Facile Preparation and Origin of High-k Carbon Nanotube/Poly(Ether Imide)/Bismaleimide Composites through Controlling the Location and Distribution of Carbon Nanotubes

The morphology (location and distribution) of conductive fillers in conductive filler/polymer nanocomposites has a decisive influence on dielectric properties of a composite, so with the same components, how to facilely control the morphology of nanofillers, build its relationship with dielectric properties of the composite, and clearly reveal the origin behind are still interesting challenges. Herein, a fixed loading (0.4 wt %) of multiwalled carbon nanotubes (MWCNTs) was embodied into an incompatible poly(ether imide) (PEI)/bismaleimide (BD) system to prepare a series of composites (0.4MWCNT/PEI/BD). As the PEI content increases, the structure of composite successively changes from sea-island to cocontinuous phase and phase inversion. More interestingly, MWCNTs prefer to selectively distribute in the BD phase, tend to enrich around the PEI dense zone, and arrange normally to the radius of the PEI sphere zone, so the morphology of MWCNTs and thus dielectric properties of composites can be facilely controlled. The dielectric constant and loss of 0.4MWCNT/PEI/BD composite with 10 wt % PEI are about 4.5 and 0.1 times the values of 0.4MWCNT/BD composite, respectively, overcoming the critical problem of available conductive filler/polymer composites. Different equivalent circuits were built for these composites, revealing the origin behind the method developed herein for controlling unique dielectric properties of 0.4MWCNT/PEI/BD composites