Effective structure regulation of poly(vinylidene fluoride) via soy protein isolate: A morphological study

Abstract

The microstructures of poly(vinylidene fluoride) (PVDF)/soy protein isolate (SPI) films were successfully modulated via denatured SPIs. While vegetable proteins have been extensively researched as functional biomaterials in fabrication of polymer blends, the diverse polymer-protein interactions because of complex protein structures have not received sufficient attention. In this study, the PVDF-SPI interactions were tuned by different denaturation treatments including heat, sonication, and chemical denaturation by 2-mercaptoethanol and sodium dodecyl sulfate, respectively. Phase morphologies, crystal structures of PVDF, and secondary structures of SPI were analyzed by scanning electron microscope, fluorescence imaging, X-ray diffraction, and Fourier transformed infrared spectroscopy. While 90 degrees C denaturation and sodium dodecyl sulfate led to nonporous structures, all other denatured SPIs produced distinctive porous structures. The crystallinity of PVDF was reduced to different degrees, depending on the denaturation of SPI. The distinctive microstructures of PVDF/SPI films indicated the diversity of PVDF-SPI interactions and its importance in functional polymer/protein blends.