Cobaltoporphyrin-Catalyzed CO 2 /Epoxide Copolymerization: Selectivity Control by Molecular Design

Anderson, Carly E.; Vagin, Sergei I.; Xia, Wei; Jin, Hanpeng; Rieger, Bernhard

Cobaltoporphyrin-Catalyzed CO 2 /Epoxide Copolymerization: Selectivity Control by Molecular Design

Type

Article

Authors

Anderson, Carly E.
Vagin, Sergei I.
Xia, Wei
Jin, Hanpeng
Rieger, Bernhard

KAUST Grant Number

UK-C0020
KSA-C0069

Online Publication Date

2012-08-21

Print Publication Date

2012-09-11

Date

2012-08-21

Abstract

A series of cobalt(III) chloride porphyrin complexes of the general formula 5,10,15,20-tetra(p-alkoxy)phenylporphyrin cobalt chloride (4b-e) and the related 5,10,15,20-tetra(p-nitro)phenylporphyrin cobalt chloride (4f) are presented and their reactivity toward propylene oxide (PO)/CO 2 coupling/copolymerization is explored. While the nitro-substituted complex (4f), in conjunction with an onium salt, shows moderate activity toward cyclization, the 4b-e/onium systems show superior copolymerization activity in comparison to tetraphenylporphyrin Co(III) chloride (4a) with high selectivity and conversion to poly(propylene carbonate) (PPC). A comprehensive copolymerization behavior study of the alkoxy-substituted porphyrin complexes 4b-e in terms of reaction temperature and CO 2 pressure is presented. Complexes bearing longer alkoxy-substituents demonstrate the highest polymerization activity and molecular weights, however all substituted catalyst systems display a reduced tolerance to increased temperature with respect to PPC formation. Studies of the resulting polymer microstructures show excellent head-to-tail epoxide incorporation and near perfectly alternating poly(carbonate) character at lower polymerization temperatures. © 2012 American Chemical Society.

Citation

Anderson CE, Vagin SI, Xia W, Jin H, Rieger B (2012) Cobaltoporphyrin-Catalyzed CO 2 /Epoxide Copolymerization: Selectivity Control by Molecular Design . Macromolecules 45: 6840–6849. Available: http://dx.doi.org/10.1021/ma301205g.

Acknowledgements

We gratefully acknowledge the King Abdullah University of Science and Technology (KAUST), Award No. UK-C0020, KSA-C0069, for financial support. Ms. A. Jonovic is thanked for technical support with TGA and GPC measurements. Mr. V. Bretzler is acknowledged for helpful comments with the preparation of this manuscript.