Making Polycarbonates From CO₂and Epichlorohydrin By Stereoselective Copolymerization

With the dwindling of fossil resources and the increasing of global greenhouse effect, low-carbon economy and strategy of sustainable development has already being taken seriously. CO2as a raw material used to build large molecules polymer, especially the production of biodegradable polycarbonate copolymers has been regarded as the most promising green polymerization process. Since the first example was reported in1969, the polymer selectivity, reactivity, and mechanism have made significant gains during the epoxides/CO2copolymerization. Although tremendous progress has been made over the past decade, they are generally associated with polycarbonate formation from aliphatic terminal epoxides or cyclohexene oxide derivatives. Very limited literature exists concerning the synthesis of CO2copolymers from epoxides with electron-withdrawing groups such as styrene oxide and epichlorohydrin. On the other hand, the mechanical properities of the polymer are determined by the configuration of the regular alternating units. Generally, the stereospecific polymers often display superior mechanical and thermal properties compared to their atactic analogs For CO2/epoxides copolymerization, it is very important for the accurate control of the regioselective ring-opening and stereochemistry during the epoxide nng-openning process.In order to solve above-mentioned problems, in this dissertation, on the basis of the previous research about copolymerization of epoxides/CO2,we focus on the easily obtainable raw material, epichlorohydrin, the catalytic system with chiral center and reaction conditions was optimized. Herein, we scuessfuly make highly stereospecific alternating ECH/CO2copolymer (97%stereoselectivity) by utilizing multi-chiral bifunctional cobalt-salen catalysts. On this basis, further study about the catalysts and reaction conditions making influence on the chiral epichlorohydrin’s regioselective ring-opening were performed. In addition, with chiral binary-cobalt-salen catalyst, expecially experiments focusing on the ring-opening at both the methylene and methine carbons and stereochemistry retention ratio occurs were also performed. The regioselectivity of epoxide ring-opening is dependent not only on the catalyst structure but also the reaction temperature. At the same time, the mechanical properties of the ECH/CO2copolymer polymer were frist studied.