Synthetic Investigation And Theoretical Research By Quantum Chemistry Methods Of Propylene Oxide Ring-opening Esterification

The advantages of ring-opening polymerization between maleic anhydride and propylene oxide lies in no water production during the reaction , low energy requirement for its charactersitc of exothermic reaction and successive reaction .The production can be changed by methods of etherification , acidification , sulfonation , etc .In this thesis, the ring-opening polymerization mechanism of maleic anhydride and propylene oxide , the polymerization process and the energy variation were studied using quantum chemical methods to develop high quality polymerization products and improve the unsaturated polyester production .Quantum chemical methods were employed to investigate the mechanism of ring-opening polymerization of Maleic anhydride and Propylene oxide. Firstly, optimization the structures of Maleic anhydride and Propylene oxide were studied by RHF/6-31G, RHF/6-31G+,and B3LYP/6-31G ,and B3LYP/6-31G+ methods. Compared calculation with the experimental data , the structure given by B3LYP/6-31G method is better than others. And then the reaction mechanism of ring-opening polymerization of Maleic anhydride and Propylene oxide was discussed at microscopic electronic density level . Furthermore,the specific steps of polymerization reaction of Maleic anhydride and Propylene oxide was guessed and calculated by B3LYP/6-31G+ method. All the transition states were verified by the vibrational analysis and the IRC calculations. The mechanism of the reaction was confirmed,and the activation energies were gained. The results show that the reaction was exothermic, it matches up well with experiment.The IR and NMR spectra of products P2 and P4 were achieved by quantum chemical calculations. Comparisons of calculated spectra with experimental spectra of the unsaturated polyester show similar peak shape and wavenumbers of C=O and C=C stretching vibration in IR spectra, and also show similar chemical shifts of C=C and CH3 groups in NMR spectra, which results the guess and calculation of ring-opening polymerization between maleic anhydride and propylene oxide are accurate.The polymerization kinetics of maleic anhydride and propylene oxide was studied from the microscopic and macroscopic aspects. The theoretical product distribution was deduced under full consideration of the initiation, propagation, chain transfer, proton exchange reactions, and the most widely used theoretical distribution models, the cationic ring-opening polymerization of ethylene oxide proceeds by nucleophilic attack of the secondary alcohol propagating anion on monomer. Calculation results could explain the experimental facts satisfactorily.