THE HEAT OF WETTING OF SILK FIBROIN BY WATER

Abstract

The heats of wetting by water of silk fibroin initially containing various amounts of adsorbed and desorbed water have been measured. These measurements along with the water vapor adsorption isotherm of Hutton and Gartside have been used to calculate the integral and differential heats, free energies, and entropies of adsorption. In contrast with cellulose, silk containing desorbed water evolves less heat than that containing adsorbed water. This fact suggests that any contribution by a heat of swelling term is very small for silk fibroin, so that the calculated thermodynamic properties probably can be assigned almost entirely to the adsorption process. The changes in the heats and entropies of adsorption appear to parallel the sequence of changes in film formation as revealed by surface area calculations.