Renewable, Degradable, and Chemically Recyclable Cross-Linked Elastomers

Most commercial elastomers, typified by vulcanized natural rubber, are cross-linked polymers and as such cannot easily be reprocessed or recycled. While some are derived from renewable resources, the majority are produced from petroleum feedstocks and do not easily degrade. In this study, renewable elastomers based on β-methyl-δ-valerolactone were produced using two different methodologies: (1) tandem copolymerization/cross-linking with a bis(six-membered cyclic carbonate); (2) cross-linking of a linear poly(β-methyl-δ-valerolactone) homopolymer with a free-radical generator. The mechanical properties of these materials were investigated; tensile strengths of up to 12 MPa and elongations of up to 2000% were observed. Inclusion of a filler (fumed silica) was used to enhance the performance of the elastomers without significant loss of elasticity, with some composites exhibiting tensile strengths nearly double that of the neat elastomer. Aqueous degradation studies indicated that the materials were capable of degradation in acidic and basic conditions at 60 °C. Moreover, these cross-linked elastomers can also be chemically recycled, yielding monomer in high purity and yield (>91% and 93%, respectively).