Development of regenerated silk films coated with fluorinated polypeptides to achieve high water repellency and biodegradability in seawater

Abstract

In this study, we prepared silkworm silk films with fluorinated polypeptide coatings on their surface to achieve water-repellent silk materials. The silk films were smoothly and uniformly coated with the fluorinated polypeptides to give a transparent film. The contact angles of water droplets on the polypeptide-coated silk films were measured to investigate the ability of the films to resist water. The silk films coated with the fluorinated polypeptides exhibited higher contact angles compared to those of the uncoated silk film, indicating that the fluorinated polypeptides formed a hydrophobic surface on the silk film. The structure of the fluorinated polypeptides influenced the water-repellent ability, and the polypeptide containing both perfluoroalkyl chains and biphenyl groups imparted the highest water repellency. A biochemical oxygen demand (BOD) assay for the polypeptide-coated silk films in seawater revealed that the silk films showed high biodegradability in seawater even with the fluorinated polypeptide coating. The polypeptide-coated silk films provide not only high water repellency for practical use but also high biodegradability in marine environments.