A one-pot preparation of silk fibroin modified with polyurethane micro-particles

Abstract

In this study, polycaprolactone (PCL) tetrol and 4,4′-methylenedi-p-phenyl diisocyanate (MDI) were initially mixed for 10 min at 40 °C, then immediately added to a silk fibroin (SF)–water mixture. The obtained mixture was then added into a mixer to prepare the modified SF. The effects of the polyurethane prepolymer (PUP) content in the modified SF on the structure and properties of the modified SF were investigated. Fourier transform infrared spectroscopy (FTIR) revealed that urethane linkages formed between the SF and the PUP, and that the grafting ratio of the PUP used for preparing the modified SF was 99.1%. Polyurethane micro-particles were dispersed throughout the SF matrix of the modified SF and interacted with the SF matrix through urethane linkages, which strengthened the interface between the two phases. This special structure led to improved strength and elongation of the modified SF at break. The urethane-linked SF and PUP improved the mechanical properties and gave a higher thermal stability than other materials prepared by physical mixing. In addition, compared with the pure silk fibroin, the modified SF demonstrated a higher strength and elongation at break, along with better flexibility and hydrophobicity. These properties were also improved as the PU content was increased. Therefore, a simple and effective method to prepare high performance modified SF was successfully developed.