A highly active enantiopure bimetallic cobalt complex was explored for the enantioselective polymerization of a variety of monosubstituted epoxides. The polymerizations were optimized for high rates and stereoselectivity, with s-factors (kfast/kslow) for most epoxides exceeding 50 and some exceeding 300, well above the threshold for preparative utility of enantiopure epoxides and isotactic polyethers. Values for mm triads of the resulting polymers are typically greater than 95%, with some even surpassing 98%. In addition, the use of a racemic catalyst allowed the preparation of isotactic polyethers in quantitative yields. The thermal properties of these isotactic polyethers are presented, with many polymers exhibiting high T m values. This is the first report of the rapid synthesis of a broad range of highly isotactic polyethers via the enantioselective polymerization of racemic epoxides. © 2010 American Chemical Society.
Bibliographical noteKAUST Repository Item: Exported on 2020-10-01
Acknowledged KAUST grant number(s): KUS-C1-018-02
Acknowledgements: We thank the NSF (CHE-0809778), King Abdullah University of Science and Technology (KAUST; Award No. KUS-C1-018-02), and Sumitomo Chemicals for support. This research made use of the Cornell Center for Materials Research Shared Experimental Facilities supported through the NSF MRSEC program (DMR-0502404). R.M.T. acknowledges a Hunter Rawlings Cornell Presidential Research Scholarship. We thank Mr. Tom Mourey and Ms. Lisa Slater for GPC analysis of poly(1,1,1-trifluoro-2,3-epoxypropane) and Dr. Ivan Keresztes for assistance with the NMR analysis of 3.
This publication acknowledges KAUST support, but has no KAUST affiliated authors.