Ahmad Jamekhorshid

Polymeric dielectric materials have attracted considerable attention for film capacitors due to their low weight, flexibility, and cost-effective fabrication. In this study, PVDF, owing to its high dielectric constant (ε′), and PMMA, with its excellent thermal and chemical stability and low dielectric loss (ε″), were employed to prepare dielectric films. The objective of this research is to evaluate the effect of single-layer, trilayer, and blend architectures of PVDF and PMMA on achieving a high dielectric constant while maintaining low dielectric loss in polymer films. The samples were fabricated using solution casting and, when necessary, hot pressing. Structural characterization was conducted through Fourier-transform infrared spectroscopy (FTIR) and X-ray diffraction (XRD), while the thermal behavior was investigated using differential scanning calorimetry (DSC). Dielectric properties were further assessed by broadband dielectric spectroscopy (BDS). FTIR and XRD results revealed that thermal treatment and blending significantly affected the crystalline structure of PVDF, particularly by increasing the fraction of the α-phase. DSC analysis demonstrated that the crystallinity of PVDF was strongly influenced by the presence of PMMA in the blends; specifically, in the blend with a PMMA/PVDF ratio of 2/1, the crystalline structure of PVDF was completely suppressed during the second heating cycle. BDS evaluations indicated that single-layer PVDF films (both pristine and annealed) exhibited the highest ε′ values along with elevated ε″. For PVDF/PMMA blends, ε′ decreased while ε″ increased. On the other hand, trilayer architectures provided the most favorable compromise: notably, the trilayer structure with a PVDF middle layer (sample TL-MVM) showed the lowest ε″ in the low-frequency region, followed by the single-layer PMMA (SL-M) and the trilayer with a PMMA middle layer (TL-VMV). Overall, the findings highlight that multilayer architectures offer a more desirable ba