A variety of new dinuclear zinc catalysts was developed and tested for the copolymerization of cyclohexene oxide and carbon dioxide. Electron-withdrawing groups thereby led to unprecedented activities with turnover frequencies up to 155,000 h(-1). These are by far the highest polymerization rates ever reported for the copolymerization of cyclohexene oxide and CO2.
The present study is one of the first examples for rare earth metal-mediated group transfer polymerization (REM-GTP) with non-metallocene catalyst systems. 2-Methoxyethylaminobis(phenolate)yttrium trimethylsilylmethyl complexes were synthesized and showed moderate to high activities in the rare earth metal-mediated group transfer polymerizations of 2-vinylpyridine, 2-isopropenyl-2-oxazoline, diethyl vinylphosphonate, diisopropyl vinylphosphonate, and N,N-dimethylacrylamide as well as in the ring-opening polymerization of β-butyrolactone. Reaction orders in catalyst and monomer were determined for the REM-GTP of 2vinylpyridine. The mechanistic studies revealed that the catalyst systems follow a living monometallic group transfer polymerization mechanism allowing a precise molecular-weight control of the homopolymers and the block copolymers with very narrow molecular weight distributions. Temperaturedependent reaction kinetics were conducted and allowed conclusions about the influence of the bulky substituents around the metal center on the polymerization activity. Additional polymerization experiments concerning the combination of REM-GTP and ROP to obtain block copolymers were performed.
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