Synthesis And Depolymerization Study Of Recyclable CO₂-based Polycarbonate

Modern life relies on polymers,from the materials that are used to make clothing,houses,cars and aeroplanes to those with sophisticated applications in medicine,diagnostics and electronics.The vast majority of these polymers are derived from petrochemicals,which not only leads to the depletion of resources,but also accompanies with environmenatal problems.Therefore,it is important to develop the sustainable polymer materials derived from renewable resources.CO₂ is a renewable,non-toxic,abundant sources resourc,and has become an excellent chemical raw material.In many studies of CO₂,its reaction with alkylene oxide to produce CO₂ based polycarbonate has good application prospects.However,the widely used polycarbonate can not be recycled through chemical degradation.Therefore,it is very meaningful to develop a recyclable CO₂-based polycarbonate.This article focuses on the development of recyclable alkylene oxide substrates and the effects of ring structure on the reactivity,stereoselectivity,and degradability of CO₂-based polycarbonates.We have designed and prepared a series of five-membered ring-containing nitrogen-containing alkylene oxide monomers for copolymerization with CO₂ using dinuclear Co???-Salen complex in conjunction with PPN-X?PPN=bis?triphenylphosphine?iminium,X=2,4-dinitrophenoxide?.We compare the differences in the thermodynamic properties of polycarbonates obtained from different substituents on nitrogen.It is found that under certain conditions,polymers with different substituents can be completely degraded in neat and in solution.By examining the molecular weight change during the degradation process,it was found that the degradation process is accompanied by the occurrence of chain scission.The dinuclear Co???-Salen complex in conjunction with PPN-X is a highly efficient catalyst for the desymmetrization copolymerization of CO₂ with cycloheptene oxide.We investigate the effects of temperature,concentration and catalysts with different structures on the asymmetric copolymerization reaction with CO₂.The thermal study suggest that the high stereoregular CO₂-based polycarbonate has a T_m of 247 ^oC,while its atactic copolymer has a T_g of 93 ^oC.And we systematically studied the effects of ring structure on the alternating copolymerization activity,enantioselectivity,polymer crystallinity and degradability of alkylene oxide and CO₂.