Enhancement of PVDF Electroactive Phase Content—Effect of Plasticizer as an Additive

Abstract

Polyvinylidene fluoride (PVDF) is a functional polymer with highly desirable electrical and piezoelectric properties. Optimizing its piezoelectric performance requires modifications to its morphology, composition, and electrical characteristics. Plasticizers are commonly known to improve flexibility in polymer materials and are used to facilitate ion transportation in electrolytes, increasing the conductivity. However, inclusion of plasticizer to enhance piezoelectric behavior, primarily by adding flexibility, facilitating better dipole orientation and consequently inducing higher piezoelectricity, was little explored. This study investigates the effect of the addition of ethylene carbonate (EC) as a plasticizer on the piezoelectric performance of PVDF. The PVDF/EC films using the spin-coating method were fabricated with different concentrations of EC loading (from 1 to 9 wt.%). The morphology of the prepared samples was investigated using scanning electron microscopy (SEM) and polarized microscopy studies. The crystalline structure and phase changes were analyzed using Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), and Raman spectroscopy. The thermal behavior of the samples was analyzed through differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA). The electrical permittivity under different DC frequencies was investigated using an LCR meter. First of its kind, the incorporation of EC plasticizer demonstrates an enhancement of the β-phase due to inter-molecular bonding between the carbonyl group from EC and the hydrogen atom from PVDF, which is crucial for improved dielectric properties. The experiment proves the ability of EC to modify the crystalline structure of PVDF with only polymorphism, which is possible with 2 wt.% of EC in PVDF at 120°C of annealing temperature. These findings establish the potential of plasticizer integration as a cost-effective methodology for applications in sensors and energy storage devices.