Self-expansion behavior of silk fibroin film

Abstract

Silk fibroin cast film was prepared using a ternary solvent system of CaCl2/CH3CH2OH/H2O (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 ahn 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. © 2006 WILEY-VCH Verlag GmbH & Co. KGaA.