2) can be obtained with high efficiency (up to95%), which cannot be prepared by normal atom transfer radical coupling (ATRC) of mixture of P1-Br and P2-Br.更多还原