Conformation transition kinetics and spinnability of regenerated silk fibroin with glycol, glycerol and polyethylene glycol

Abstract

In this article, time-resolved FTIR spectroscopy was used to study the effect of aqueous solutions of glycol, glycerol, and polyethylene glycol (PEG) on the kinetics of the conformation transition of regenerated Bombyx mori silk fibroin (RSF) solution. The kinetic curves showed that glycol speeded up the conformation transition more than glycerol while PEG 400 and PEG 2000 were incapable of inducing a conformation transition in RSF solution. Accordingly, we investigated the effect of a coagulation bath of glycol, glycerol, PEG 400, and PEG 2000 on the wet-spinning of RSF dope solution into regenerated silk fibers. All these coagulation baths produced RSF fibers with useful mechanical properties. These two sets of observations together with earlier papers from this laboratory suggest that to produce tough silk fibers the conditions in the coagulation bath must allow sufficient time for adjustment of silk proteins in the conformation transition process.