Polymer re-use has been deemed highly critical for improving plastics circular economy and environmental sustainability. Chemical recycling has attracted increasing interests due to its capability of degrading polymers to precursors and building blocks, which could be used as feedstocks similar to petroleum-based chemicals. Although there are several approaches towards creating novel recyclable polymers via introducing cleavable or dynamic linkers, existing thermoset polymers have been widely overlooked since they are considered as permanently bonded materials. Herein, by performing the retrosynthetic analysis of a traditional polycyanurate (PCN) thermoset, we redirected the synthetic route from conventional C-N bond formation via irreversible cyanate trimerization to constructing the C-O bonds through reversible nucleophilic aromatic substitution (S<sub>N</sub>Ar) between alkoxyl triazine and alcohol (Figure1). Our approach for polycyanurate synthesis overcomes a number of limitations in traditional trimerization approach, including the substrate scope limited only to aryl monomers, high reaction temperature, and the difficulty of remolding, repairing, and recycling. Previously inaccessible alkyl-polycyanurate thermosets have been successfully prepared, which show excellent film properties with high chemical resistance under various conditions, and closed-loop polymer-to-polymer recyclability. Our results reveal that revisiting the chemical structures of traditional thermosetting polymers, assisted with retrosynthetic analysis, could lead to discoveries of “apparently dormant” dynamic linkages. Utilizing those dynamic linkages to construct the same type of polymer network would significantly expand the monomer scope and enable sustainable features for traditionally non-recyclable materials, without sacrificing their physical properties.

Recyclable and malleable thermosets enabled by dynamic nucleophilic aromatic substitution

Where thousands of chemistry professionals meet to share ideas and advance scientific and technical knowledge. Spring 2023 abstracts, posters, and presentations will launch at the end of March.

ACS Spring 2023

The official archive and repository for all ACS Meetings & Expositions abstracts and select posters or presentations.