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Edited by Miguel A. Garcia-Garibay, University of California, Los Angeles, CA, and accepted by Editorial Board Member R. D. Levine May 19, 2016 (received for review January 18, 2016)
Significance
This work describes a convenient, quantitative, and robust one-step transformation of polycarbonates into high-value poly(aryl ether sulfone)s in the presence of a carbonate salt and bis(aryl fluorides). This strategy has important implications for the repurposing of plastic waste into value-added materials by the use of carefully controlled depolymerization conditions. Computational studies used to support these findings show how carbonate salts decompose organic carbonates and form the poly(aryl ether sulfone) products. Determining the role of the metal salt in the depolymerization/repolymerization process will enable future design for economic recycling and synthesis methods.
Abstract
It is estimated that ∼2.7 million tons poly(carbonate)s (PCs) are produced annually worldwide. In 2008, retailers pulled products from store shelves after reports of bisphenol A (BPA) leaching from baby bottles, reusable drink bottles, and other retail products. Since PCs are not typically recycled, a need for the repurposing of the PC waste has arisen. We report the one-step synthesis of poly(aryl ether sulfone)s (PSUs) from the depolymerization of PCs and in situ polycondensation with bis(aryl fluorides) in the presence of carbonate salts. PSUs are high-performance engineering thermoplastics that are commonly used for reverse osmosis and water purification membranes, medical equipment, as well as high temperature applications. PSUs generated through this cascade approach were isolated in high purity and yield with the expected thermal properties and represent a procedure for direct conversion of one class of polymer to another in a single step. Computational investigations performed with density functional theory predict that the carbonate salt plays two important catalytic roles in this reaction: it decomposes the PCs by nucleophilic attack, and in the subsequent polyether formation process, it promotes the reaction of phenolate dimers formed in situ with the aryl fluorides present. We envision repurposing poly(BPA carbonate) for the production of value-added polymers.
Footnotes
- ↵1To whom correspondence may be addressed. Email: gojones{at}us.ibm.com or jmgarcia{at}us.ibm.com.
Author contributions: J.L.H. and J.M.G. designed research; G.O.J., A.Y., R.J.W., and J.M.G. performed research; G.O.J., J.L.H., and J.M.G. analyzed data; and G.O.J. and J.M.G. wrote the paper.
The authors declare no conflict of interest.
This article is a PNAS Direct Submission. M.A.G.-G. is a guest editor invited by the Editorial Board.
This article contains supporting information online at www.pnas.org/lookup/suppl/doi:10.1073/pnas.1600924113/-/DCSupplemental.
Conversion of poly(carbonate)s into poly(ether)s
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