Addition reaction of multifunctional epoxides with silk fibroin

Abstract

Abstract The reaction of di‐ and tri‐functional epoxides with silk fibroin was investigated in the presence of various salts in different solvents at 45–75°C. The reaction rates depend on the nature of the salts and the solvents used. Large weight gains (to 28%) were obtained in the reactions with ethyleneglycol diglycidyl ether, glycerol triglycidyl ether, and vinylcyclohexene dioxide catalyzed by thiosulfate, thiocyanate, cyanide, or chloride ions in such solvents as carbon tetrachloride, toluene, ethanol, and isopropanol. The weight gains in the silk/epoxide reaction were obtained mainly by the reaction of epoxide with the phenolic hydroxyl groups of the tyrosine residues, although lysine, histidine, arginine, and serine residues were found to react. The silk fabrics reacted with the epoxides were imparted with low solubilities in aqueous NaOH and HCl solutions without an appreciable decrease of moisture regain and flexibility of the fabric, and had much improved creaseproof properties.