Tuning Dielectric\nProperties with Nanofiller Dimensionality\nin Polymer Nanocomposites

Polymer nanocomposites hold great potential as dielectrics\nfor\nenergy storage devices and flexible electronics. The structural architecture\nof the nanofillers is expected to play a crucial role in the fundamental\nmechanisms governing the electrical breakdown and dielectric properties\nof the nanocomposites. However, the effect of nanofiller structure\nand dimensionality on these properties has not been studied thoroughly\nto date. This study explores the critical relationship between nanofiller\ndimensionality and dielectric properties in polymer nanocomposites.\nWe fabricated polyvinylidene fluoride (PVDF) nanocomposites by incorporating\na range of carbon-based nanofillers separately, including zero-dimensional\n(0D) carbon black (CB), one-dimensional (1D) multiwalled carbon nanotubes\n(MWCNT), 1D single-walled carbon nanotubes (SWCNT), two-dimensional\n(2D) reduced graphene oxide (rGO), and three-dimensional (3D) graphite.\nThe frequency-dependent (1 kHz to 1 MHz) dielectric permittivity (<i>k</i>) of the nanocomposites at the same concentration of nanofillers\ndemonstrated a hierarchical order, with MWCNT showing the highest\npermittivity (∼400%), succeeded by rGO (∼360%), CB (∼290%),\nSWCNT (∼230%), and graphite (∼70%), respectively. The\ntemperature-dependent (50–150 °C) dielectric spectroscopy\nrevealed high <i>k</i> with increasing temperature due to\nthe enhanced dipole movement. However, their dielectric breakdown\nstrength and energy densities were not correlated to <i>k</i> and exhibited the following order: SWCNT > MWCNT > CB >\nrGO > graphite.\nAs the electrical breakdown depends upon the nanocomposites’\nmechanical strength, we correlated the mechanical properties with\nthe nanofiller dimensionality, and Young’s modulus followed\nthe 1D ≈ 2D > 0D > 3D order. These findings will provide\nfundamental\ninsights into designing tunable, conducive nanofiller-based nanocomposites\nin next-generation flexible electronics and capacitive energy storage\ndevices.