A novel water-induced two-way shape memory polymer based on poly (L-lactic acid)/silk fibroin composites

A novel water-induced two-way shape memory polymer composite are prepared by introducing silk fibroin (SF1) with a certain secondary structure into poly(L-lactide) (PLLA). Bending test show that the incorporating SF1 and assisted ambient temperature endow the PLLA with water-induced two-way shape memory effect (2W-SME) and the maximum reversible conversion angle is approximately 33. In addition, the changes in angle can be repeated multiple times without applying any external force. Furthermore, the corresponding mechanism are investigated by the circular dichroism spectrum (CD), fourier transform infrared (FTIR) spectra and dynamic mechanical analysis (DMA). The results confirm that the secondary structure of SF1 plays a decisive role for the waterinduced 2W-SME of PLLA/SF1 composites. The reversible conversion of Silk I and Silk II in SF1 as well as hydrogen bonds between the SF1 and absorbed water molecules can be attributed to the water-induced 2W-SME of the PLLA/SF1 composites. This study provides a new view for developing water-induced two-way shape memory polymers and better understanding the water-induced two-way shape recovery mechanism based on the secondary structure transformation of SF.