| Sustainable development is an important factor to be considered in the development of world's economy and technology.Replacemant of the fossil energy with renewable energy is an important object.Carbon dioxide is an abundant,renewable,non-toxic resource that makes it a great starting material.Among various reactions for CO2 transformation,the alternating copolymeration of CO2 and epoxides to produce CO2-based polycarbonates has received much attention due to its important research and application prospects.The biodegradability and non-toxicity of CO2-based polycarbonate make it a promising material.The thesis mainly focuses on designing a novel epoxide for preparation of completely recyclable and crystalline CO2 based polycarbonate.The epoxide,1-benzyloxycarbonyl-3,4-epoxy pyrrolidine?BEP?,was synthesized and used as monomer for copolymerization with CO2 using binary catalyst system of dinuclear Cr?III?-Salen complex in conjunction with PPN-X?PPN= bis?triphenylphosphine?iminium?It was discovered that the axial anion of the complex,reaction temperature,CO2 pressure significantly determine the product selectivity and reaction activity.The optimum polymerization conditions were obtained.The study on the depolymerization process of polycarbonate both in bulk and solution show the starting epoxide is the sole product of the depolymerization.The dinuclear chiral Co?III?-Salen complex in conjunction with PPNDNP?PPN= bis?triphenylphosphine?iminium,X=2,4-dinitrophenoxide?was effective catalyst system for the asymmetric copolymerization of CO2 with meso-1-benzyloxycarbonyl-3,4-epoxy pyrrolidine to produce isotacticity CO2-based polycarbonate.The steric hinderance of substituent groups on bimetallic catalyst,reaction temperature and reaction solvent are important factors to determine the reaction activity and enantioselectivity.The thermal study suggest that the high stereoregular CO2-based polycarbonate is a semi-crystalline polymer which possesses a Tg of 107 oC and Tm of 173 oC. |
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