(Co)polymerization of six-membered cyclic carbonates over coordinating catalysts
Polimery 2001, No 9, 602
SummaryCoordination polymerization of 6-membered trimethylene carbonate and neopentyl carbonate was studied in the presence of organoaluminum, organozinc and organotin catalysts. Methylaluminoxane, tin(II) 2-ethylhexanoate and products of reactions of triethylaluminum with water, diethylzinc with water, and diethylzinc with pyrogallol were used as the coordinating catalysts. Polymerizations were run at 30-60°C to yield oligocarbonates, M = 2000-45 000 g/mol, in 50-95% yields (Table 1). The catalysts used enabled copolymers of 6-membered carbonates and propylene oxide (Table 2), propylene carbonate (Table 4) and terpolymers with propylene oxide and carbon dioxide (Table 3) to be prepared. The number-average M of the copolymers and terpolymers ranged from 1500 to 13 500 g/mol. Each comonomer used was less reactive than trimethylene carbonate and neopentyl carbonate. Copolymerization with propylene carbonate should be run at temperatures of min. 80oC; under these conditions, carbonate groups become partially decarboxylated (eqn. 12). The present and the reported results were used to discuss certain aspects of the propagation mechanism involving alkoxide or carbonate active centers.