【作者】 林文程；

【导师】 黄骏廉；

【作者基本信息】 复旦大学 ， 高分子化学与物理， 2011， 博士

【摘要】 具有复杂结构的高分子聚合物由于其优越的性能(如在溶液中丰富的自组装行为,微相形态结构及其纳米技术中的应用等),而引起了大家的广泛关注。因此,高分子聚合物的分子设计成为了高分子化学领域中一项极其重要的工作。近年来,由于活性/“可控”聚合技术,"Click" Chemistry偶合技术等的快速发展,为聚合物的合成提供了各种新颖的思路。特别是不同聚合反应机理和偶合技术的联合应用,更是为人们设计具有复杂结构聚合物提供了极大的便利。本文研究的氮氧自由基偶合反应,是一种新型而高效的偶合反应,它可以广泛地应用于复杂结构聚合物的合成与材料的表面修饰。这种偶合反应基于原子转移自由基聚合(ATRP)或者单电子转移自由基活性聚合(SET-LRP)的机理,在金属铜盐和配体的作用下,使聚合物末端的溴基团离去,形成“活性”自由基,然后通过另外一种聚合物末端的氮氧稳定自由基(一种自由基捕捉剂)将其捕捉,形成稳定的烷氧基胺键,完成聚合物之间偶合。根据碳自由基生成机理的不同,氮氧自由基偶合反应可分为原子转移氮氧自由基偶合反应(ATNRC)和单电子转移氮氧自由基偶合反应(SETNRC)。本课题对于氮氧自由基偶合反应的机理以及反应条件进行了详细的讨论,并将这种偶合反应与活性阴离子聚合、原子转移自由基聚合(ATRP)、“活性”开环聚合(ROP), "Click" Chemistry偶合技术联用,制备各种不同结构的嵌段聚合物。我们的主要工作以及结果如下：1.探寻反应温度、反应体系以及参与反应的溴基团结构对于反应的影响。采用ATRP技术,引发苯乙烯(St)、丙烯酸叔丁酯(tBA)、甲基丙烯酸甲酯(MMA)聚合,得到了带有不同结构溴基团的聚苯乙烯(PS-Br)、聚丙烯酸叔丁酯(PtBA-Br)和聚甲基丙烯酸甲酯(PMMA-Br)。同时,利用开环聚合(ROP),以4-羟基-2,2,6,6-四甲基哌啶氧自由基(4-Hydroxyl-2,2,6,6-tetramethylpiperidyl-1-oxyl, HTEMPO)为引发剂,引发ε-己内酯(ε-CL)聚合,得到末端带有TEMPO基团的聚ε-己内酯(PCL-TEMPO)。将PS-Br、PtBA-Br和PMMA-Br分别与PCL-TEMPO混合,在三个不同的反应体系中：(1) Cu0/PMDETA; (2) CuBr/PMDETA; (3) Cu0/CuBr/PMDETA,反应温度从室温(25℃)到90℃之间,观测反应温度、反应体系以及参与反应的溴基团结构的变化,对于偶合效率的影响,探寻适宜的偶合反应体系、反应温度以及所适用的溴基团结构。研究结果显示：在反应体系Cu0/PMDETA以及CuBr/PMDETA中,随着温度的升高,偶合效率下降了；在反应体系Cu0/CuBr/PMDETA中,在温度范围25～75℃之间,PtBA-Br的偶合效率都高于85%；在温度范围25～90℃之间,PS-Br的偶合效率皆高于90%；PMMA-Br只有在25℃下的偶合效率高于90%。2.联合应用原子转移氮氧自由基偶合(ATNRC)反应与“Click" Chemistry偶合技术,一步法合成了ABC型三嵌段聚合物PtBA-b-PS-b-PEO和PtBA-b-PS-b-PCL.首先,通过酯化反应,合成了两端分别带有炔丙基和溴基团小分子引发剂2-溴异丁酸丙炔酯(Propargyl 2-Bromoisobutyrate, PgBiB),然后以PgBiB为引发剂,采用ATRP技术引发苯乙烯(St)聚合,得到两端分别带有炔丙基和溴基团的聚苯乙烯(Alkyne-PS-Br)。接着,使用ATRP方法得到结构明确的末端带有溴基团的聚丙烯酸叔丁酯(PtBA-Br),利用端基叠氮化,得到末端带有叠氮基团的聚丙烯酸叔丁酯(PtBA-N3)。同时,利用开环聚合(ROP),以4-羟基-2,2,6,6-四甲基哌啶氧自由基(4-Hydroxyl-2,2,6,6-tetramethylpiperidyl-1-oxyl, HTEMPO)为引发剂,引发环氧乙烷(EO)和s-己内酯(ε-CL)聚合,得到末端带有TEMPO基团的聚环氧乙烷(PEO-TEMPO)和聚ε-己内酯(PCL-TEMPO).最后,将Alkyne-PS-Br, PtBA-N3以及PEO/PCL-TEMPO混合,在CuBr/PMDETA存在的条件下加热,炔基与叠氮基团发生"Click" Chemistry,溴基团与TEMPO基团之间发生ATNRC反应,一步法合成了两亲性ABC三嵌段聚合物PtBA-b-PS-b-PEO以及PtBA-b-PS-b-PCL。用1H NMR、GPC、FT-IR和DSC等手段对中间产物和目标产物进行了详细地表征。3.联合应用阴离子聚合,ATRP以及单电子转移氮氧偶合(SETNRC)反应,制备两亲性的ABC型三嵌段共聚物PI-b-PS-b-PEO、PI-b-PtBA-b-PEO以及PI-b-PAA-b-PEO。通过活性阴离子方法聚合异戊二烯,然后用EO作为小分子“盖帽”试剂进行封端反应,得到末端带有羟基的聚异戊二烯(PI-OH),通过2-溴异丁酰溴与羟基的酯化反应,得到末端带有溴基团的聚异戊二烯(PI-Br).以PI-Br为大分子引发剂,利用ATRP方法引发单体St以及tBA聚合,然后与PEO-TEMPO在室温下,以THF为溶剂,进行SETNRC反应。同时,研究了反应时间以及聚合物链长对于偶合效率的影响。结果显示：SETNRC反应在Cu0/Me6TREN体系中具有很高的反应速率,在2小时内达到91.6%；随着参与反应的聚合物链长的增长,偶合的效率快速下降。更多还原

