Properties of silk fibroin/poly(vinyl alcohol) blend solutions and peculiar structure found in heterogeneous blend films

The gelation of aqueous poly(vinyl alcohol) (PVA) solution was accelerated by addition of a small amount of silk fibroin (SF). The peculiar structure found in heterogeneous SF/PVA blend films was analysed by polarizing microcopy, differential scanning calorimetry (DSC), infrared spectroscopy (IR), and scanning electron microscopy (SEM). The blend films (over 30 mu m thick) of SF/PVA (90/10 to 60/40 weight ratio) separated macroscopically into two phases: SF-rich and PVA-rich. SF-rich phases had many spherical particles (1-25 mu m). In the PVA-rich phases, a fabric-like plain weave structure was found microscopically under a dark field. The SF-rich and PVA-rich phases were analysed by DSC, IR and SEM. The phase separation is also discussed.