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DOI: 10.1002/adma. 201601242 reversible reactions, such as retro-Diels–Alder,[14–17] reversible radical association–dissociation,[18–20] reversible click chemistry,[21] disulfide metathesis,[22–24] transalkylation,[25] boronic ester exchange,[26] and transcarbamoylation [27] have also been reported in the design of malleable crosslinked polymeric materials. However, most of them are limited by the availability of commodity raw materials.

Crosslinked polyurethanes and polyureas that are synthesized from multifunctional isocyanates and alcohols or amines with 100% atomic conversion have been proven to qualify as high-performance polymeric materials with low cost. However, they also suffer from the lack of processing and recycling because of the extremely stable urethane or urea.[27] Recently, we reported that by introducing bulky substituents on one of the nitrogen atoms of a urea bond, the resulting hindered urea bonds (HUB) show a dynamic nature under ambient/catalyst-free conditions.[28, 29] Hindered urea bond (HUB)-based soft organogels with low crosslinking density showed efficient self-healing properties. Here, we report a new class of hard poly (urea-urethane) thermosets based on HUB that behave like classic thermoset at ambient conditions yet can be reprocessed by application of heat and recycled from a mixture of traditional thermoplastics and thermosets.