Selective, Simultaneous, and Sequential Deconstruction Strategies for Isocyanate Regeneration from Polyureas, Polyurethanes, and Their Mixtures

Isocyanate recovery from end-of-life polyureas (PUEs), polyurethanes (PUs), and polyurethane-ureas (PUUEs) offers a potential route to valuable chemical feedstocks and reduced reliance on hazardous, economically burdensome, phosgene-based manufacturing. Herein, we report a deconstruction platform that regenerates isocyanates from PUEs/PUs/PUUEs under mild conditions (60 °C, 1 atm). Our approach leverages a Lewis-acid-driven deconstruction strategy in which thionyl chloride and B-chlorocatecholborane selectively cleave urea and urethane linkages, respectively, to regenerate isocyanates. Through this methodology, we demonstrate three deconstruction modes: (i) selective isocyanate regeneration from PUEs or PUs, (ii) simultaneous deconstruction of PUUEs and PUE/PU mixtures, and (iii) sequential reagent addition and deconstruction that directs isocyanate regeneration from urea or urethane linkages within mixed polymer streams. Recovered isocyanates were used to prepare second-generation PUEs and PUUEs with molecular weights and thermal properties comparable to the virgin counterparts. Overall, this work presents a deconstruction framework with controlled access to isocyanates and provides a foundation for future recycling strategies for PUEs, PUs, and PUUEs.