Investigation of rheological properties and conformation of silk fibroin in the solution of AmimCl

The conformation and eventual morphology of silk fibroin (SF) chains are crucial for the mechanical properties of SF materials, and are strongly related to the solvation step as a key stage in their processing conditions. In this work, a novel SF/AmimCl (1-allyl-3-methylimidazolium chloride) solution with unique properties is reported and compared with conventional regenerated SF aqueous solutions, based on an investigation of its rheological properties. The steady shearing behavior suggested that AmimCl is a good solvent for SF molecules, and shear thinning of semidiluted SF/AmimCl solution at high shear rates showed behavior similar to that in native spinning, which is due to the rearrangement and orientation of SF molecular chains. Fitting of experimental dynamic viscoelastic data to the Rouse model provided an effective method to estimate the molecular weight of SF. We believe that this work not only provides a better understanding of the relationship between properties of silk protein and aggregation states of their molecular chains, but also provides tools to fabricate high-performance SF-based materials.