希夫碱—后过渡金属（d）/混金属（d-f）催化剂及开环聚合丙交酯的研究

【作者】 靳文娟；

【导师】 吕兴强；

【作者基本信息】 西北大学 ， 应用化学， 2010， 硕士

【摘要】 聚乳酸,不仅具有较好的强度、通透性、柔韧性、化学惰性、可降解性和易加工等特点,而且具有良好的生物相容性,在医用高分子材料、医药等领域有诱人的应用前景,而体现其性能的系列指标如聚合物分子量大小、分子量分布及聚合物微结构等所需要的催化剂的分子设计仍充满挑战。本论文通过酐胺缩合反应,设计合成了系列非手性及手性的希夫碱化合物,并通过其与后过渡金属离子(如Cu2+、Ni2+等)和稀土金属离子(如Ce3+、Nd3+、Sm3+、Eu3+、Tb3+、Ho3+、Tm3+等)进一步配位反应,合成得到四个系列各具特色的催化剂：非手性单活性中心催化剂、手性单活性中心催化剂、非手性双活性中心催化剂和手性双活性中心催化剂,并通过元素分析(EA)、红外光谱(IR)、核磁共振氢谱(1H NMR)、紫外可见光吸收光谱(UV-Visible Aborsorption)、单晶衍射(XRD)等手段进行了结构表征；利用熔融缩聚法,系统考察了催化剂对L-丙交酯(L-Lactide)、D,L-丙交酯(D,L-Lactide)等的开环聚合行为,聚合产物用凝胶渗透色谱(GPC)测定其分子量大小和分子量分布,并用红外光谱(FT-IR)、热重分析(TGA)、核磁共振光谱(1H NMR及13C NMR)等手段对聚合物的微结构进行了表征,并尝试通过分析催化剂的结构特点和其聚合产物的性质之间的关系,探讨通过催化剂的结构调整其催化活性进而得到相应分子量区间的聚合物的可控性。首先,合成了10个不同结构的非手性单活性中心催化剂,并考察了其对丙交酯的开环聚合行为：系统研究了催化剂的共轭效应、推拉电子效应、位阻效应及活性中心类型等结构特点与其聚合产物的性质之间的对应关系。第二,通过引入手性,合成了4个手性单活性中心催化剂,考察了其对外消旋丙交酯(D，L-LA)和旋光纯丙交酯(L-LA)的开环聚合行为,系统研究了催化剂的共轭效应、手性效应、位阻效应及活性中心类型等结构特点与其聚合产物的性质之间的对应关系。第三,以后过渡金属非手性配合物为前驱体,引入第二个活性中心(不同离子半径的稀土金属离子),合成了8个不同结构的双活性中心非手性催化剂,考察了其对L-LA的开环聚合行为,对比研究了单、双活性中心及不同离子半径的活性中心对催化剂的活性大小的影响,探讨了催化剂结构特点与其聚合产物的性质之间的对应关系。第四,在非手性双金属配合物的基础上引入手性,合成了7个手性双金属催化剂,对比研究了催化剂手性的引入对L-LA的开环聚合行为的影响及活性中心的不同离子半径对催化剂的活性大小的影响。另外,从聚合工艺的角度,对四种具有代表性且催化活性较高的催化剂(B1、B2、C1、C4)做了单因素和正交试验,从中寻找到了最佳工艺条件,优化了催化聚合的工艺。更多还原

【Abstract】 Polylactide, with the characteristic properties of high mechanical strength, flexibility, chemical inertness, degradability and easy processability besides the biocompatibility, could be well used in the fields of biomedical polymer materials and medicines, while the molecular design of needed polymerization catalysts, which endows the properties for the obtained polymers from the sizes of molucular weights, the distributions of molecular weights and the microstuctures, has continuously been a big challenge to the polymerization.This thesis designed and synthetised a series of achiral or chiral Salen type Schiff-base compounds from the condensation reactions from aldehydes and diamines, and from which by the further coordination reaction with late transition metal ions (Cu2+or Ni2+) and/or rare earth metal ions (Ce3+, Nd3+. Sm3+, Eu3+, Tb3+, Ho3+ or Tm3+) obtained four series of distinctive catalysts:achiral single-site catalysts、chiral single-site catalysts、achiral double-sites catalysts and chiral double-sites catalysts. The structures of all the catalysts were characterized by the infrared spectra (FT-IR), the nuclear magnetic resonance spectra (NMR), the ultraviolet visible absorption spectra (UV-Visible absorption) and the X-ray diffraction analyses (XRD). From the bulk solvent-free melt ring-opening polymerization of L-lactide or racemic D,L-lactide catalyzed by the above mentioned catalysts, the resulting polymers were characterized by the FT-IR, NMR (’H NMR or 13C NMR) or TGA (thermogravimetric analysis), and their molecular weights (Mw or Mn) and molecular weight distributions (PDI) were determined by gel permeation chromatography (GPC) with polystyrene as standard. The correlation of the molecular structures versus the catalytic activities showed that the designed catalysts could as expected efficiently catalyze the ring-opening polymerization of lactide, with moderate molecular weights and narrow molecular weight distributions in the controllable mode.Firstly, ten achiral single-site catalysts from the late transition metal (Cu2+ or Ni2+) complexes based on different Salen-type Schiff-base ligands were obtained, and their ring-opening polymerization behaviors of L-lactide or racemic D,L-lactide were checked in detail. The catalytic results showed that structural characters of the catalysts, such as the conjugation effect, the push-pull electronic effect, the steric effect or the type of active centers, were the important and influential factors contributing to the catalytic activities.Secondly, four chiral singer-site catalyst from the late transition metal (Cu2+ or Ni2+) complexes based on different chiral Salen-type Schiff-base ligands were obtained, and their ring-opening polymerization behaviors of L-lactide or racemic D,L-lactide were studied. The results showed that efficient and controllable ring-opening polymerizations of lactide were gotten.Thirdly, with the the late trasition metal achiral complex as the precursor, eight double-sites catalysts were obtained from the involvement of rare earth ions (Ce3+, Nd3+, Sm3+, Eu3+, Tb3+, Ho3+ or Tm3+), and their molecular structures were characterized by the EA (element analyses), FT-IR and XRD. The behaviors of their catalytic polymerization on L-lactide showed that the presence of the second active center was apt to the improvement of the efficiency and the controllability from the ring-opening polymerization of L-lactide.Fourthly, from the reaction of the designed late trasition metal chiral complex with the Ln(NO3)3 (Ln3+= Ce3+, Nd3+, Sm3+, Eu3+, Tb3+, Ho3+ or Tm3+), seven double-sites chiral catalysts were obtained and used for the ring-opening polymerizations of L-lactide. The results showed that the polymerization difference was attributed to the different types of selected rare earth ions.In addition, from the viewpoint of the polymerization process, the series of factors, such as temperature, the ratio of monomer versus catalyst or reaction time were studied, respectively, and the optimized polymerization condition was founded on the design of the orthogonal test for the selected four catalysts (B1、B2、C1、C4).更多还原