Getting self-healing ability and ultra-low dielectric loss for high-k epoxy resin composites through building networks based on Li0.3Ti0.02Ni0.68O grafted carbon nanotube bundles with unique surface architecture

Abstract Getting self-healing ability and ultra-low dielectric loss is effective to achieve high service reliability and sustainable development for high dielectric constant (high-k) polymer composites. Herein, new functional fillers with special surface architecture (sLTNO@mAC) were synthesized by grafting Li0.3Ti0.02Ni0.68O particles (sLTNO) on surfaces of carbon nanotube bundles (mAC), which was then embedded in epoxy resin (EP) with disulfide bonds to develop new composites (sLTNO@mAC/EP). Compared with composites based on mAC (mAC/EP) or a blend of sLTNO and mAC (sLTNO/mAC/EP) with the same filler loading, sLTNO@mAC/EP composites have much higher dielectric constant and self-healing efficiency as well as much lower dielectric loss at the same frequency. For the composite based on sLTNO@mAC with 8.2 wt% of sLTNO, coded as sLTNO1@mAC/EP, its dielectric loss is only 0.02, about 1.1×10 -3 and 9.4×10 -3 times of that of mAC/EP and sLTNO/mAC/EP, respectively; meanwhile its dielectric constant (216.1, 100 Hz) is the highest value among self-healable dielectric composites reported so far, and sLTNO1@mAC/EP has higher self-healing efficiency (97.7%) than mAC/EP and sLTNO/mAC/EP. The mechanism behind these attractive properties reveals that dielectric properties of sLTNO@mAC/EP mainly depend on interface polarization, while those of mAC/EP and sLTNO/mAC/EP are mainly related to the integrity of conductive networks.