The increased ε r can be attributed to the formation of various nanocapacitors consisting of SRG sheets separated by dielectric PVDF film [36–38]. At 1 kHz, the dielectric constant of pure PVDF is 7. This value reaches 60 and 105 when the PVDF was filled with 0.4 and 0.5 vol.% SRG, respectively. Although carbon-based polymeric composites with high dielectric permittivity have been reported [35, 39–41], the dielectric loss of those composites are generally too large for practical

applications. In contrast, the electrical conductivity of the SRG/PVDF composite (for p = 0.4 or 0.5 vol.%) is relatively low (see Figure 4b); therefore, the dielectric loss can be minimized. The good dielectric performance Selleckchem Enzalutamide in combination with high flexibility makes such SRG/PVDF composite an excellent candidate of high-k material. Figure 4 Frequency dependency of (a) dielectric constant and (b) electrical conductivity of SRG/PVDF composite with various filler contents. Inset in (a) shows dielectric constant versus frequency plots for the composites with 0.1, 0.2, and 0.3 vol.% SRG. Figure 4b shows the variation of conductivity with frequency for SRG/PVDF composites. For the composites with low SRG loadings (p ≤ 0.3 selleck screening library vol.%), σ(f) increases almost linearly with frequency, which is a typical characteristic of insulating

materials. When the filler content reaches 0.4 vol.% and above, σ(f) at low-frequency region shows a marked increase, due to the onset of the formation of percolating structure spanning the polymer matrix. For the composites with higher SRG loadings (p ≥ 0.8 vol.%), the conductivity is independent of the frequency at low-frequency regime. Above a characteristic frequency, the conductivity increases with increasing frequency. This indicates that a percolating Tolmetin SRG network throughout the whole system has been fully developed. The frequency-independent plateau is termed as the DC conductivity (σ DC) and particularly obvious for the composites with high SRG loadings. The two-stage conductivity behavior can be described by

the following relationship [42, 43]: (2) where A is a constant depending on temperature and x is a critical exponent depending on both frequency and temperature. This behavior is typical for a wide number of conducting composite materials [42] and usually termed as ‘universal dynamic response’ [43, 44]. Ezquerra et al. have had a detailed study of such a behavior [45–47]. We have also investigated this dynamic response in carbon nanotube/nanofiber based composites [48, 49]. By fitting the data in Figure 4b to Equation 2, the values of σ DC, A, and x for percolative SRG/PVDF composites could be extracted. They are listed in Table 2. Table 2 AC electrical transport properties of percolated SRG/PVDF composites Filler content A B n value 0.4 vol.% 2.43×10−9 ± 2.12×10−10 1.42×10−11 ± 7.14×10−12 0.88 ± 0.01 0.5 vol.% 3.40×10−9 ± 8.13×10−10 3.23×10−11 ± 8.04×10−12 0.86 ± 0.01 0.8 vol.% 8.