Modified dielectric properties of poly(vinylidene fluoride) via 2S fraction of soy protein

Soy protein, as a naturally available resource, has been widely studied as a functional material. Major 7S and 11S fractions of soy protein have drawn the most attention. In contrast, the 2S fraction, a component with low molecular weight, has rarely been explored in material applications. This study investigated the 2S fraction of soy protein as a functional modifier to tune the dielectric properties of poly(vinylidene fluoride) (PVDF). It is found that 2S protein could efficiently modify the crystallinity and crystal phases of PVDF, depending on the concentration of 2S protein. The variation of crystal structures and hydrophobic PVDF-2S interaction led to remarkably altered dielectric properties of PVDF/2S films, evaluated by both ferroelectric hysteresis and impedance analyses. Dielectric polarization of PVDF/2S films was enhanced as the concentration of 2S protein increased; meanwhile, high 2S protein content led to high hysteresis loss, which should be related to the increased electrical conductivity of PVDF/2S films. (c) 2018 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018, 135, 46882.