Reprocessable Covalent Elastomeric Networks from Functionalized 1,4-cis-Polyisoprene and -Polybutadiene

To obtain and maintain rubber properties such as elasticity, strength, creep, and chemical resistance, or stiffness over time, rubbers must be chemically cross-linked, mainly by sulfur vulcanization. However, the materials produced in this manner result in irreversibly cross-linked networks and are consequently difficult to recycle, which leads to large quantities of rubber waste each year. In this paper, a new route to synthesize reversibly cross-linked 1,4-cis-polyisoprene (PI) and -polybutadiene (PB) based on the Diels-Alder chemistry is investigated. Furan groups are first grafted along the polymeric backbone and at chain ends. In a second step, a bis-maleimide compound is added to the modified liquid material, leading to the formation of a thermo-reversible cross-linked elastomer. Mechanical properties of the resulting rubber can be easily tuned and depend on the bis-maleimide/furan ratio as well as on the nature of the polymeric precursor (polyisoprene vs polybutadiene). The good reprocessability of these materials was demonstrated by remolding them five times without any loss of properties between the first and the last cycle.

Automated summary

This paper investigates a new route to synthesize reversibly cross-linked rubber based on the Diels-Alder chemistry. By grafting furan groups onto the polymer backbone and adding bis-maleimide compound, a thermo-reversible cross-linked elastomer is formed. The resulting rubber has easily tunable mechanical properties and exhibits good reprocessability.