Polysulfide polyurethane-urea(PSPU)-based self-healing dielectric composites with poly-dopamine and KH550 chemically modified carbon nanotubes

In this work, polysulfide polyurethane-urea (PSPU) elastomers with dynamic disulfide bonds introduced into both the soft and hard segments were synthesized. Carboxylated carbon nanotubes (CNT) modified with poly-dopamine and KH550 (KPCNT) were used as fillers, and an approach of solution casting was adopted to fabricate the composite films (named KPCNT/PSPU). In addition, the self-healing efficiency of KPCNT/PSPU composites is improved to 98%. The percolation threshold (fc) of KPCNT/PSPU (5.11 vol%) is about twice that of unmodified CNT/PSPU composite film (2.69 vol%). The dielectric constant of 4.74 vol% KPCNT/PSPU at 100 Hz is 141, about 23 times that of PSPU, as well as maintaining a low dielectric loss of 0.17. Furthermore, the CNT/PSPU composite with 2.45 vol% CNT has a dielectric constant of 82 at 100 Hz, while reaching a high dielectric loss of 0.72. It can be concluded that the excellent dielectric properties come from the micro-capacitor effect, interfacial polarization, the exchange of hydrogen-bonding networks as well as disulfide bonds within the PSPU.