Impact of PVDF/PEO blend composition on the β-phase crystallization and dielectric properties of silica nanoparticles incorporated polymer nanocomposites

Abstract

Polymer nanocomposite (PNC) films consisted of varying weight composition polymer blends of poly(vinylidene fluoride) (PVDF) and poly(ethylene oxide) (PEO) as host organic matrices incorporated with 5 wt% amorphous silica (SiO2) nanoparticles as inorganic nanofiller have been prepared by solution casting method. The alterations in morphology, PVDF polymorphism and relative fraction of β-phase crystals, degree of crystallinity, and the polymer-polymer and polymer-nanoparticle interactions with change of polymer blend compositional weight ratio (i.e., PVDF/PEO = 100/0, 75/25, 50/50, 25/75, and 0/100) have been investigated by the SEM, EDX, XRD, and FTIR measurements. The frequency dependent complex dielectric permittivity, ac electrical conductivity, and electric modulus of the PNC films are studied at room temperature by employing the DRS technique. The SEM images reveal that the spherulite morphology of PVDF/PEO blend structures incorporated with SiO2 nanoparticles is altered enormously with the change of polymers blend compositions in the PNC films. The XRD results of these PNC films confirm that the β-phase crystallization is considerably enhanced in the PVDF-rich PNC film but it decreases almost linearly with the increase of PEO amount in the host matrices of these films, and remains higher for the PNC films in comparison to that of the pristine polymer blend films. The degree of crystallinity of these PNC films enhances non-linearly with the increase of PEO concentration but it is found low as compared to that of the PVDF/PEO blend films without nanofiller. Dielectric dispersion in the frequency range from 20 Hz to1 MHz reveals that the interfacial polarization significantly contributed to the enhancement of dielectric permittivity in the audio frequency range of dielectric spectra of these PNC films. The addition of 5 wt% amount of SiO2 nanoparticles in the pristine PVDF and PEO matrices reduces the dielectric permittivity over the entire frequency range, whereas the presence of these nanofiller particles in the PVDF/PEO blend matrices based PNC films increases at radio frequencies which is predominantly due to enhancement of the β-phase crystals. The relaxation time values determined from the relaxation peaks exhibited in the loss part of electric modulus spectra confirm that there is an increase in hindrance to the PEO chain segmental dynamics with the increase of PVDF amount in the polymer blend compositions of these PNC films, whereas the dc electrical conductivity is found independent of the blend composition. The polymer blend compositional ratio dependent promising structural, dielectric, and electrical properties of these PNC films offer their suitability as tunable novel nanodielectric materials of multifunctionality for the flexible electronic devices.