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

Area of Science:

• Polymer Chemistry
• Materials Science
• Sustainable Chemistry

Background:

• Growing accumulation of post-consumer rubber waste, like car tires, necessitates advanced recycling solutions.
• Conventional rubber devulcanization is energy-intensive and produces hazardous byproducts, limiting recycling options to downcycling.
• Thermoset elastomers, while durable, are difficult to reprocess, posing significant end-of-life challenges.

Purpose of the Study:

• To develop a novel two-step procedure for crosslinking polybutadiene (PBD) as a sustainable alternative to traditional vulcanization.
• To create deconstructable soft materials from PBD that enable alternative recycling pathways.
• To achieve tunable material properties by controlling crosslinker identity and density.

Main Methods:

• Utilized C-H allylic amination of PBD to synthesize thermoplastic elastomer pre-polymers functionalized with hexafluoroisopropyl sulfamate (PBD-HFIPS).
• Employed alcoholysis of PBD-HFIPS with diol crosslinkers to form thermoset specimens.
• Investigated the cleavage of sulfamate crosslinks using nucleophiles to regenerate the thermoplastic.

Main Results:

• Successfully synthesized PBD-HFIPS pre-polymers and formed tunable thermoset materials.
• Demonstrated that material properties (thermal, rheological, mechanical) can be adjusted by varying crosslinker type and concentration.
• Showcased the efficient regeneration of virgin-like PBD from the thermoset by cleaving sulfamate crosslinks with a nucleophile.

Conclusions:

• The proposed two-step method provides a viable route to create recyclable thermoset elastomers from PBD.
• This approach offers a sustainable alternative to conventional rubber recycling, enabling closed-loop reprocessing.
• The ability to deconstruct and regenerate the original thermoplastic without degradation opens new possibilities for rubber material circularity.