The dielectric behavior and origin of high-k composites with very low percolation threshold based on unique multi-branched polyaniline/carbon nanotube hybrids and epoxy resin

New high-k composites based on unique multi-branched polyaniline (MSiPA)/multi-walled carbon nanotube (MWCNT) hybrids and epoxy (EP) resin were prepared. MSiPA/MWCNT/EP composite has much higher dielectric constant and lower dielectric loss than MWCNT/EP composite with the same loading of MWCNTs. Dielectric constant and loss at 100 Hz of MSiPA3/MWCNT0.4/EP composite are 2.4 and 3.3 × 10−3 times the value of MWCNT0.4/EP composite, respectively; meanwhile the percolation threshold of MSiPA/MWCNT0.4/EP composites is as low as 0.51 wt%, remarkably lower than that of available composites with coated MWCNTs. These attractive results are attributed to unique structures of MSiPA/MWCNT hybrids. The multi-branched structure, large polyaniline concentration and flexible Si-O chains make MSiPA have big ability to be coated on surfaces of MWCNTs through π-π interaction. Different from MWCNTs, MSiPA/MWCNT hybrids have good dispersion in EP matrix, forming more micro-capacitors and avoiding the loss of conductive currents. Equivalent circuits were built to further discuss the origin behind.