Synthesis, Structure, Properties and Applications of Electrospun Poly (Vinylidene Fluoride) - Functional Nanofiller Composites

Abstract

Electrospun poly(vinylidene fluoride) (PVDF) based nanocomposites were synthesized for various applications. Incorporation of nanofillers [halloysite nanotubes (HNT), polyaniline (PANi), graphitic-carbon nitride nanosheets (g-C3N4)] not only reduced the diameter of the PVDF nanofibers, but also improved the morphology of nanofibers. Fourier transform infrared spectroscopy, wide-angle X-ray diffraction and differential scanning calorimetry techniques were used to characterize the crystallinity, polymorphism and polymer-filler interaction in the electrospun PVDF nanocomposites. HNT and g-C3N4 acted as nucleating agents and helped in the formation of the -phase of PVDF. The primary objective was to explore the potential of electrospun PVD/HNT nanocomposite, PVDF/g-C3N4 nanocomposite, PVDF/HNT/PANi blend nanocomposite and PVDF/g-C3N4/PANi blend nanocomposite for piezoelectric force sensor, energy harvesting, battery separator and gas sensing applications. The inclusion of nanofillers and electrospinning synergistically improved the mechanical and piezoelectric properties. However, the degree of crystallinity decreased due to the hindrance to the polymer chain mobility. PVDF/HNT nanocomposite exhibited piezoelectric voltage and current output of 0.95 V and 32 nA, respectively. Addition of PANi to PVDF/HNT nanofibers significantly improved the electrical conductivity and piezoelectric properties. Electrospun PVDF/HNT nanocomposite was used in lithium-ion batteries (LIB) due to its relevant characteristics as gel polymer electrolytes (GPE). The GPE showed high ionic conductivity, electrolyte uptake and improved chargedischarge performance. The GPE outperformed commercial Celgard®2400 and pristine PVDF nanofibers in every aspect investigated. The highest -phase content of 97% was attained by electrospun PVDF/PANi/g-C3N4 blend nanocomposite (PPBF). The PPBF was used for energy harvesting from human locomotion and nitrogen dioxide (NO2) gas sensing. Flexible PPBF based nanogenerator exhibited excellent piezoelectric performance and was capable of generating a voltage and current output of ~30 V and 3.72 A, respectively, which could play a prominent role in energy harvesting application. Further, the PPBF based gas sensor showed excellent response to NO2 gas along with high sensitivity, selectivity, durability and reproducibility. The PVDF based nanocomposite non-wovens developed in this study are potentially useful as a force sensor, energy harvesting nanogenerator, GPE and gas sensor. Flexibility, low cost, non-toxicity, eco-friendliness and industry scalability are added attractive characteristics of these electrospun PVDF nanocomposites.