Selectively Depolymerizable Polyurethanes from Unsaturated Polyols Cleavable by Olefin Metathesis

This communication describes a novel series of linear and crosslinked polyurethanes (PUs) and their selective depolymerization under mild conditions. Two unique polyols are synthesized bearing unsaturated units in a configuration designed to favor ring‐closing metathesis (RCM) to five‐ and six‐membe...

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Bibliographic Details
Published in:Macromolecular rapid communications. 2021-02, Vol.42 (4), p.e2000571-n/a
Main Authors: Jones, Brad H., Staiger, Chad, Powers, Jackson, Herman, Jeremy A., Román‐Kustas, Jessica
Format: Article
Language:English
Subjects:
Catalysts
Condensates
Condensation polymerization
Crosslinking
cycloalkenes
Depolymerization
Isocyanates
Low molecular weights
Metathesis
Molecular weight
olefin metathesis
Organic compounds
Polymerization
Polymers
Polyols
Polyurethane
polyurethanes
ring‐closing metathesis
Toluene
Toluene diisocyanate
Toluene diisocyanates
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Summary:This communication describes a novel series of linear and crosslinked polyurethanes (PUs) and their selective depolymerization under mild conditions. Two unique polyols are synthesized bearing unsaturated units in a configuration designed to favor ring‐closing metathesis (RCM) to five‐ and six‐membered cycloalkenes. These polyols are co‐polymerized with toluene diisocyanate to generate linear PUs and trifunctional hexamethylene‐ and diphenylmethane‐based isocyanates to generate crosslinked PUs. The polyol design is such that the RCM reaction cleaves the backbone of the polymer chain. Upon exposure to dilute solutions of Grubbs’ catalyst under ambient conditions, the PUs are rapidly depolymerized to low molecular weight, soluble products bearing vinyl and cycloalkene functionalities. These functionalities enable further re‐polymerization by traditional strategies for polymerization of double bonds. It is anticipated that this general approach can be expanded to develop a range of chemically recyclable condensation polymers that are readily depolymerized by orthogonal metathesis chemistry. Linear and crosslinked polyurethanes are prepared from traditional isocyanates and new polyols containing unsaturated moieties designed to favor ring‐closing olefin metathesis and concomitant cleavage of the molecule. These polyurethanes are found to be efficiently depolymerized upon exposure to second generation Hoveyda–Grubbs catalyst under ambient conditions. The depolymerization products are multi‐vinyl/cycloalkene species that can be re‐polymerized.
ISSN:1022-1336
1521-3927
DOI:10.1002/marc.202000571