Interfacial adsorption, viscoelasticity and recovery of silk fibroin layers at different oil/water interface

Abstract

Silk fibroin is verified as a good stabilizer for some oil-in-water emulsions, but the interfacial adsorption, viscoelasticity and stabilization mechanisms of silk fibroin at different oil/water interfaces were less reported. In this study, effect of silk fibroin concentration on the interfacial adsorption and viscoelasticity of silk fibroin at both dodecane/water and butyl butyrate/water interfaces were investigated. Higher protein concentration helps silk fibroin molecules to form well-organized network structures at the interface, with higher interfacial elasticity, quicker establishment of interfacial adsorption equilibrium and slower structure breakage at large strain. The nonpolar dodecane oil encourages microstructural rearrangements of the more hydrophobic silk fibroin and enhances the physical crosslinks within the interfacial networks, thus resulting in stronger interfacial elasticity, slower interfacial adsorption equilibrium and higher protein saturation concentration for the dodecane/water interface. The influence of silk fibroin concentration on the strain induced interfacial structure fracture also seems to be much stronger for the dodecane/water interface. However, after a nonlinear strain deformation, the fractured silk fibroin layers can merely recover partially for the dodecane/water interface except for very dilute silk fibroin systems, but can recover completely with more compact and elastic interfacial networks for the butyl butyrate/water interface.