Fabrication And Dielectric Characterization Of All-Organic Polyaniliine/Poly(Vinylidene Fluoride) Compsoites

The dielectric permittivities of conductor/polymer composites can be raised significantly by percolating effect when the volume fraction of conductive filler approaches the percolation threshold(f_c).These composites are attracting more and more attentions due to the low filler loadings and good processability brought by the polymer matrices.And they have potential to be used widely in electrical and electronic fields.The dielectric properties of these percolative composites are commonly influenced by the conductivities, the shape of fillers and adopted process route.In this paper,poly(vinylidene fluoride)(PVDF) and conductive polyaniline(PANI) were selected as the polymer matrix and the filler respectively.The solution-cast and solution-hotmoding processes were adopted to obtain PANI/PVDF composite.Dielectric properties of resultant composites were characterized and then compared.Firstly,To obtain the dielectric capacitor composites,solution-cast was adopted to fabricate PANI/PVDF composites.The influences of PANI contents (f_PANI) and the frequency on the dielectric properties were studied.The results showed that when the f_PANI was up to 0.05(higher than the percolation threshold f_c= 0.041),the dielectric permittivity of the hybrid film was as high as 456(at 100 Hz),the breakdown strength was 60 MV/m,and the energy density was 7.2 J/cm³,which was three times higher than that of neat PVDF. Moreover,the dielectric permittivity was frequency independent even for the composites with the f_PANI approaching to the f_C.The results of SEM and XRD revealed that PANI can disperse uniformly in the PVDF matrix,and that PVDF existed mainly as typicallyβ-PVDF,respectively.The percolative theory and microcapacitor model were employed to explain the results.This route was demonstrated to be effective to prepare the high energy density capacitor material used in the wide frequency range.Besides,compared to the solution-cast process,the resultant composites by solution-hotmoding show a much lower dielectric permittivity(456→242) near a little higher percolation threshold(0.041→0.045).And the dielectric permittivity depends on frequency and temperature most significantly when PANI loading approaches the percolation threshold and 1vol%respectively. Tunneling effect could be responsible for this phenomenon.