【作者】 伍广朋；

【导师】 吕小兵；

【作者基本信息】 大连理工大学 ， 应用化学， 2012， 博士

【摘要】 二氧化碳(CO2)问题日益受到各国的重视,关注焦点已经从单纯的捕集和填埋转向碳氧资源的综合利用,其中CO2作为碳源参与高聚物的构筑已经成为高分子学科的重要研究领域。其中由CO2和环氧烷烃共聚生成聚碳酸酯(CO2共聚物)这一绿色聚合反应最具潜力。尽管在前期研究工作的带动下,CO2共聚物的工业化已经具备一定基础,但却受制于材料性能、品种单一等问题,发展十分缓慢,主要原因在于CO2共聚物非晶且玻璃化转变温度较低,导致高温强度迅速变差等。基于上述瓶颈问题,本论文的研究工作致力于设计合成具有结晶能力的二氧化碳基高分子材料；同时拓展环氧烷烃底物范围,将现代医药和树脂工业中广泛应用的环氧苯乙烷(SO)和环氧氯丙烷(ECH)等含吸电子基团的环氧烷烃用于CO2共聚物构筑以制备功能化的二氧化碳基高分子材料。1设计合成了非对称手性四齿席夫碱钴配合物与氯化双(三苯基正膦基)亚铵(PPNCl)组成二元催化体系,用于CO2和环氧环己烷(CHO)的不对称交替共聚反应,100%选择性生成聚碳酸酯。该聚合产物中碳酸酯单元含量高于99%,呈现出完美的交替共聚结构。证明了手性环氧丙烷(PO)与CHO的竞争配位可有效促进CHO的对映选择性开环。在此基础上,利用手性的2-甲基四氢呋喃作为竞争配位手性源,得到了全同立构规整度为98%的聚碳酸环己烯酯(PCHC),为迄今报道的最高值。2研究了具有高立构规整度PCHC的结晶行为和结晶形态。广角X射线衍射表明单一光学纯度的PCHC在20=12.2,17.9,19.0和20.4°有强衍射峰出现,属于典型的半结晶性高分子材料,熔点(Tm)为216℃。结晶形态研究表明,单一光学纯度PCHC的球晶以逆时针方向生长,(R)-PCHC的球晶以顺时针方向生长。(S)-PCHC和(R)-PCHC通过等量共混,在20=8.6,17.9和21.5°出现新的强衍射峰,形成了立构复合结构,球晶为板条状的晶态形貌,并表现出了更强的抗热形变能力(Tm=230℃)。这是自1969年CO2和环氧烷烃的交替共聚反应被报道以来首次制备出的具有结晶性能的二氧化碳基高分子材料。3利用基于SalenCo(III)配合物的双组分催化剂,详细研究了含吸电子性基团环氧苯乙烷(SO)/C02的共聚反应和PO/CO2的共聚反应中催化活性、区域及立体选择性的不同。在此基础上,通过改进催化剂结构、优化反应条件,提出了高效SO/CO2聚合催化体系的设计原则,得到了高产物选择性、完全交替结构的聚碳酸苯乙烯酯。凝胶渗透色谱(GPC)结果表明SO/CO2的交替共聚呈现良好的活性聚合特征。合成了系列寡聚二元碳酸苯乙烯酯模式化合物,完成了聚碳酸苯乙烯酯的微结构(头头、头尾和尾尾结构单元)的碳核磁指认。以手性SO为反应底物,利用具有多手性因素的钴配合物得到了立构规整度达96%的聚碳酸苯乙烯酯。进一步拓宽催化体系的适用性,将官能团化的对氯苯乙烯环氧化物与C02进行立体选择性交替共聚反应,制备了具有氯官能团、光学活性的功能化C02共聚物。该聚合物的玻璃化转变温度(Tg)和热分解温度(T50)分别为92℃和310℃,具有较高的热稳定性。开展了对CO2、so和PO或CHO的三元调聚合研究。利用Fineman-Ross方程详细考察了不同反应单体的竞聚率,成功制备了碳酸苯乙烯酯和碳酸环己烯酯两种碳酸酯单元交替为主的三元共聚物。4考察环氧氯丙烷(ECH)与C02交替共聚反应的聚合特征。通过比较ECH/CO2与PO/CO2共聚反应在产物选择性、催化活性等方面的不同,优化出催化剂结构及反应条件,第一次得到了完全呈交替结构的ECH/CO2共聚物。动力学研究表明,ECH/CO2共聚反应中聚碳酸酯和环状碳酸酯之间较小的活化能差(45.4kJ/mol),是形成大量环状副产物的根本原因。以位阻性有机强碱7-甲基-1,5,7-三氮双环[4.4.0]癸-5-烯(MTBD)作为助催化剂,利用飞行时间质谱对聚合反应进行了原位跟踪监测,直接观察到了聚合反应的链引发及增长过程。在此基础上,结合反应过程中关键中间体的捕捉及单晶结构分析,提出了ECH/CO2交替共聚反应可能的机理。同时,研究了该单体与CO2的区域及立体选择性共聚合,并以手性的ECH为反应底物,利用席夫碱配体苯环3位上具有大位阻取代基的双功能催化剂,制备了立构规整度97%的ECH/CO2交替共聚物。广角X射线衍射及热分析结果表明高立构规整性的交替共聚物具有良好的结晶性能,聚合物的结晶温度为108℃。更多还原

