【作者】 张红霞；

【导师】 李杨；

【作者基本信息】 大连理工大学 ， 高分子材料， 2009， 博士

【摘要】 高支化聚合物作为树枝形聚合物家族中继树形和超支化聚合物之后的新成员,由于其兼具有树形聚合物的迭代增长和超支化聚合物的支链无规分布的特点,并拥有以聚合物链为接枝单元,反应步骤少可合成高分子量且窄分子量分布(MWD<1.50)的高支化聚合物的优势,日益引起人们的普遍关注。活性阴离子聚合是实现聚合物分子结构设计最为精确和有效的方法之一,但由于其对杂质极其敏感,用来合成高分子量聚合物的难度较大。将活性阴离子聚合和偶联反应技术相结合来合成结构可控的高分子量的高支化聚合物是一个重要的研究方向。目前通过偶联法来合成的高支化聚合物一般是以线形聚合物为基质的,其分子拓扑结构比较单一。本文采用活性阴离子聚合和偶联反应技术合成了星形液体聚丁二烯,通过原位过氧甲酸法环氧化反应并精制得环氧化星形液体聚丁二烯偶联剂,以此新型环氧化物偶联剂进行偶联反应成功制备了一系列丁二烯/异戊二烯/苯乙烯星形梳状聚合物,并已形成专利技术;以环氧化星形液体聚丁二烯为偶联剂,制备了新型的星形梳状丁二烯/苯乙烯嵌段共聚物,其冲击性能十分优异,并已形成专利技术。本文始终贯穿高分子设计思想,以正丁基锂为引发剂、环己烷为溶剂、四氢呋喃为极性添加剂、环氧化物为偶联剂,立足于三种大宗单体一丁二烯、异戊二烯、苯乙烯,采用环氧化反应-偶联反应迭代增长技术合成了线形梳状高支化聚丁二烯、星形梳状高支化聚丁二烯和星形梳状高支化聚异戊二烯,并采用环烷酸镍/三异丁基铝催化体系对G0-G4代星形梳状高支化聚丁二烯进行加氢反应得到G0-G4代星形梳状高支化聚乙烯,同时对高支化聚合物的分子参数、支化参数和热性能等进行了较为深入的研究。纵观全文,主要结论如下:采用活性阴离子聚合技术设计合成线形和星形液体聚丁二烯,通过原位过氧甲酸法环氧化反应制备环氧化线形和星形液体聚丁二烯,精制后得可用于阴离子聚合体系的不含卤原子的环氧化线形和星形液体聚丁二烯偶联剂。以星形聚丁二烯为基质,以环氧化聚丁二烯为偶联剂,采用环氧化反应-偶联反应的迭代增长技术首次合成拓扑结构新颖的G0-G4代星形梳状高支化聚丁二烯:分级后G0-G4代星形梳状高支化聚丁二烯均具有对称的单峰且为窄分布(MWD<1.23),其分子量和支化度随着代数增加而呈几何级数的增长;支化因子随着代数的增加,逐渐变小;星形梳状高支化聚丁二烯的分子拓扑是密实的球形结构。G4代星形梳状高支化聚丁二烯的分子量分布仅为1.17,重均分子量(M_w)高达1.4×10~7,其支化度(f_w)高达3700,支化因子(g’)仅为0.0040。采用环烷酸镍/三异丁基铝催化体系对分级后的G0-G4代星形梳状高支化聚丁二烯氢化反应,首次制备了高支化的G0-G4代星形梳状聚乙烯,其加氢度均大于99.0%,并具有一定结晶性和极性,是一类良好的模型聚乙烯。G4代星形梳状高支化聚丁二烯为G0-G4代星形梳状高支化聚丁二烯中分子量最高且支化程度也最高的星形梳状高支化聚丁二烯(M_w=1.8×10~7,f_w=6790),其加氢难度也最大,氢化G4代星形梳状高支化聚丁二烯的加氢度也高达99.5%;高度支化的氢化G4代星形梳状聚丁二烯的熔点和结晶温度均较低,且其结晶度仅为22.2%,但其耐热性比加氢前有了显著提高。以星形聚异戊二烯为基质,以环氧化聚异戊二烯为偶联剂,采用环氧化反应-偶联反应的迭代增长技术,首次合成了拓扑结构新颖的G0-G4代星形梳状高支化聚异戊二烯:随着代数的增加,其分子量和支化度呈几何级数的增长,支化因子随着代数的增加,逐渐变小;星形梳状高支化聚异戊二烯的分子拓扑是疏松的球形结构。G4代星形梳状高支化聚异戊二烯的重均分子量高达3.6×10~6,其支化度为765,而支化因子仅为0.0091。以环氧化星形液体聚丁二烯为偶联剂合成了结构新颖的星形梳状丁苯嵌段共聚物,其缺口冲击强度高达216J/m,且为冲击不断的材料。更多还原

