A facile route to prepare high−performance dielectric nanocomposites of poly(methyl methacrylate)/poly(vinylidene fluoride)/carbon nanotubes

A facile route to prepare high−performance dielectric nanocomposites of poly(methyl methacrylate) (PMMA)/poly(vinylidene fluoride) (PVDF)/multi−walled carbon nanotubes (MWNTs) is systematically studied. A 30 wt % solution of PMMA/PVDF/MWNTs mixture in a solvent of N,N−dimethylformamide (DMF) is dried isothermally at ca. 20 °C below the upper critical solution temperature. Cocontinuous structure is formed through spinodal phase separation during the solvent evaporation and the MWNTs are found to be exclusively localized in the PVDF phase of the blends. The experiment results show that phase-separation and selection of CNTs occur quickly, while the conductive network needs more time to be formed. The domain size of such cocontinuous structure is in the sub−micrometer range, which is much lower than that produced by melt processing. When the volume fraction of MWNTs is 2 vol %, the dielectric constant of the composites is about 100 (at 100 Hz) and independent of frequency (102−105 Hz). The thermodynamics and kinetics of the polymer blends and composites are also studied by DSC and DMA. The composites have excellent ductility, their elongation at break is above 150%. Compared with the melt−mixing process, this approach provides a general pathway to prepare high−performance dielectric polymer materials containing cocontinuous microscale and nanoscale structures.