Tuning surface texture of thermoplastic polyurethane/silk fibroin composites by phase separation method

Silk fibroin powder made from waste silk has gained considerable attention because of its outstanding physicochemical properties. In this study, thermoplastic polyurethane/silk fibroin (TPU/SF) composites were successfully prepared by combining different phase separation methods. The transformation of porous to compact films prepared by vapor/nonsolvent-induced phase separation (V–NIPS) as well as solvent evaporation/nonsolvent-induced phase separation (E-NIPS) using binary solvents. The effect of the film-formation method on the morphology, structure, and performance of the composite films were investigated. Compared with the surface of E-NIPS composite films, that of V–NIPS composite films had many micron-sized craters. Furthermore, SEM and porosity analysis results further supported the proposed film-formation mechanism. Upon the addition of 30 wt% SF, V–NIPS5 showed good mechanical properties with a stress of 16.2 MPa, strain of 1241.2%, and toughness of 118.2 MJ/m3. E-NIPS25 also showed good mechanical properties with a stress of 25.5 MPa, strain of 1089.7%, and toughness of 144.7 MJ/m3. The strengthened interface interaction between SF and TPU was observed through the analysis of the fractured surfaces. Furthermore, the V–NIPS composite films showed good hydrophilicity and biocompatibility. This approach of constructing unique surface structures has potential applications in functional fields, such as development of bionic materials and biological cell adhesion materials.