Completely self-assembled fiber composites

Abstract

Wheat gluten is hydrolyzed to low molecular weight proteins where some of the proteins self-assemble into high modulus fibers and the rest arrange around the fibers to form a polymer matrix so that the total material produces a fiber-reinforced polymer matrix composite. Self-assembly at 37 °C yields fiber composites with a modulus of 266 MPa. Self-assembly at 22 °C suppresses fiber formation resulting in polymer materials of much lower 20 MPa modulus. Fourier transform infrared (FTIR) spectroscopy results show both materials have similar β-sheet content of about 50% but the composites formed at 37 °C have increased hydrogen bonding. Hydrophobic interactions are also different in the 37 °C composite because it is hydrophobic interactions that drive self-assembly into large amyloid fibers. Scanning electron microscopy (SEM) shows that there is good interaction between the fiber and matrix because protein completely coats the fibers and no voids are observed at the fiber/polymer interface. Thermogravimetric analysis (TGA) shows that the 37 °C composite is more thermally stable at higher temperatures because of the increased intermolecular interactions and the presence of fibers.