Effect of coupling agent 2,3,4,5‐tetrafluorobenzoic acid modification on dielectric energy storage properties of <scp>PVDF</scp>/<scp>PMMA</scp>‐<scp>BaTiO₃</scp> nanocomposite films

Abstract In this paper, the carboxylic acid modifier 2,3,4,5‐tetrafluorobenzoic acid (F4C) was used to modify the BaTiO 3 (BT) nanoparticles, which acted as a coupling agent. The modified BT(F4CBT) nanoparticles, polyvinylidene fluoride (PVDF), and polymethylmethacrylate (PMMA) were used to make the modified nanocomposite films: PVDF/PMMA‐F4C‐BaTiO 3 nanocomposite films. The unmodified BT nanoparticles were used to make the unmodified nanocomposite films: PVDF/PMMA‐BaTiO 3 nanocomposite films. The modification effect of the F4C resulted in an increase in the amount of β‐phase and γ‐phase, a decrease in the amount of α‐phase, and a decrease in the overall crystallinity of the PVDF‐based nanocomposite films. The dielectric constant of the PVDF/PMMA‐F4C‐BaTiO 3 nanocomposite films reached a maximum value of 16.7 at a frequency of 100 Hz at 4 wt% F4C, which was 40.3% higher than that of the unmodified PVDF/PMMA‐BaTiO 3 films. The F4C content of 2 wt% PVDF/PMMA‐F4C‐BaTiO 3 nanocomposite films showed the lowest dielectric loss of 0.055, which was 56.7% lower than the unmodified PVDF/PMMA‐BaTiO 3 films. The breakdown strength of the PVDF/PMMA‐F4C‐BaTiO 3 nanocomposite films increased and then decreased with the increase of the F4C content, and the highest breakdown strength was 2800 kV/cm at 4 wt% F4C, which was 55.6% higher than the unmodified PVDF/PMMA‐BaTiO 3 films. The charging density of the PVDF/PMMA‐F4C‐BaTiO 3 nanocomposite films reached a maximum value of 20.65 J/cm 3 at 4 wt% F4C content, which was 394% higher than the unmodified PVDF/PMMA‐BaTiO 3 films. Highlights Modification of ceramic nanoparticles with carboxylic acid coupling agent. The dielectric properties of the modified nanocomposite film were significantly improved. Maximum polarization and charge/discharge density were greatly improved by coupling agent modification.