Improved uniaxial dielectric properties in aligned diisopropylammonium bromide (DIPAB) doped poly(vinylidene difluoride) (PVDF) nanofibers

Diisopropylammonium bromide (DIPAB) doped poly(vinylidene difluoride) (PVDF) nanofibers (5, 10 and 24 wt% DIPAB doping) with improved and tunable dielectric properties were synthesised via electrospinning. DIPAB nanoparticles were grown in situ during the nanofiber formation. X-Ray diffraction (XRD) patterns and Fourier transform infrared spectroscopy (FTIR) proved that electrospinning of DIPAB doped PVDF solutions led to the formation of a highly electro-active β-phase in the nanofibers. Electrospinning in the presence of DIPAB inside PVDF led to very well aligned nanofibers with preferred (001) orientation that further enhanced the effective dipole moments in the nanofiber structures. The dielectric properties of the composite nanofibers were significantly enhanced due to the improved orientation, ionic and interfacial polarisation upon the applied electrospinning process, ionic nature of DIPAB and the interface between the PVDF nanofibers and equally dispersed DIPAB nanoparticles inside them, respectively. The relative dielectric constant of the PVDF nanofibers was improved from 8.5 to 102.5 when nanofibers were doped with 5% of DIPAB. Incorporating DIPAB in PVDF nanofibers has been shown to be an effective way to improve the structural and dielectric properties of PVDF.