The effect of interfacial interaction on the conformational variation of poly(vinylidene fluoride) (PVDF) chains in PVDF/graphene oxide (GO) nano composite fibers

Abstract

Polymers such as poly(vinylidene fluoride) (PVDF), and its copolymers with hexafluoropropylene (HFP), trifluoroethylene (TrFE) and chlorotrifluoroethylene (CTFE) are known to possess electroactive properties and have been studied for decades, enabling them one of the most promising candidates for wearable and smart textile applications. Nonetheless, the practical applications are still limited and are in the early stage of development because of poor mechanical integrity. In the current study, we have prepared PVDF/graphene oxide (GO) nanocomposite fibers by dry-jet wet spinning method at the GO concentrations of 0, 1, and 2 wt% with respect to the polymer weight. The as-spun fibers were drawn in the draw ratio (DR) range of 2 to 6.5, and the correlation between the PVDF chain conformation and the mechanical properties of the fibers upon drawing has been studied by 2D correlation spectroscopy (COS) of Fourier-transformed infrared (FTIR), wide-angle X-ray diffraction (WAXD), differential scanning calorimetry (DSC), and tensile testing. The PVDF/GO nanocomposite fibers exhibited that the mobile PVDF crystals were nucleated because it was based on the conformational defects and kinks due to the polar interaction between PVDF chains and functional groups of GO, whereas the control PVDF fiber showed the conventional conversion of crystal polymorphs (a and g phases to b phase). As a result, the nanocomposite fiber showed dramatically improved toughness (enhanced by 1123% at a DR of 2 and 120% at a DR of 6.5) as compared to that of the control fiber. Furthermore, the tensile strength and modulus of the PVDF/GO (2 wt%) fiber were 394 MPa and 4.6 GPa, respectively, while those of the control PVDF fiber were 295 MPa and 3.9 GPa.