【Abstract】 Block copolymers have attracted much attention for their potential excellent properties (e.g, their self-assembling behavior in solution, the morphologies of microdomain and applications in nano-field). Therefore, the synthesis of these copolymers with well-defined structure is an important work in polymer chemistry. Nowadays, with the development of controlling/"living" polymerization and "click" chemistry, it provides the mature and reliable technical support for synthesis of these copolymers. In particular, by means of the combination of different polymerizations with the coupling techniques, it is more effective to design and synthesize these copolymers with well-defined structure.Nitroxide radical coupling reaction was investigated and developed as a potential coupling technique in this field. The "living" radicals generated by atom transfer or single electron transfer mechanisms can be trapped by nitroxide stable radical (a radical capture agent) to form a new alkoxyamine bond. In this work, we investigated the mechanism and reaction condition of nitroxide radical coupling reaction. By means of combination of this coupling technology with other polymerizations (like living anionic polymerization, atom transfer radical polymerization and ring-opening polymerization) and coupling reaction (like click chemistry), a serial of block copolymers with different structures were synthesized. The essential results obtained are showed as follows:1. The effect of temperature, catalyst system and the structure of bromine connected groups on the nitroxide radical coupling (NRC) reaction was investigated. A series of polymers with different bromine connected groups as poly(tert-butyl acrylate) (PtBA-Br), polystyrene (PS-Br) and poly(methyl methacrylate) (PMMA-Br) are prepared by ATRP first, then the bromine-containing polymers were coupled with 2,2,6,6-tetramethylpiperidinyl-l-oxy-containing poly(ε-caprolactone) (PCL-TEMPO) in different catalyst systems as CuBr/PMDETA, Cu0/PMDETA and CuBr/Cu0/PMDETA in the temperature range from 90℃to 25℃. The result shows that the catalyst system of CuBr/Cu0/PMDETA is the best one for NRC reaction, in which the NRC reaction could be conducted in high efficiency in the wide temperature range from room temperature to high temperature. The efficiency of NRC reaction between PtBA-Br and PCL-TEMPO is more than 85% in the temperature range from 25～75℃, the efficiency between PS-Br and PCL-TEMPO is more than 90% from 25～90℃, and the efficiency between PMMA-Br and PCL-TEMPO is more than 90% only at the room temperature.2. A new strategy for one-pot synthesis of ABC type triblock copolymers via a combination of "click chemistry" and atom transfer nitroxide radical coupling (ATNRC) was suggested, and poly(tert-butyl acrylate)-block-polystyrene-block-poly (ethylene oxide) (PtBA-PS-PEO) and poly(tert-butyl acrylate)-block-polystyrene-block-poly(ε-caprolactone) (PtBA-PS-PCL) were successfully prepared by this method. The precursors with predetermined number average molecular weight and low polydispersity indices, such as PS with a-alkyne and co-bromine end groups, PtBA with azide end group, PEO and PCL with a 2,2,6,6-tetramethylpiperidine-l-oxyl end group, were directly prepared by living polymerization technique using the compounds with corresponding functional groups as initiators, and no further modification of the end groups were needed except P/BA-N3. The coupling reaction between precursors was carried out in the CuBr/PMDETA system with high efficiencies. All the copolymers and precursors were characterized by1H NMR、GPC、FT-IR and DSC in detail.3. A serial of ABC triblock copolymers as polyisoprene-block-polystyrene-block-poly(ethylene oxide) (PI-PS-PEO), polyisoprene-block-poly(tert-butyl acrylate)-block-poly(ethylene oxide) (PI-PtBA-PEO) and polyisoprene-block-poly(acrylic acide)-block-poly(ethylene oxide) (PI-PAA-PEO) were obtained by combination of anionic technique, atom transfer radical polymerization (ATRP) with single electron transfer nitroxide coupling (SETNRC) reaction. Anionic polymerization of isoprene followed by end-capping with ethylene oxide yielded hydroxyl terminated PI. After esterification, PI with Br end group was used as a macroinitiator to initiate the polymerization of St and tBA by ATRP, then trapped by 2,2,6,6-tetramethylpiperidine-1-oxyl group in poly(ethylene oxide) by single electron transfer nitroxide radical coupling (SETNRC) reaction rapidly with high efficiency in THF at room temperature. The effect of reaction time and polymer chain length on SETNRC reaction was discussed in detail. In the present of Cu0/Me6TREN, SETNRC between PI-PS-Br and PEO-TEMPO was carried out with the efficiency up to 91.6% in 2 hours. With the polymer chain length increasing, the efficiency decreased fleetly.更多还原