【Abstract】 CO2emission has aroused great attention in the world, and the focus of this issue has switched from simple CO2capture and landfill to its comprehensive utilization. CO2as starting material for building macromolecular polymers has become an important research field of polymer science. The coupling of epoxide and CO2to produce the biodegradable polycarbonate (CO2-based copolymer) has been regarded as the most promising green polymerization process. Although the commercialization of CO2-based copolymer has already obtained certain progress in recent years, the further development of this green technology is suffering from material performance as well as product type etc. One of the main problems is that all these previously reported CO2copolymers are amorphous and have low glass transition temperatures, which make the strength sharply decrease at enhanced temperatures. In terms of the above bottle-neck problems, in this dissertation, we made an effort to synthesize crystalline CO2-based copolymer. Moreover, we tried to produce functional CO2-based polymers from epoxides with electro-withdrawing groups, such as styrene oxide (SO) and epichlorohydrin (ECH) used in resin industry.1. Binary catalyst systems consisted of unsymmetric enantiopure salenCo(III) complexes and bis(triphenylphosphine)iminium chloride (PPNCl) were developed for the asymmetric alternating copolymerization of CO2and cyclohexene oxide, affording poly(cyclohexene carbonate)s with100%selectivity. The resultant copolymers have more than99%carbonate linkages, indicating the perfect alternating nature. It was found that the competition coordination of (S)-propylene oxide significantly improved the enantioselectivity regarding (S,S)-salenCo(Ⅲ) catalyst systems. With (S)-2-methyltetrahydrofuran as a chiral induction agent, the stereoregularity of the resultant poly(cyclohexene carbonate)(PCHC) is up to98%, the highest record in this asymmetric polymerization catalysis.2. The crystallization behavior of highly stereoregualr PCHC was studied by wide angle X-ray diffraction (WAXD) and atomic force microscopy (AFM). According to the strong diffraction peaks2θ at12.2,17.9,19.0,20.4°. the highly stereoregular PCHC is a typical semi-crystalline thermoplastic, possessing a high Tm of216℃. Crystallization shape observations show that the spherulitic morphology of (R)-PCHC grows in a clockwise spiral from a centre, while that of (S)-PCHC is counterclockwise spiral. Also, it is demonstrated the formation of stereocomplex from the blend of equivalent (R)-PCHC and (S)-PCHC with new strong diffraction peaks2θ=8.6,17.9,21.5°. Unlike its parent polymers, the PCHC stereocomplex presents lath-like dendritic crystal and better thermal deformation ability (Tm= 230℃). This is the first example of crystalline CO2-based polymer since the CO2/epoxide copolymeriztation was first reported in1969.3. Detailed study on the difference in reactivity between styrene oxide (SO) versus PO during the copolymerization with CO2has been conducted, with a focus on the catalytic reactivity, regio-and stereo-selectivity. Furthermore, the alternating copolymerization of CO2and SO to afford the corresponding polycarbonate with more than99%carbonate linkages was achieved with the use of the optimized catalyst systems. A living polymerization process was observed in the CO2/SO copolymrization on the basis of gel permeation chromatography (GPC). In order to assign carbonate signals of poly(styrene carbonate) microstructure, various model compounds to simulate three carbonate linkages of this CO2copolymer, including head-to-head, head-to-tail and tail-to-tail linkages, were synthesized. The highest regioselective ring-opening with96%configuration retention was obtained. Additionally, the reactivity of SO derivatives in the copolymerization with CO2was also tested. The CO2copolymer from4-cholro styrene oxide exhibits excellent thermal stability with a thermolysis temperature up to310℃and a high glass-transition temperature of92℃. The Fineman-Ross plots were performed to determining the monomer reactivity ratios in the CO2/SO/PO and CO2/SO/CHO terpolymerizations. The reactivity ratios indicate that it is favorable to alternating structure of the two different carbonates units, rather than homo-carbonate linkages in the CO2/SO/CHO terpolymers.4. On the basis of the copolymerization of SO/CO2, a systematic comparation of the difference in reactivity between epichlorohydrin (ECH) versus PO during the copolymerization with CO2has been well conducted. The alternating copolymerization of CO2and ECH to afford the corresponding polycarbonate with more than99%carbonate linkages was first achieved with the use of the optimized catalyst systems. Comparative kinetic measurements were performed as a function of reaction temperature to assess the activation barrier for production of cyclic carbonates and polycarbonates for the ECH/CO2and PO/CO2coupling systems. The relative small energy difference (45.4kJ/mol) for the ECH/CO2process accounts for the large quantity of cyclic carbonate produced compared with PO/CO2process. Electrospray ionization mass spectrometry (ESI-MS) in combination with single crystal structures of key intermediates can provide a straightforward approach to insight into the details of the copolymerization of CO2and ECH, regarding sterically hindered organic base7-methyl-1.5,7-triazabicyclo[4.4.0]dec-5-ene (MTBD). A complex with the bulky groups on the3position has been developed for the highly selective copolymerization of CO2/ECH. The highest regioselective ring-opening with97%configuration retention at methine carbon was obtained. Wide angle X-ray diffraction and differencial scanning calorimeter show the stereospecific polymers exhibit good crystallizability with high melting boint at108℃.更多还原