An environment-friendly chemical modification method for thiol groups on polypeptide macromolecules to improve the performance of regenerated keratin materials

The R&D and application of natural biomass resources is one of the important ways to solve the world's energy shortage and environmental pollution. However, the complex processing technology and poor mechanical properties seriously hinder the development of the biomass polymers. A kind of natural antioxidant, alpha-lipoic acid, was used to modify wool keratin by grafting thiols in this study, so as to ameliorated the physical properties of regenerated materials. The optimal process parameters and modification mechanism were explored. Research results indicated that grafting ratio of lipoic acid can reach more than 13% and the polypeptide chains were more stretched in solution, when 30% lipoic acid was added into keratin solution at 40 °C with a reaction time of 2 h. In addition, lipoic acid grafted on thiol groups can effectively weaken the intra- and intermolecular forces of keratin, this change made the arrangement of macromolecular chains more orderly. The physical structure of modified keratin became uniform and compact, and the materials had obtained better thermal and mechanical properties. This research provided a novel and environment-friendly method for the modification technology of keratin, and it was beneficial to expand the application fields of biomass materials.