Self‐Expansion Behavior of Silk Fibroin Film

Abstract

Abstract Summary: Silk fibroin cast film was prepared using a ternary solvent system of CaCl 2 /CH 3 CH 2 OH/H 2 O (1/2/8 in mole ratio). A drying temperature at casting influenced crystal structure of fibroin. When a drying temperature was set lower than 9 °C, the cast film became amorphous. When a drying temperature was set higher than 40 °C, a fibroin film of silk‐II structure was obtained. In order to produce a fibroin film of silk‐I structure, a preferable temperature range was from 20 to 26 °C. The crystal transformation from random coil structure into silk‐I could be made through exposure of an amorphous film to water vapor. As for the crystal transformation from silk‐I into silk‐II, the treatment with a glycerin solution was effective. In the course of the treatment a film showed self‐thinning and self‐expanding. The expansion ratio exceeded 40% at maximum. The film produced accompanying self‐expansion was ductile in nature. The apparent self‐expansion percentage as a function of initial thickness of the film. The ductility of the film was classified into four stages from the observation of recovery behavior after folding: •, very soft; ♦, soft; ▪, middle; ▴, hard (see Figure 5 ). image The apparent self‐expansion percentage as a function of initial thickness of the film. The ductility of the film was classified into four stages from the observation of recovery behavior after folding: •, very soft; ♦, soft; ▪, middle; ▴, hard (see Figure 5 ).