Crosslinked polymers, or thermosets, comprise approximately 20 percent of all plastics manufactured globally. In most cases, the chemical crosslinks that provide thermosets with their desirable shape retention, mechanical performance, and thermal stability come at the cost of reprocessability and degradability, ultimately contributing to the buildup of plastic waste. Polyurethanes (PUs) are one of the largest classes of thermosets produced, with applications spanning coatings, adhesives, composites, and foams. Unlike typical thermosets, the most common PUs are derived from aromatic diisocyanates crosslinked with alcohol-bearing, low-T<i><sub>g</sub></i> polymers (polyols); these materials have an inherent thermal degradability and reprocessability enabled by the equilibrium between free isocyanates, alcohols, and urethane (carbamate) linkages. However, for certain high-performance applications that demand greater thermal stability, photostability, and optical clarity, aromatic isocyanates must be replaced with aliphatic variants. These non-aromatic PU materials are much less amenable to reprocessing and generally cannot be deconstructed to useful products due to decomposition at the higher temperatures required to induce exchange of the less reversible alkyl carbamate linkages. We have recently developed a simple “drop-in” additive strategy to imbue non-aromatic PU thermosets with deconstructability and reprocessability at low additive loading. A small library of bifunctional cleavable comonomers was designed, synthesized, and introduced at variable loading to polyurethane formulations to generate new crosslinked polyurethane thermosets. The cleavable monomer bonds were shown to be chemoselectively deconstructable under mild conditions and could be used to yield re/up-cyclable PU network fragments for downstream applications.

Cleavable additives enable on-demand degradable non-aromatic polyurethanes

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ACS Fall 2022

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