Preparation of water-repellent silks by a reaction with octadecenylsuccinic anhydride

Silk fibers and membranes were acylated with octadecenylsuccinic anhydride (ODSA) at 75°C for different times. Swelling N,N-dimethylformamide (DMF) and dimethyl sulfoxide (DMSO) and non swelling solvent media (xylene) were used for reaction. Silk membranes that reacted in DMF or DMSO displayed faster reaction kinetics and attained higher weight-gain values than fibers. The effect of the solvent on the reaction yield was increasing from DMSO to xylene. The moisture regain and water retention of silk fibers acylated with ODSA decreased significantly, regardless of the solvent system used. Accordingly the water repellency increased. Acylation induced an increase in the thermal stability of the silk fibers and membranes.