席夫碱铝、锌配合物催化丙交酯和ε-己内酯开环聚合

发布时间：2018-04-16 15:23

本文选题：聚乳酸 + 聚ε-己内酯　；参考：《吉林大学》2017年硕士论文

【摘要】：聚乳酸(PLA)和聚ε-己内酯(PCL)作为领先的生物可降解合成聚酯,已经引起人们越来越多的关注。较比于直接聚合,开环聚合(ROP)丙交酯(LA)和ε-己内酯(ε-CL)单体能够获得高分子量的PLA和PCL产物。对于LA的聚合,异构体的作用对所得PLA材料的物理、机械、流变和降解性能至关重要。金属配合物能够良好地控制PLA结构和性能是生产PLA最有效的方法,包括分子量、组成、微结构和单体结合等方面,尤其是立体选择性ROP,所得PLA的立构规整度,显著影响其物理和化学性能。基于我们前期的工作,第一部分我们以三种双金属中心席夫碱铝配合物催化LA和ε-CL开环共聚,制备了一系列不同单体比例的共聚物。利用核磁(NMR)结果分析测定了共聚物中LA与ε-CL结构单元的比例及平均链段长度。通过对左旋丙交酯(L-LA)和外消旋丙交酯(rac-LA)分别与ε-CL开环共聚反应的动力学性能进行对比研究,发现该催化体系中LA的聚合速率快于ε-CL,而L-LA的聚合速率又略快于rac-LA。由此可以推知:所得共聚物为微观组成渐变的梯度共聚物。利用DSC对所得共聚物进行了热力学性能表征,发现随着两种结构单元比例的变化,共聚物的玻璃化转变温度(T_g)呈现规律性变化。鉴于金属配合物很难从聚合产物中分离干净从而限制材料的应用,人们更愿意使用无毒金属(锌)配合物催化环酯开环聚合。第二部分我们基于烯醇式配位结构,成功设计、合成和表征了一系列烯醇式单金属中心锌配合物,作催发剂催化LA、ε-CL开环聚合。研究发现烯醇式锌配合物在聚合LA过程中表现出较高活性,催化剂苯环取代基的存在和配位胺桥的增长,易于单体配位插入的关系,能够显著提高催化剂的活性,配合物4a表现出最高的催化活性。聚合结果还发现催化体系异丙醇加入与否,对催化聚合反应并无影响,聚合物端机和NMR结果分析表明加入异丙醇并不参与配位。
[Abstract]:Polylactic acid (PLA) and poly (蔚 -caprolactone) (PCL) have attracted more and more attention as a leading biodegradable synthetic polyester.Compared with direct polymerization, ring-opening polymerization (ROP) lactide (LA) and 蔚 -caprolactone (蔚 -CL) monomers can obtain high molecular weight PLA and PCL products.For the polymerization of LA, the action of isomers is very important to the physical, mechanical, rheological and degradation properties of the obtained PLA materials.The structure and properties of PLA can be well controlled by metal complexes, which include molecular weight, composition, microstructure and monomers, especially stereoselective PLA.The physical and chemical properties are significantly affected.Based on our previous work, in the first part, a series of copolymers with different monomer ratios were prepared by the ring-opening copolymerization of LA and 蔚 -CL catalyzed by three kinds of bimetallic center Schiff base aluminum complexes.The ratio of LA to 蔚 -CL units and the average length of chain segments in the copolymers were determined by NMR.The kinetic properties of the ring-opening copolymerization of L-LLA and rac-lactide with 蔚 -CL were compared. It was found that the polymerization rate of LA was faster than that of 蔚 -CLand and the polymerization rate of L-LA was a little faster than that of rac-LA.It can be inferred that the obtained copolymer is a gradient copolymer with gradual microstructure.The thermodynamic properties of the copolymers were characterized by DSC. It was found that the glass transition temperature (TG) of the copolymers changed regularly with the change of the ratio of two structural units.In view of the fact that metal complexes are difficult to separate from polymeric products and thus limit the application of materials, nontoxic metal (zinc) complexes are preferred to catalyze the ring-opening polymerization of cycloesters.In the second part, based on the enol coordination structure, a series of enol monometallic zinc complexes were successfully designed, synthesized and characterized, which were used as catalysts to catalyze the ring-opening polymerization of LA-CL.It was found that the enol zinc complex exhibited high activity during the polymerization of LA. The presence of benzene ring substituents and the increase of the coordination amine bridge of the catalyst could improve the activity of the catalyst.Complex 4a showed the highest catalytic activity.The polymerization results also showed that the addition of isopropanol had no effect on the catalytic polymerization. The results of polymer terminal and NMR showed that the addition of isopropanol did not participate in the coordination.
【学位授予单位】：吉林大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：O643.3;O631.5

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