Tuning Morphology of Poly(vinylidene fluoride) Nanofibers Produced by Electrospinning Technique

The morphology of poly(vinylidene fluoride) (PVDF) nanofibers, electrospun from dimethylformamide (DMF), was tuned considering the priority in liquid-liquid (L-L) and solid-liquid (S-L) (crystallization) phase separation events. To this end, electrospun fibers were collected on a vessel containing water as non-solvent bath. To change the timing in L-L phase separation, the distance of vessel from the nozzle (known as working distance) was varied. Further, travelling of jet in electrical field was followed by solvent evaporation as well as crystallization. The morphology of the produced nanofibers was characterized using SEM, FTIR, DSC and XRD analyses. The results showed that since crystals were formed prior to structure freezing, the S-L phase separation could account for morphology evolution before L-L phase de-mixing. However, S-L phase de-mixing could not impede L-L phase separation during electrospinning. In addition, the polar b phase crystals were formed in nanofibers and their fraction increased with increasing working distance. Hence, the produced web at high working distance was considered as an appropriate candidate for high-tech applications such as devices with piezoelectric capabilities.