Concentration-dependent conformation transition of regenerated silk fibroin induced by graphene oxide nanosheets incorporation

Regenerated silk fibroin (RSF)/graphene oxide (GO) nanocomposite has been substantially investigated due to its significant multifunctional potential. Here, in combination of micromorphology, crystalline conformation, dynamic mechanical property characterization, and Fourier self-deconvolution (FSD) quantitative analysis, we investigated the RSF molecular chains conformation transition induced by GO nanosheet incorporation, and its influence on the structural and mechanical properties of solution casted RSF/GO composite films. The GO nanosheet promoted the silk fibroin molecular chains conformation transition from random coil to beta-sheet structure, and a correlation between beta-sheet structure fraction and GO concentration was revealed. The beta-sheet structure fraction increases further improved the dynamic mechanical property of composite films. Moreover, based on nucleation-dependent aggregation of silk fibroin molecular chains, a mechanism considering the competition effect between GO concentration and its total surface area was proposed to explain the observed concentration-dependent conformation transition phenomenon. The study improves our understanding on silk fibroin conformation transition process in RSF/GO composite and would provide a valuable reference for the rational design of bioinspired multifunctional materials with enhanced mechanical properties. (c) 2019 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2019