Salt‐catalyzed reaction of phenyl glycidyl ether with silk fibroin

Abstract

AbstractThe addition reaction of phenyl glycidyl ether (PGE) with silk fibroin was investigated in the presence of various salts in different solvents at 40–130°C. Some water was required to make the epoxide react with silk padded with various salt solutions. The reaction rate increased with the salt and PGE concentrations and reached a maximum value at a certain concentration of the salt or PGE. Padding with solutions of thiosulfate, stannate, thiocyanate, bicarbonate, and cyanide resulted in large weight gains to 12%, dry crease angles of 138°, little moisture regains and low solubilities (up to 15%) in 3 N HCl and 1 N NaOH aqueous solutions at 65°C (1 hr). Histidine, lysine, arginine, aspartic and glutamic acids, serine, and tyrosine reacted. The weight gains decreased with increasing solubility parameter of the solvents used, reached a minimum value at about 10 or at the solubility parameter of the epoxide, and then increased with the parameter. The epoxide‐silk reaction may depend on the distribution of PGE between aqueous salt and an organic solvent phases, and on the swelling of the silk fibroin in aqueous salt solution or in various organic solvents. The mechanism for this epoxide‐silk reaction was discussed in the light of the observed phenomena.