Microstructures Research Of Copolymer From Styrene Oxide And CO₂

Utilization and capture of carbon dioxide (CO2) has become a strategic research topic which drew much worldwide attentions. The alternating copolymerization of epoxides and CO2produce biodegradable polycarbonates is one of the most attractive processes for the transformation of CO2due to its economic and environmental benefits. The catalytic synthesis of polycarbonates with high molecular weight and high carbonate linkages is one of the most important issues, while the accurate control of polymer properties and its stereochemistry remains challenge. This dissertation focuses on the asymmetric regio-and stereo-selective alternating copolymerization of styrene oxide and CO2with emphasis of regio-and stereochemistry, and thermodynamic properties.Concerning on the issue that micro structures (regio-and stereo-chemistry) of copolymer from styrene oxide and CO2have not been identified clearly, three kinds of model compounds bearing different linkages were synthesized from racemic2-methoxy-2-phenylethanol and2-methoxy-1-phenylethanol. Therefore, the regional regularity of the copolymer from styrene oxide and CO2was characterized explicitly by the13C NMR studies of those model compounds. Ten kinds of model compounds with different stereochemistry were synthesized to simulate carbonate unit sequence using chiral2-methoxy-2-phenylethanol and2-methoxy-1-phenylethanol as substrates, which prepared by hydrolytic kinetic resolution of racemic styrene oxide and then protection of the hydroxyl groups. The13C NMR studies of those model compounds provided a data platform to test the microstructures of copolymer from styrene oxide and CO2.A binary catalyst systems with a SalenCo(III)X complex in which bi(2-naphthol) and bulky sterically hindered adamantyl group were anchored on the ligand framework as catalyst and PPN-DNP as cocatalyst was developed. This catalyst system showed promising activity toward asymmetric regio-and stereo-selective alternating copolymerization of (R)-styrene oxide and CO2under mild conditions. According to the above-established data of microstructural characterization, the synthesized poly (styrene carbonate) has92.2%head-to-tail content and a highly regioregular ring-opening step was observed with a concomitant96.0%retention of configuration. The thermal deformation ability of the above poly (styrene carbonate)(Tg=90℃) has been improved compared with atactic poly (styrene carbonate)(Tg=80℃).