Crosslinking 1,4-polybutadiene via allylic amination: a new strategy for deconstructable rubbers

Abstract

As post-consumer rubbers (e.g., car tires) continue to accumulate in landfills and the environment, there is an increasing need for more reprocessible materials. Traditionally, devulcanization of rubbers requires excessive energy and releases toxic byproducts. Accordingly, downcycling (e.g., crumb rubber for asphalt or turf) is the major avenue for end-of-life thermoset elastomers. To enable alternative recycling pathways, herein we propose a two-step procedure to crosslink polybutadiene (PBD) as a substitute for vulcanization, resulting in deconstructable soft materials. First, we utilize the established C–H allylic amination of PBD to access thermoplastic elastomer pre-polymers functionalized with electrophilic hexafluoroisopropyl sulfamate (PBD-HFIPS). Then, PBD-HFIPS alcoholysis with diol crosslinkers yields thermoset specimens with tunable thermal, rheological, and mechanical properties dependent on crosslinker identity and density. Finally, treating these thermosets with a nucleophile cleaves sulfamate crosslinks and regenerates the thermoplastic with no characterizable differences from virgin PBD.