| Carbon dioxide (CO2) is the only carbon source of all the biomass and can transform to the carbohydrate through photosynthesis, but excessive CO2 from industrial emission leads to the greenhouse effect. Therefore, recycling CO2 and chemical fixation of CO2 are receiving increased attention. It is very attractive to establish the synthetic methodology of using CO2 as starting material for the synthesisi of small organic molecular and especially polymer. The coupling of epoxide and CO2 to produce the biodegradable polycarbonate has been regarded as the most promising method, which was first reported by Inoue and his coworkers in 1969. Although there is growting effort to develop the effective catalyst for the copolymerization of CO2 and epoxide, some problems still plague these catalyst systems, such as low catalyst activity, inferior polymer selectivity, irregular region- and stereo- chemistry and so on.In this dissertation, it have designed and synthesized a series of chiral Schiff base tetradonta cobalt complexes as electrophilic reagents to systematically study the structure of the catalyst on the copolymerization CO2/PO impact, from the spatial structure and electronic effects on polymerization.On this basis, it is proposed a law to design a dual function of high activity polymerization and catalyst system and then to optimize the CO2 and PO highly efficient catalytic system which is asymmetry, regional and stereoselective. In this paper, It is first reported the crystal structure of salenCoIII-OPh (NO2) 2 complex. The crystal structure shows that this kind of complexes was the hexa-coordinate. Their configuration was octahedral structures. And Lewis base[PPN]Cl as the main catalyst, Schiff base-cobalt complexes catalyzed CO2 and rac-PO alternating copolymerization, which had a good control and stereoselective. The study found that the length of the bridge on amine CO2 and rac-PO alternating copolymerization of a clear impact. For two different synthetic compounds, when the length of the amine bridge is 2, TOF values 454 h-1. However, when the length of the amine bridge changes into a 3 carbon atoms, TOF values rapidly decreased to 95 h-1. It can be seen that the shorter length of the amine bridge will be conducive to the improvement of activity. At the same time, It have little effect on the molecular weight if increase the selectivity of PPC but increased polycarbonate head to tail units content for two different compounds with the two methyl substituents. For the Chiral amines bridge, head to tail linked units content of the polycarbonate has improved. Compare to non-splited diaminocyclohexane, the content of head to tail linked units of the plited diaminocyclohexane increased 20%. The structure of diaminocyclohexane is Chair-type, which has an additional steric and also increases the coordination of space in another position. It shows a high catalytic activity and better selectivity of the region, so that head to tail linkage units increase to 96%. It has obtained that the electron had a significant impact of steric effects on the catalytic activity, so as the Steric to the selectivity of the polymerization. The axial group is obvious as well. In the same reaction conditions, the bigger the catalyst acidic groups axial, the better the effect of chiral induction. It is CC13COO->CF3COO-> CH3COO-> Cl-. It coincides with the order of the group size. The largest axial steric group of complexes and [PPN] Cl as the catalysts reacted in 30oC. And then head to tail linked units of the propylene carbonate content will be 96%. When the axial group changed into the C1- thar has the smallest steric, the content of head to tail linked units of the product decreased to 88%.In the salen structure the nature of substituents of the benzene have a great impact of the catalytic activity and selectivity of legislation. The larger of the group R1 in the benzene, the higher of the selectivity of the catalyst. When the substituent R1 is tert-butyl, it showed the highest selectivity. But as the substituent increased, polymerization rate will decreased. Introduce the ligand electron substituent to the schiff base can enhance the catalytic activity to a large extent.And further clarified that the production of the polymer, selectivity of the polycarbonate and cyclic carbonate (PPC / PC), polymer molecular weight, and the relationship between the content of head to tail units and catalyst structure. It is pay close attention to the study of CO2 and epoxides in the copolymerization.Co-catalyst, the ratio of between co-catalyst and catalyst, polymerization temperature, time, CO2 pressure are also very important factors, which further affect the performance of the polymer. In this paper, it had an in-depth study on this area. Using the Schiff-base to catalyze the copolymerization of CO2 and rac-PO, it has deeply studied on the catalyst activity and the stereoselectivity. It has discussed changing the reaction temperature, polymerization pressure, and the ratio of co-catalyst and catalyst. And further study of the relationship between the external conditions of polymerization and catalyst activity and stereoselectivity. Firstly, with (PPN) Cl as the cocatalyst, SalenCoIII (OOCR) catalyzed the alternating copolymerization between CO2 and rac-PO successfully. By testing the Polymer through NMR, IR, DSC and other means of test, the result showed that the polymer was completely alternating polycarbonate, which demonstrated a better selectivity between polycarbonate and cyclic carbonate. The content of head to tail linked units of the polymer was up to 95% and molecular weight was up to 72,500. Secondly, this article discussed the effects of polymerization under the CO2 pressure in details. When the pressure was more than 30Pa, the content of the carbonate in the polymer had little change. While when the pressure was less than 30 Pa, the content of the carbonate unit had increased with the pressure increased. Polymerization pressure had little effect on the conversion rate of PO. Thirdly, when the polymerization temperature increased from 50 oC to 80 oC, the polymer yield increased obviously and had a little change more than 80 oC. With increasing temperature, polymer molecular weight has decreased. When the temperature increased from 50 oC to 90 oC, there was little change on the content of carbonic anhydrase. Its value was between 95.6%~ 96.9%. At last, with prolonged the time, the reaction rate increased at the beginning, then decreased and finally remained basically unchanged. At 80 oC, the initial reaction rate was maximum, then decreased, and finally also changed little.
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