Growth of Polyaniline Nanoneedles on MoS2 Nanosheets, Tunable Electroresponse, and Electromagnetic Wave Attenuation Analysis

The purpose of this work was to fabricate high-performance dielectric materials for electrorheological (ER) application and electromagnetic (EM) wave attenuation. Commercial MoS2 bulks were exfoliated into nanosheets via combination of ball-milling and bath sonication procedures, which were used as the template for in situ grafting of PANI nanoneedles (PANI-NDs) to afford MoS2/PANI-NDs. The length–diameter (L/D) ratio of PANI-NDs on MoS2 nanosheets was feasibly tuned via modulating the polymerization time. Therefore, the tunable electrical conductivity and dielectric properties of the obtained MoS2/PANI-NDs were achieved. Compared with bare MoS2 nanosheets, MoS2/PANI-ND-based ER fluids constructed more robust fibril-like structure governed by the external electric energy and exhibited higher dynamic yield stress (186.8 Pa at 3 kV/mm) with wider applied electric field strength (0–3.0 kV/mm). Furthermore, as a novel EM wave absorbing material, the maximum reflection loss (RL) values of MoS2 nanosheets reached −44.4 dB at 11.48 GHz with the thickness of 3.0 mm, while the similar RL values of MoS2/PANI-NDs (−44.8 dB) reached 14.5 GHz with the thickness of only 1.6 mm. The broad effective EM absorption bandwidth (RL values less than −10 dB) for MoS2/PANI-NDs was observed owing to the synergistic effect of PANI-NDs and MoS2 nanosheets.