Fine structure and oxygen permeability of silk fibroin membrane treated with methanol

Abstract

Dissolved oxygen permeability, water content, crystalline structure, crystallinity, and density of silk fibroin membrane were measured as a function of immersion time of the membrane in 50 vol% aqueous methanol solution. Permeability coefficient and water content exhibited a minimum at the treatment time of 30 min. After the treatment of methanol the silk II crystalline structure appeared in the membrane. The density of the membrane decreased with increasing treatment time, although the crystallization proceeded in the membrane. These results indicate an existence of roughly molecular-packed space (void) among the crystals. The appearance of the minimum for water content was attributed to the development of the crystal and to the growth of the roughly molecular-packed space. In addition to these two effects, the chain immobilization effect associated with the crystallization was taken into account to explain the minimum for the permeability coefficient.