Biodegradability of polyisoprene rubber cross-linked with poly(L-cysteine) cross-linker

• A novel cross-linked polyisoprene material was synthesized by thiol-ene reaction. • Poly( l -cysteine), a biodegradable cross-linker, was enzymatically synthesized. • The cross-linked polyisoprene exhibited high mechanical properties. • Higher biodegradability was achieved by cross-linking with poly( l -cysteine). • Microbial degradation of polyisoprene moiety was confirmed by infrared spectroscopy. Polyisoprene is biodegradable bio-based polymer as a main component of natural rubber. Cross-linking such as vulcanization enhances physical properties of natural rubber materials, while the cross-linked network structure severely deteriorates biodegradability. In this study, we synthesized a biodegradable polypeptide cross-linker to fabricate cross-linked polyisoprene. The cross-linked polyisoprene was prepared by thiol–ene reaction with poly( l -cysteine). The mechanical properties of the cross-linked polyisoprene ring sample were comparable to that of conventional peroxide-mediated cross-linked polyisoprene. The biodegradability of the cross-linked polyisoprenes was evaluated by biochemical oxygen demand test in the presence of Nocardia takedensis , a rubber degrading bacterium. The cross-linked polyisoprene with poly( l -cysteine) cross-linked structure showed higher biodegradability compared to peroxide-cross-linked one, indicating that the combination of polyisoprene backbone and polypeptide cross-linking structures facilitated biodegradation.