Charge distribution in PVDF/PMMA blends under DC field

The charge distribution in poly(vinylidene fluoride) (PVDF)/poly(methyl methacrylate) (PMMA) blends under direct current (DC) electrical field was measured by the pulsed electro-acoustic method (PEA). It was found that the field distribution tended to be uniform and the amount of charges were much smaller than the values estimated by the ordinary additive rule in the PVDF/PMMA blends. Differential scanning calorimeter (DSC), wide-angle X-ray diffraction (WAXD), dynamic mechanical thermal analysis (DMA) and scanning electron microscopy (SEM) were employed to investigate the miscibility and phase structures of PVDF/PMMA blends. The results show that the amorphous regions in the blends comprised amorphous PVDF regions and the miscible PVDF/PMMA regions. At low concentrations of PMMA, the miscible domains were separated and could not transport charges effectively. When the PMMA concentration increased, more and more miscible domains became a continuous phase, and charges could be transported easily and effectively through the miscible phase because polar groups of PMMA could act as hopping sites for charge transportation. Therefore, the decrease in charge amount could be attributed to changes of phase structure and excellent miscibility of the blends.