【Abstract】 The third class dendritic polymers, the dendrigraft polymers, combine features of dendrimers and hyperbranched polymers. The syntheses of dendrigraft polymers follow a generation-based growth scheme similar to dendrimers. Since the coupling reaction is a random process, the branched structure of dendrigraft polymers is similar to that of hyperbranched polymers. Utilization of polymeric chains as building blocks leads to a very rapid increase in molecular weight per generation, and the branched polymers with high molecular weight and narrow molecular weight distribution (MWD<1.50) can be produced in a few steps. As such, the dendrigraft polymers are increasingly a focus of widespread interests. Anionic polymerization is one of the most accurate and effective methods for the design of polymer architecture, though the synthesis of high molecular weight polymers is severely challenging due to its extremely sensitive to system cleanliness. The combination of anionic polymerization and coupling reaction for preparation of a high molecular weight and highly branched polymers with a controlled architecture is an important research direction. Recently, the dendrigraft polymers have been synthesized by grafting-onto method with a linear polymer chain serving as ’core’ for the molecules, and its molecular topology is relatively simple.In this paper, star liquid polybutadienes were synthesized by the living anionic polymerization and coupling reaction, and then epoxidized by in situ peroxyformic acid. The epoxidized star liquid polybutadienes were refined until water and oxygen content below 10ppm to use as coupling agent for anionic polymerization system. A series of butadiene/isoprene/styrene star-comb homopolymers were successfully synthesized with the epoxidized star liquid polybutadiene as coupling agent, and the method has applied a Chinese patent; the star-comb butadiene/styrene block copolymers (SC-SBC) were prepared with the epoxidized star liquid polybutadiene as coupling agent, the impact performances of SC-SBCs are very excellent, and the method has applied a Chinese patent. Based on the philosophy of macromolecular design throughout the thesis, the author fully utilized the monomers of butadiene, isoprene, and styrene produced in bulk to synthesize a series of novel dendrigraft polymers with n-butyllithium as initiator, cyclohexane as solvent, THF as polar additives, epoxidized polymer as coupling agent. Following were the typical dendrigraft polymers prepared in this work, including the linear-comb dendrigraft polybutadiene, the star-comb dendrigraft polybutadiene, and the star-comb dendrigraft polyisoprene. In addition, the G0-G4 star-comb dendrigraft polybutadienes were hydrogenated by nickel naphthenate/3-isobutyl aluminum catalyst system to obtain G0-G4 star-comb dendrigraft polyethylenes. Furthermore, the molecular parameters、branching factors and thermal properties of the novel dendrigraft polymers mentioned above were thoroughly investigated.From the summary of the full thesis, it came to the main conclusions that:The linear and star liquid polybutadienes were synthesized by anionic polymerization and subsequent epoxidized by in situ peroxyformic acid method. Then the epoxidized liquid polybutadienes were refined and used as coupling agent for anionic polymerization system.A series of G0-G4 star-comb dendrigraft polybutadienes were successfully synthesized by cycles of epoxidation and coupling reaction with epoxidized polybutadiene as coupling agent and star polybutadiene as ’core’. The star-comb dendrigraft polybutadienes have narrow molecular weight distributions (MWD<1.23) consistent with a uniform molecular size and display geometric increases in molecular weight and branching functionality for successive generations. The branching factors decrease quickly as the increase of generation number. The molecular topology of the star-comb dendrigraft polybutadiene has a dense spherical structure. G4 star-comb dendrigraft polybutadiene has narrow MWD as low as 1.17, high molecular weight up to 1.4×10~7, branching functionality up to 3700, and branching factor as low as 0.0040.A series of G0-G4 star-comb dendrigraft polybutadienes were converted into the corresponding G0-G4 star-comb dendrigraft polyethylenes through the hydrogenation of polybutadienes. Catalytic hydrogenation was carried out with nickel naphthenate/ triisobutylaluminium system. The hydrogenation degrees of G0-G4 hydrogenated star-comb dendrigraft polybutadienes are as high as 99.0%. The star-comb dendrigraft polyethylenes exhibit certain degree of crystallinity and demonstrate certain degree of polarity, and are a class of good model polyethylene. G4 star-comb dendrigraft polybutadiene (M_w=1.8×10~7, f_w=6790), the highest molecular weight and most highly branched among G0-G4 star-comb dendrigraft polybutadienes, also has the bigger difficulty during hydrogenation. The hydrogenation degree of G4 hydrogenated star-comb dendrigraft polybutadiene is up to 99.5% and its degree of crystallinity is only 22.2%. Due to highly branched structure, G4 star-comb dendrigraft polyethylene has low melting temperature and crystallization temperature. Compared to G4 star-comb dendrigraft polybutadiene, the thermal stablity of G4 star-comb dendrigraft polyethylene has increased.A series of G0-G4 star-ccmb dendrigraft polyisoprenes were successfully synthesized by cycles of epoxidation and coupling reaction with epoxidized polyisoprene as coupling agent and star polyisoprene as ’core’. The star-comb dendrigraft polyisoprenes display geometric increases in molecular weight and branching functionality for successive generations. The branching factors decrease as the increase of generation number. The molecular topology of the star-comb dendrigraft polyisoprenes has a loose spherical structure. G4 star-comb dendrigraft polyisoprene has narrow MWD as low as 1.17, high molecular weight up to 3.6×10~6, branching functionality up to 765, and branching factor as low as 0.0091.The star-comb styrene/butadiene block copolymer was synthesized by anionic polymerization and coupling reaction with epoxidized star liquid polybutadiene as coupling agent. The notched izod impact strength of the star-comb butadiene/styrene block copolymer reaches as high as to 216J/m. The instrumented impact curve shows that the material is no fracture in 4ms.更多还原