Poly(vinylidene fluoride) Nanocomposites with Simultaneous Organic Nanodomains and Inorganic Nanoparticles

Nanostructured polymeric dielectric composites, based on poly­(vinylidene fluoride) (PVDF), conductive carbon black (CB), and an unsaturated ionic liquid (IL), 1-vinyl-3-ethyl­imidazolium tetrafluoro­borate ([VEIM]­[BF4]), were fabricated by melt blending and electron beam irradiation (EBI) methods. Our strategy forms simultaneous double nanophases in the PVDF matrix, that is, homogeneously dispersed CB nanoparticles and organic PVDF-g-IL nanodomains. The organic nanodomains were produced by microphase separation of the PVDF-g-IL chains from the PVDF matrix at melt state in the electron beam (EB) irradiated PVDF/IL-CB nanocomposites. Furthermore, the CB nanoparticles were fully adhered with these nanodomains, and novel structures with nanodomains@CB nanoparticle were achieved. Such nanodomains@CB nanoparticle structures showed a synergetic nucleating effect on the PVDF crystallization and led to the formation of dominant nonpolar α phases in the nano-PVDF/IL-CB composites. Because of the nanodomains adhesion of the CB nanoparticles, the nano-PVDF/IL-CB composites displayed a drastic reduction in dc conductivity compared with that of PVDF/CB and PVDF/IL-CB composites, respectively. Importantly, the resultant nano-PVDF/IL-CB composites exhibited significantly decreased losses relative to that of PVDF/CB, PVDF/IL, and PVDF/IL-CB composites. The structures of nanodomains@CB nanoparticle can be well responsible for this improvement of dielectric performance due to the fact that nanodomains confined the ion movements of IL in electric field and that their adhesion to the CB nanoparticle surfaces largely hindered the direct CB–CB nanoparticle contacts, thus decreasing their leakage currents. Our strategy not only fabricates PVDF/CB dielectric materials with good CB dispersion, higher dielectric permittivity, lower conductivity, and lower loss but also paves a new strategy for fabricating nanocomposites with double nanophases in polymer matrix.