| Polycarbonates, an environmentally friendly material, can be got by the copolymerization of CO2and epoxides. However, catalysts of higher activity and polymers with various structures are eagerly desired.Among the catalysts of CO2/aliphatic epoxides copolymerization, zinc catalysts including homogeneous and heterogeneous catalysts own outstanding properties:low toxicity, reasonable price, light color and suitability for a large scale of epoxides. But the low activity hinders their further application. Therefore, zinc-bis(phenoxide) complexes and β-diimiante-zinc catalysts bearing a cyano group on the ligand framework separatively have been designed for the alternating copolymerization of CO2and cyclohexene oxide (CHO) in order to improve the activity of zinc catalysts. The activity of the newly designed zinc-bis(phenoxide) catalyst which is up to22.8h-1is much higher than that of the zinc-bis(phenoxide) complex without a cyano group (9.6h-1). However the activity of β-diimiante-zinc catalysts with a cyano group is not good (up to3.3h-1) because of the instability of the ligand’s asymmetric structure.Block copolymers usually own outstanding properties because they consist of different polymer chains. Therefore, a series of CO2-based polycarbonates block polymers have been synthesized using hydrogen-terminated polystyrene (PS) and1,2-polybutadiene (PB) as macro initiators. Propylene epoxides (PO),1,2-epoxybutane (BO) and1,2-epoxyhexane (HO) copolymerize with CO2catalyzed by SalenCo(Ⅲ)NO3with1,5,7-triazabicyclo[4.4.0] dec-5-ene (designated as TBD, a sterically hindered organic base) anchored on the ligand framework at25℃and2.0MPa CO2pressure successively and finally we get PS-b-PPC diblock copolymers and PPC-b-PS-b-PPC and PPC-b-PB-b-PPC triblock copolymers, which enrich the structures of CO2-based copolymers. What’s more, because of the polycarbonate units, the resulting polymers can be partly biodegradable which makes them useful in polymer memory materials. |
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