Significantly enhanced dielectric properties and energy storage density for high-k cyanate ester nanocomposites through building good dispersion of pristine carbon nanotubes in a matrix based on in situ non-covalent interaction with phenolphthalein poly(ether sulfone)

Abstract

How to disperse pristine carbon nanotubes with non-covalent interaction for fabricating high-k polymer nanocomposites with low dielectric loss and high energy storage density (W_e) is still a big but interesting challenge. Herein, a fully compatible and transparent polymer blend consisting of phenolphthalein poly(ether sulfone) (cPES) and cyanate ester (CE) was specially designed as the resin matrix, and then new conductor/polymer composites based on multi-walled carbon nanotubes (MWCNTs) and CE/cPES were facilely prepared through melting blending. The structure, dielectric properties and W_e values of MWCNT/CE and MWCNT/CE/cPES composites were systematically studied. Compared with MWCNT/CE composites, MWCNT/CE/cPES composites have a much lower percolation threshold that is as low as 0.89 wt%, only about 0.25 times of that of MWCNT/CE composites; besides, MWCNT/CE/cPES composites possess greatly improved dielectric constants, much larger breakdown strength and W_e as well as greatly decreased dielectric loss. The origin of these desirable properties was discussed through investigating the structure and building equivalent circuits. Results show that an in situ non-covalent interaction is formed between MWCNTs and cPES during the melting blending process, while cPES is compatible with CE resin, so MWCNTs have excellent dispersion in the CE/cPES matrix, endowing MWCNT/CE/cPES composites with unique structure and desirable dielectric properties.