【作者】 张治国；

【导师】 吕德伟； 陈志荣；

【作者基本信息】 浙江大学 ， 化学工程与技术， 2005， 博士

【摘要】 随着科学技术的飞速发展,环氧乙烷和环氧丙烷的开环聚合产物已经形成了规模庞大的聚醚系列产品群。本文选取环氧乙烷和环氧丙烷的开环聚合为研究对象,运用多种研究手段从开环聚合反应机理、开环聚合反应动力学行为和开环聚合产物的构效关系等方面对烷氧基化开环聚合过程进行了较为全面的研究,以进一步推动和加强我国环氧乙烷和环氧丙烷的开环聚合研究工作。 本文首先通过量子化学计算方法对烷氧基化开环聚合反应机理进行理论研究。运用前线轨道理论从微观电子结构层次上对环氧烷的各种聚合反应机理进行了分析,探讨了烷氧基化开环聚合反应阴离子和阳离子聚合机理的合理性。进而采用量子化学B3LYP/6-31G+(d)方法、HF/6-31G+(d)方法从理论上研究了烷氧基化开环聚合反应的途径,给出各基元反应的活化能。结果表明,环氧乙烷在碱催化条件下的聚合机理是由伯醇型氧负离子引发的S_N2型反应机理;环氧乙烷的阳离子聚合机理是由叔氧鎓离子参与的S_N2型反应机理;而环氧丙烷在碱催化条件下的聚合机理是由仲醇型氧负离子引发的S_N2型反应机理;向环氧丙烷发生的链转移反应主要通过从环氧丙烷中的甲基中失去氢原子的重排反应历程来进行。以上计算结果很好地阐明了实验事实。 在理论研究的基础上建立了相应的烷氧基化开环聚合反应模型并进一步研究了环氧乙烷和环氧丙烷的聚合反应动力学行为,包括烷氧基化聚合反应的微观动力学行为,以及在循环喷雾式聚合反应器中进行的烷氧基化反应的宏观动力学行为。本文首次在全面考虑了链引发过程细节以及链转移反应和质子交换反应后推导得到烷氧基化阴离子聚合产物的理论分布,常用的Flory分布和W-N-G分布都只是该分布在某些情形下的简化形式。对目前国际上广泛使用的Press循环喷雾式聚合反应器在烷氧基化反应中的传质特性与动力学规律进行了详细的考察,给出了环氧乙烷和环氧丙烷共聚合反应机理模型,建立了共聚合反应动力学模型。通过对实验数据的数值拟合求取了动力学模型中的各个反应速率常数和质子交换平衡常数,进而得到了各基元反应的活化能。 在动力学研究结果的基础上,本文建立了相应的Monte Carlo模拟模型,验更多还原

【Abstract】 With the rapid development of science and technology, there has been a growing interest in the polyethers (primarily homopolymers and copolymers of ethylene oxide and propylene oxide), which have the properties of excellent surface activity, flexibleness of HLB and low toxicity to form a wide variety of polyether series. In this dissertation, the ring-opening polymerization mechanism of ethylene oxide and propylene oxide, the polymerization kinetics and the properties of polyethers are studied using various methods to develop high quality polymerization products and improve the alkoxylation process.Firstly, quantum chemical methods are employed to investigate the mechanism of ring-opening polymerization of ethylene oxide and propylene oxide. By analysis of their frontier orbitals, the reasonability of the cationic and anionic polymerization mechanism of ethylene oxide and propylene oxide is confirmed theoretically. Furthermore, the reaction path of alkoxylation process and the activation energies of respective elementary reactions are studied by B3LYP/6-31G+(d) and HF/6-31G+(d) methods, the results show that the anionic ring-opening polymerization of ethylene oxide proceeds by nucleophilic attack of the primary alcohol propagating anion on monomer, the cationic ring-opening polymerization of ethylene oxide proceeds by nucleophilic attack of monomer on the tertiary oxonium ion and the anionic ring-opening polymerization of propylene oxide proceeds by nucleophilic attack of the secondary alcohol propagating anion on monomer. Calculation results could explain the experimental facts satisfactorily.The polymerization kinetics of ethylene oxide and propylene oxide is studied from the microscopic and macroscopic aspects. The theoretical product distribution is deduced with full consideration of the initiation, propagation, chain transfer and proton exchange reactions, and the most widely used theoretical distribution models, Flory and W-N-G, are the reduction of this distribution. The mass transfer and kineticsin alkoxylation spray tower loop reactors are studied, whereafter a copolymerization kinetic model of allyl polyether in alkoxylation spray tower loop reactors is established based on the copolymerization mechanism. The kinetic and equilibrium constants of the described model are determined by regression analysis of the experimental data.The Monte Carlo simulation is employed to validate the copolymerization of ethylene oxide and propylene oxide following the first order Markov model and the sequence distributions of monomer units in copolymers are illustrated by graphs according to Monte Carlo simulation. A new algorithm based on the Monte Carlo method is presented to determine the reactivity ratios, i.e., the reactivity ratios are obtained by comparison of the data simulated from random simulation of chain propagation of copolymerization with the experimental data. Moreover, the alkoxylation reaction kinetics is investigated by the Monte Carlo method. These results of simulation are in good agreement with the experiment.The thermal degradation kinetic parameters are calculated from the TG-DTG curves of polyethers, and the most probable mechanism functions are obtained by the universal integral and differerntial equation methods. The thermal stability of polyethers is investigated by the thermal degradation temperature and the thermal lifetime equations, and the effect of thermal atmosphere, copolyether types, initiator, monomer units’ ratios and molecular weight on the thermal stability is revealed. Moreover, the quantum chemical method is employed to calculate the molecular parameters of polyether model compounds and the degradation mechanism of polyether is analyzed theoretically. Based on the identification of intermediates and products of polyether thermal degradation by GPC and NMR, the thermal degradation scheme is proposed, i.e., the thermal degradation proceeds through a random bond cleavage of C-0 and C-C of polyether backbone chain while the thermal oxidative degradation proceeds through a complicated radical bond cleavage of polyether peroxide.Finally, the surface activity of dodecyl and tridecyl block copolyether nonionicsurfactants (RPE) is studied. A linear decrease of ln[CMC] vs the number of oxypropylene units in the copolymer molecule is observed. Furthermore, the penetrating quality of RPE block copolyether is studied and the effect of initiator structures and monomer units’ ratios is revealed.As far as know, the above mentioned results concerned the research on the mechanism of ring-opening polymerization by quantum chemical methods, the simulation of the copolymerization by Monte Carlo method, the research on the thermal degradation (kinetics, degradation temperature and lifetime equations) of polyethers by TG-DTG method have not been seen in the literature.更多还原