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

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.