Base initiated depolymerization of polycarbonates to epoxide and carbon dioxide co-monomers: a computational study.
- Resource Type
- Article
- Authors
- Darensbourg, Donald J.; Yeung, Andrew D.; Wei, Sheng-Hsuan
- Source
- Green Chemistry. 2013, Vol. 15 Issue 6, p1578-1583. 6p.
- Subject
- *DEPOLYMERIZATION
*POLYCARBONATES
*EPOXY compounds
*CARBON dioxide
*MONOMERS
*ALKOXIDES
*ISOCYANIDES
- Language
- ISSN
- 1463-9262
High-accuracy CBS-QB3(+) calculations were used to obtain the free energy barriers for several polycarbonates of interest to undergo alkoxide back-biting to give the corresponding epoxide and carbon dioxide. Free energy barriers to epoxide formation were modest for most polymeric alkoxides (12.7–17.4 kcal mol−1), and they were higher than for the same starting material to give cyclic carbonate (10.7–14.6 kcal mol−1). Poly(cyclopentene carbonate) differs: epoxide formation has a lower free energy barrier (13.3 kcal mol−1) than cyclic carbonate formation (19.9 kcal mol−1). These results explain why poly(cyclopentene carbonate) depolymerizes to cyclopentene oxide when treated with a strong base, whereas propylene and styrene polycarbonates depolymerize to their respective cyclic carbonates. Recycling via regeneration of the monomer represents the ideal method for producing material of the highest quality. [ABSTRACT FROM AUTHOR]